Cam Check - for stock manifolds

[SneakyPete]

I am going to assign the current targetmaster motor in my boat anchor duty and upgrade to a better motor. Here's my situation, I am going to to keep the factory merc manifolds and risers for a while until I get the cash flow to step up. I will also upgrade the cam at that time. Until then, can you get give me some help. The two Comp Cams were recomended by their hotline for preventing reversion. The motor will most likely have Vortec heads with 9.1:1 CR and an aluminum Edelbrock RPM AIR GAP intake. Not sure quite yet on CFM for the carb. Still trying to figure things out before I buy.

Cam #1: Comp Cams Extreme Marine Hydraulic Flat Tappet p/n 12-232-3 "xm 256h" "Good I/O pleasure boat, skiing and good economy"
advertised duration: IN/EX = 256/262
@.050 IN/EX = 212/218
Lift IN/EX = .447/.462
LSA = 112

Cam #2: Comp Cams Extreme Marine Hydraulic Flat Tappet p/n 12-236-3 "xm 262h" "Biggest cam for I/O, good mid-range with excellent response, noticeable idle"
advertised duration: IN/EX = 262/268
@.050 IN/EX = 218/224
Lift IN/EX = .462/.477
LSA = 112

Cam #3: GM Performance Parts 350 HO CAM
advertised duration: IN/EX = 320/324
@.050 IN/EX = 212/222
Lift IN/EX = .435/.460
lobe centerline is 112.5 degrees

Cam #4: GM Performance Parts ZZ4 Cam
duration @.050 IN/EX = 208/221
Lift IN/EX = .474/.510
lobe centerline is 112.5 degrees

[SneakyPete]

Cam #4 is in there because I am kicking around the idea of dropping a ZZ4 crate motor in. I know...I know...but my boat has FWC, and I would put inconel exhaust valves in.

[vinny p.]

112* lobe seperation is too tight for stock exhaust. You will have reversion problems. The lift and duration seems good, just have them open up the lobe seperation to 114 or even 115 to make sure.

[SneakyPete]

How will openeing up the LSA affect power, does it put it in a different spot in the power band etc? Will it affect the lope of the idle (I would like some chop)? I have a desktop dyno coming in a few days so I will be able to fiddle around some before I make a final decision. Thanks for the help Vinny!!

[vinny p.]

A tighter lobe seperation cam is generally used for a motor where a higher power band is desired. In your case, as is with the rest of us building marine engines, we dont need to make power at high rpm. Most of us are targeting below 6000 rpm for max horsepower. My 540 is built for max horsepower @ 5800 and max torque @ 4500. I am running a 114* lobe seperation with full dry CMI's. Being that I have dry exhaust, I could certainly have gone tighter. The reason I didnt is because of the shifting of the power curve.
The advantage to a tighter lobe seperation is that it will allow the motor to rev up a bit quicker. But, remember what Einstein said, every action has an equal or opposite reaction. In this case, the horsepower and torque curve moves to a higher rpm. That doesnt help us here. When I build a car drag race motor, I go with a tight lobe seperation. Especially if its a stick car.
To answer your last question.. Yes, opening up the lobe seperation will smoothen out the idle. In a boat, thats a good thing. I assume you have an Alpha drive. You dont want to be shifting it at any higher rpm than you have to. Bravos arent any better. The last thing I want is the motor stalling while docking. When these boats are rigged to go fast, docking sucks. Dont make it any worse with a lumpy cam.

[SneakyPete]

Man, you drop pure science!!
Thanks for all the help and patience!

[vinny p.]

Thats what we are here for... To learn from one and other. My knowledge is with motors and drives, maybe you can help me one day in whatever you know more about than me.

[bowtie]

I can only tell you what I am running and then you decide if it sounds like what you want. I have a built 355 (built in 1995) with cast iron Dart heads, forged flat tops (about 10.5 to 1), the factory original 1987 multi point EFI, and factory style cast iron manifolds with the regular 3" risers which run through some S curves and straight out the transom under the swim plarform (no mufflers and not through the lower unit) and this cam: http://www.cranecams.com/?show=browseParts&lvl=2&prt=5&...31&partType=camshaft (http://www.cranecams.com/?show=browseParts&lvl=2&prt=5&Vehicle_Type=Marine&Cylinders=8&Engine_Make=CHEVROLET&Year=1987&Engine_Size=305-350%20C.I.&partNumber=109831&partType=camshaft)
If that link does not work, it is a Crane Hyd roller, part number 10981. It has an advertised duration of 284/292 with 222/230 dur @ .050 and .509/.528 lift (int/ex), this cam is ground with 112 degrees of lobe seperation. I have no reversion issues with this cam and the stock exhaust (not sure what will happen when I go with some aftermarket exhaust) and this thing will idle in gear at 500 rpms with no issues. This combination made 424 FWHP and 445 FWTQ on an engine dyno with the stock EFI setup and ECU but with a set of dtno headers, back when it was built in 1995. I know this is a larger cam than some reccomend, but it works perfectly in my application. Good luck whatever you decide.

[vinny p.]

Bowtie,
I am very surprised that cam does not cause any reversion issues. You say you have stock manifolds and risers. Where does the water mix with the exhaust? Are the risers standard length? Where did your engine make peak horsepower and torque? The one big difference you have over azk4536 is that you are running EFI. That will certainly help your idle.

I had a small block powered boat before my current boat. I built a 354 for it. I had a Comp Cam extreme marine series flat tappet in it. 218*/224* duration @ .050, .462"/.477 lift, 112* lobe seperation. Stock manifolds, Imco M-73 risers. That motor would suck water back in like crazy. I had to pull the cam and change it for a 114*. Problem solved. That cam is smaller than yours.

[bowtie]

Vinny, I have never had the manifolds or risers off since I purchased the boat and this is only my 2nd I/O (the first being a slow 6 cylinder that I never even turned a wrench on and was bored with after the first summer), so I honestly do not know exactly where the water rejoins the exhaust. In fact, I suspected I might have had taller risers after reading the comments about reversion, but when I measured mine they were the short ones. In fact, I do not even think the tall ones would fit under the Ambassadore's engine cover. I do not know how to post a pics on this sight, but if you wanted to send me an email address I could send you a pic of the engine which shows the right side manifold and riser clearly and perhaps you could confirm what I suspect which is that they are either OEM or OEM replacements. One thing to consider which may help with the reversion in my case, is that immediately after exiting the riser, they turn down and run down to the transom exits which are below the swim deck. Also keep in mind, I only have through the transom exhaust with no mufflers or anything else to add restriction to the exhaust. As far as the HP and Tq numbers go, I do not have the dyno sheets here in front of me (I am at work)but if I remember correctly, the 424 HP was right around 5500 rpms (which is where they stopped the 2nd pull after the ECU reprogram) and peak TQ was around 4500 or so. Coincedentaly, before they replaced the ECU they pulled it all the way to 6000 rpms and the HP continued to increase, but was still less than what they got after switching to a new ECU. According to Crane, this cam should make power to about 6200 or something like that, but I do not know if this stock EFI would work up there.

[SneakyPete]

I have the same setup as far as exhaust, manifolds, risers, s -pipes, and exits that are at the water line, only the top 1/4 of the tips are above water. Vinny, that cam you had on the 354 (stroked 305?), what did you think of it? When you chnged to 114*, did you just have them cut a new cam with the same specs but just a different LSA? What did you think of that 2nd cam? What was your compression? If I go with the 350 HO ($2300), it is going to have 9.1:1, and if I go with a ZZ4 ($3700) or a circle track crate motor ($4k), it will have at least 10:1. I have to figure out my finances, and see if I can handle 4k for the latter 2. If I did go with one of the more powerful two, I would have to change the cam b/c I can't afford the motor and another 2k for exhaust. Also, I do have an alpha, but I would like to upgrade (sometime down the road) to a bravo with a stern jack (I plan to have the boat for a long time). I guess I am trying to say is that if I get the better motor now, I can just do it once, as opposed to doing it again when I want to go faster with new outdrive.

[vinny p.]

Bowtie,
My e-mail is checkmate259@earthlink.net Send me the picture. The risers dont necessarily have to be taller, they can be longer which dumps the water futher back.

azk4536,
The cam was only a flat tappet. They are cheap. I just had another one ground. A 354 inch Chevy engine is a .030 over 350, standard 3.48" stroke. My compression was 9.25. I can never even think of running higher with the fuel available on the water around here. 93 octane is available, but still wouldnt go beyond 9.75 max. My 540 is only 9.22 and thats with aluminum heads.
Be real careful when buying an automotive engine for your boat. Make sure it will work. If you are not sure ask for opinions first. First question I have for you is salt or fresh water? Post complete engine specs. Cast or forged internals, compression, cylinder head cc, valve material type, etc.. If you are looking to make a good piece and plan to keep it, go for a hydraulic roller cam, more money but better. Look into Isky cams and Morel lifters. I feel they are the best. I can explain if you want. Take a look at this site http://www.shafiroff.com/ He is here on Long Island. His prices are very competative. Look into his short block kits. He can send it to you fully assembled for the prices he lists. This way you can get a real solid short block specifically built for you. It may blow your budget, but it may give you an idea.
Switching from an Alpha to Bravo is not so simple. Not sure if your cutout will be ok, but definetly have to change the transom assembly. I would be careful about the sternjack idea. Talk to someone who has done this. It may move the weight to far back causing handling issues. Bravos already weigh more than Alphas.

[vinny p.]

I just re-read your post.. You can count on changing the cam in any crate motor you buy. It wont be optimized for marine use.

[SneakyPete]

It will be fresh water use, and the boat has Closed Loop Cooling. I believe that all 3 motors have Powered Metal Rods and "high silicon aluminum pistons." I don't do poker runs or run for extended periods of time WFO, but I would like to have it there when I want it if you know what I mean. With the motor I have now, it never sees more than 30-45 seconds wide open, cause I don't want it shooting rods through the block, then again it only pulls to 4000rpm with the auto cam it has, and the 23p cleaver (about 53mph on the speedo). I spend a lot of time lazizly cruising along on plane (2500rpms or so).
350 HO
SDPC Part Number: 12486041
Manufacturer: GM Performance Parts
Horsepower : 330 hp @ 5,000 rpm
Torque : 380 ft/lbs @ 3500 rpm
Compression Ratio : 9.1 to 1
Block : Cast Iron 4-bolt, 4.000" Bore
Crankshaft : Cast Nodular, 3.480" Stroke
Heads, Chamber Size : Vortec Cast Iron, 64cc Chamber
Valves (I/E) : 1.940"/1.500"
Camshaft, Lift (I/E) : 0.435"/0.460" Hydraulic
Dur. @ 0.050" (I/E) : 212/222 degrees
Intake : Not Included

ZZ4
SDPC Part Number: 24502609
Manufacturer: GM Performance Parts
Horsepower : 355 hp @ 5,250 rpm
Torque : 405 ft/lbs @ 3500 rpm
Compression Ratio : 10.0 to 1
Block : Cast Iron 4-Bolt Main, 4.000" Bore
Crankshaft : Forged Steel, 3.480" Stroke
Heads, Chamber Size : Aluminum, 58cc Chamber
Valves (I/E) : 1.940"/1.500"
Camshaft, Lift (I/E) : Hydraulic Roller, 0.474"/0.510"
Dur. @ 0.050" (I/E) : 208/221 degrees
Intake : Aluminum Dual Plane


Circle Track
SDPC Part Number: 12496769
Manufacturer: GM Performance Parts
Horsepower : 385 hp @ 5600 rpm
Torque : 385 ft lbs. @ 4000 rpm
Compression Ratio : 9.6 to 1
Block : Cast Iron 4-Bolt, 4.000" Bore
Crankshaft : Forged Steel, 3.480" Stroke
Heads, Chamber Size : Fast Burn, 62cc
Valves (I/E) : 2.000"/1.550"
Camshaft, Lift (I/E) : 0.474"/0.510"
Dur. @ 0.050" (I/E) : 208/221 degrees
Intake : Aluminum Dual

[SneakyPete]

Needless to say, these motors would spend more time than the current one at higher rpms, due to my increased faith in them holding together - but I still believe they would live a relatively easy life. My boat looks like it should do some pretty good speeds, and it is a disapointment to be getting the speeds I am currently getting.

[vinny p.]

Forget #2 as it is, too much compresssion. Maybe you can get it as a short block and use 62 cc heads, that would bring the compression down.

#1 has a cast crank. It will run fine, but not the best internals. Small valves, I would prefer 2.02 and 1.60 valves. While not necessary, Inconel exhaust valves are a great thing.

#3 sounds best. What is the cams lobe seperation? 9.6 compression is ok, if you can run 93 octane. I wouldnt run any lower octane with 9.6 and steel heads.
If you are going to run the roller cam that comes with the motor you MUST find out what material it is made of. Some are billet. Unless it is a trick cam that has a cast distributor gear pressed on the back, you would have to run a bronze distibutor gear. Those gears dont last. I have heard of some other distibutor gear that has become available, but not sure who makes it or about its longevity. I prefer the 2 piece cams. Billet lobes and cast gear pressed and pinned together. I used it in my 540 with no issues.

[SneakyPete]

I believe I have heard the term Melonized used in reference to the special distributor gear - is that it?.
#3 has aluminum GM fast burn heads.
#2 is available as a short block (it is the basis for the ZZ4 motor), $2189 from Scoggin Dickey.
http://www.sdpc2000.com/catalog/514/products/622/350-ZZ...-Engine-Assembly.htm (http://www.sdpc2000.com/catalog/514/products/622/350-ZZ4-4-Bolt-Main-GM-Performance-Parts-Short-Block-Engine-Assembly.htm)

Vortec heads seem like the way I will go, as they are lots cheaper than any other performance head. I read in Car Craft and Scoggin Dickey that stock vortec heads can only handle about .450 of lift. #1 has those heads but its cam has .460 of lift, and the cam I want to run has .477 of lift. Could I get away with this, or would I need to get the high lift vortec heads from SDPC? How much power difference would you say is between cam#1 and cam#2 provided the LSA was 114, and not 112.
Thanks again!!

[SneakyPete]

Crate Engine Depot says max lift for the vortec is .475 of lift....hmmmm

[vinny p.]

Bowtie,
I got your picture. Those are stock Merc manifolds and risers. The water mixes with the exhaust at about the middle of the of the rubber coupler connecting your riser to the elbow. While I have no experience with that set-up, I would imagine that the fact the pipes are straight down would help counteract any reversion. But, I am still very surprised that you have no reversion at all.

azk4536,
I dont know the answer to your questions regarding lift and those cylinder heads . I have never done any research on Vortec heads. It has been a while since I built a small block. Assuming that the limiting factor is port flow, I cant see that little bit of additional lift making a difference. I would be more concerned about making sure the additional lift doesnt cause the springs to go into coil bind. Just make sure that the springs are right for your cam. I trust no one when it comes to valve train. I always set up my own spring heights. I had a hell of a time with my Air Flow Heads on my 540. I was forced to buy complete heads from them. It was cheaper that way. I told them my spring requirements. When I got the heads, I popped them apart to find they had put very stiff springs with alomst twice the pressure I asked for. Needless to say, they were taken off and put on the shelf.

The best thing I can tell you to do, is to get exact head flow data and input it into a desk top dyno. That program works real well, but you have to enter very specific information to get accurate numbers from it. My engine was accurate to 20 hp and torque was dead on. The curve was a bit off, but very close. I should have saved the $$ spent on dyno time!!

[SneakyPete]

I just got my desk top dyno, it is the basic version from comp cams, and only allowed me to enter general info on the heads. Basically I picked the pocket proted stock heads, as I havent figured out how to enter cc's and volume yet (if you even can) but it has the engine putting out almost 425-450hp &480tq (depending on the exhaust I choose). Cam#1 had about 405hp and 450tq if I remember correctly.

[vinny p.]

The version I have allows me to enter actual head flow data at lift intervals of .100"

At what rpm does the hp and torque peak? You also want as flat a torque curve as possible.

[bowtie]

azk, with the Vortec heads, the first limiting factor to high lift camshafts is the springs. This is why the stock heads are only supposed to be used with .450 or so lift. You can get the Vortec's with upgraded springs and that will give you some more room to work with (maybe up to .525 lift but I would have to double check that) then you run into interference problems with the top of the valve guide and spting retainer. Also keep in mind that with the Vortec heads, in addition to having to have a Vortec style intake, you will have to have a set of late model rockers or a set of rockers designed for the Vortecs because they do not use an integrated pushrod alignment slot like the older GM S/B heads but instead use a self aligning or rail type rocker to align off of the valve stem. SDPC used to offer a set of reworked Vortec heads that had the guides trimmed down, larger springs, screw in studs with guide plates, and possibly larger valves if I remember correctly, but they do not list them anymore. I am a little suprised to hear your boat uses a closed loop cooling system, but if it truly does, I would strongly consider a set of the Edelbrock E-Tec aluminum (Vortec style) heads. They flow better than the GM Vortecs, come with screw in studs and guide plates and better springs from the get go. Also, a couple things to consider that I have not seen mentioned yet is that smaller motors and especially smaller bore motors are more tolerant of higher compression ratio's (i.e. where a 540 might have detonation problems with a 10-1 compression ratio, a 350 might not). In addition to that, smaller motors are a little less likely to have reversion issues with similar cam profiles than their larger brothers. Just wanted to throw that out there for you. In all honesty, if I were to build another motor for my boat it would be a 383. Have you considered the ZZ383 crate motor. Granted I would prefer to build my own and would only use Forged pistons over the use of Hypereutectic (sp) pistons, but if you wanted to buy one that would be a consideration. If I am not mistaken Edelbrock also offers a crate 383 with the Etec heads on them that makes like 460 HP. Good Luck.

[bowtie]

Coincedentally, the GM ZZ383 make 425 HP at 5400 rpms and 460 ft/lbs of TQ at 4500 rpms according to SDPC's website and it uses a cam that has the identical specs (duration at .050 and lift numbers) as the Crane cam in my boat and the one I posted the link to earlier in this topic. Of course they do not advertise that it is a Crane cam, and without seeing a full cam spec sheet it is impossible to tell exactly how close they are to being the same, but from what info is given they are fairly damn close.

[happy]

the bravo transom assembly will bolt right into where the alpha assembly goes.. i sure would look at that 383 package mercs got out there.. its a deal... comes with engine/drive/ shield, trim pump.. its gotta lotta bang for its buck!!

[SneakyPete]

I was thinking about those SD modified vortecs, they have a kit that comes with the heads (w/ rockers, gaskets and bolts), Edelbrock Air Gap intake (w/ gaskets and bolts) all for $1009. That is a great deal, but the $2300 for the 350HO long block is pretty sweet, all I would need would be an intake for $225, and a cam and lifters for like $240. Total outlay is approx $2700, where if I went with the short block and SD kit it would already be at $2500, then I would need cam, cam chain, timing cover, oil pump and pickup, oil pan etc etc. I do really like the look of the E-tecs though, perhaps I should hold off and gather some more coin, or just buy things one at time and play the waiting game...

[bowtie]

One last option for you to consider and most likely the one I would go with if I was in your identical position is the HT383... This is a high torque stroker that GM came out with for trucks and tow vehicles, and it would not suprise me the least if it is the long block Mercruiser uses for it's 320 HP 6.2 MPI. This crate motor goes for $3998.00 at SDPC and comes complete from intake to oil pan and includes cast iron Vortecs and a small hyd roller camshaft, it makes 325 HP at 4500 rpms and 415 ft/lbs of TQ at 3500 rpms. Of course with a cam and spring change you could help those numbers out considerably, but then it might not justify the cost savings over the ZZ383 (the ZZ383 is about $800.00 more but does not include the intake; however make 100 more HP and 45 more ft/lbs of TQ).

[SneakyPete]

I just upgraded my Desktop Dyno. I got these flow numbers from Kendrick Auto.
Intake Exhaust
Lift CFM
0.050 37.6 26.3
0.100 68.1 51.8
0.200 136.1 105.9
0.300 193.1 134.8
0.400 222.8 144.4
0.450 228.8 146.8
.0500 228.8 147.6
0.550 225.8 149.2

Desktop Dyno Results
Cam #2
471HP/449Tq @5500rpm - A max HP of 551 comes at 7500 RPM(!!) Torque is nice and flat, 2k = 118hp/311tq, 3k = 310tq/177hp, 4k =375tq/286hp, 5k = 447tq/426hp

Cam #1
492hp/470tq at 5500rpm. The curves look similar.

Why do these #'s seem outrageously high? I ran the program using small tube headers/no mufflers. Which do you think best resembles my exhaust setup, stock manifolds and mufflers, hp manifolds & mufflers, small tuber headers and mufflers, or small tube no mufflers.
Whe I ran it again with HP manifolds and mufflers (I figure this resembles my system of restrictive stock manifolds and no muffers) I got 410hp and 391tq on Cam #1, and Cam#2 dropped to about 390hp. These numbers seem more reasonable. What do you all think?

[SneakyPete]

Right now I think I will go with the 350HO crate motor, and put cam#1 in it, but have Comp Cams grind it to 114 LSA. I will use a Edelbrock Aluminum Air Gap Intake. Seems like good power for the money.

[SneakyPete]

Bowtie, what kind of speeds are you getting and with what prop? Is the Ambassador a faster or slower hull than an Enchanter?

[bowtie]

It runs right around the 70 mark GPS (71.8 GPS with a Turbo 24" 3 blade with 1/2 tank of gas and 2 adult men, 70.8 with a 3 blade Hydromotive and a full tank of gas with myself, my girlfriend, 2 teenage girls, and one little boy). Not sure which is considered a faster hull, I am not familiar with the Enchanter. From the pics it appears to be smaller than the Ambassadore, also the Ambassadore is an open bow (well as open as they get for a Checkmate).

[bowtie]

AZK, you may want to make sure that the HO 350 comes with a roller camshaft and not a flat tappet. If not, you will have to buy the hydraulic roller setup to convert to a roller camshaft and that will run another $220.00 (factory roller lifter, guides, spider, and screws), you may also have to drill and tap the bosses in the lifter valley if they were not done from the factory. Also, that motor comes with a cast crank, not sure about the rest of the rotating assembly.

[bowtie]

OK, just found the specs for the Enchanter... It looks like it is a foot longer than the Ambassadore, but 250-300 lbs lighter and appears to be a lower profile boat. Still not sure which would be the faster hull, but i suspect it would be the Enchanter with equal HP.

[SneakyPete]

That motor comes with a hydraulic flat tappet. The cam I want to use is also a hydraulic flat tappet, so I should be okay (I think). Should I buy just the cam, or should I get the kit that has the cam and lifters so I can use Comp Cams Lifters?

[vinny p.]

Also, a couple things to consider that I have not seen mentioned yet is that smaller motors and especially smaller bore motors are more tolerant of higher compression ratio's (i.e. where a 540 might have detonation problems with a 10-1 compression ratio, a 350 might not). In addition to that, smaller motors are a little less likely to have reversion issues with similar cam profiles than their larger brothers

Bowtie,
I have never heard of this. I dont claim to know it all, but can you tell me why this would be?

azk,
Get the complete kit from Comp. You HAVE to change the springs anyway. They most likely wont be right. At the very least, check them. Those dyno numbers seem a bit high to me also. The last set look more reasonable. Where are you located? If you need or just want, I would be glad to go over those heads for you. Glad to see that you are going with the 114* cam. Did it change the curve much from 112*?

[SneakyPete]

I live in Northern VT and you are in LI, so we are a ways away, but if you ski or snowmobile and are ever in the area come on by!! To get the 114LSA, if just played with the #'s on the cam until the Desktop Dyno showed 114. I actually picked up a few ponies when I did it!! The curve stayed pretty close if I recall. I have the #'s written at home and will post them when I can if you don't mind checking them. I am definately going to pull the heads off and put inconel ex. valves in there (who and where from do you recomend?) just so the thought of a valve breaking off is not in the back of my head. I have never pulled a head apart, so I will definately hit you up for help. Thaks again!!

[vinny p.]

You cant simply change the exhaust valves for Inconel. You would have to cut the angles again. Setting up the spring heights is easy if you have the right tools. You need a spring compressor and a height mic.
http://www.jegs.com/webapp/wcs/stores/servlet/CategoryD...ryId=10797&langId=-1 (http://www.jegs.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10002&storeId=10001&categoryId=24223&parentCategoryId=10797&langId=-1)

[vinny p.]

Oh, you will need a spring tension tester also. I used Ferria valves in my AFR heads. I got them directly from AFR. Manley has Inconels also.

[bowtie]

Originally posted by vinny p.:
[QUOTE]Also, a couple things to consider that I have not seen mentioned yet is that smaller motors and especially smaller bore motors are more tolerant of higher compression ratio's (i.e. where a 540 might have detonation problems with a 10-1 compression ratio, a 350 might not). In addition to that, smaller motors are a little less likely to have reversion issues with similar cam profiles than their larger brothers

Bowtie,
I have never heard of this. I dont claim to know it all, but can you tell me why this would be?

Vinny, as far as why the reversion problem is more pronounced on larger engines, I can only guess that it is due to the stronger negative wave created during overlap. All I know for sure is that I read about it on one or more sites when I was researching exhaust for my boat. As for the compression ratio's, larger bore motors have a much larger combustion chamber which requires more time for the flame travel to cover which gives detonation more time to occur, also the larger combustion chambers allow for more hot spots which can also lead to detonation problems. Lastly, the actual culprit for detonation problems is cylinder pressure not the ratio, larger motors tend to generate higher cylinder pressures with equal compression ratio's than smaller motors, given equivelant valve timing events.

[vinny p.]

As for the compression ratio's, larger bore motors have a much larger combustion chamber which requires more time for the flame travel to cover which gives detonation more time to occur, also the larger combustion chambers allow for more hot spots which can also lead to detonation problems.


Bowtie,
I dont agree. Detonation is too fast of the burning of the air/fuel mixture. If what you say is true, a larger bore engine would be less likley for detonation.

{quote}Lastly, the actual culprit for detonation problems is cylinder pressure not the ratio, larger motors tend to generate higher cylinder pressures with equal compression ratio's than smaller motors, given equivelant valve timing events.{quote}

I agree with this partly. Yes, cylinder pressure is what causes detonation, not static compression. But, the biggest factor in determining cylinder pressure is static compression. While valve overlap is a factor, the size of the bore doesnt figure into the equation.

[SneakyPete]

I found this cam on the Comp Cams site, can you tell me what you think? It has 114* LSA off the shelf, so it saves me the hassle of a custom grind. On the DD it spits out 430hp at 5500rpm, and 435tq at 4500rpm. It has at least 340tq at 2000rpm and rises to 435tq at 4500rpm, nice and flat torque curve, so it seems pretty good.

HYDRAULIC: Good for TPI 305 or 350 with aftermarket chip and upgraded exhaust.

Camshaft Specification Table
Part Number 12-262-4
Engine 1955-1998 Chevrolet
262ci-400ci
8cyl.
Grind Number CS XE262H-14
Description

--------------------------------------------------------------------------------

Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.464 0.47
Duration At 0.006 Tappet Lift 262 270

--------------------------------------------------------------------------------

Valve Timing At 0.006
Open Close
Intake 21 61
Exhaust 73 17

--------------------------------------------------------------------------------

These Specs Are For The Cam Installed At 110 Intake CL
Intake Exhaust
Duration At 0.05 218 224
Lobe Lift 0.309 0.313
Lobe Separation 114

--------------------------------------------------------------------------------

Recommended Valve Springs 983-KIT

[vinny p.]

The only thing I dont like about that cam is that its a flat tappet. Other than that, as long as your desk top dyno and Comp Cams like it, go for it.

[bowtie]

Call Comp and ask them what they think... I see that one is very similar to their "Marine" camshaft except the "Marine" one has 112 lobe seperation and slightly more exhaust lift. For what it is worth, sometimes a slightly narrower lobe seperation will help with the signal to the carb... if you are fuel injected this is not necessary.

[SneakyPete]

What do you mean by "signal to the carb"?

[happy]

here's one for ya... x race boat.2002 model just ripped two engines down a sealed 575..... and its a flat tappet. go figure??? here is the kicker the block is set up for a roller.. <<< my ??? is why???

[vinny p.]

Happy,
I am very surprised. Were those motors stock Merc motors with roots style blowers? Just trying to make sure I knnow which motors you are talking about.


azk,
The only thing I can figure that Bowtie is talking about by "signal to carb" is vaccuum. If this is the case, then take 2 cams with the identical lift and duration one ground on a 112* lobe seperation, the other at 114*. While the difference is not extreme, the 112* cam will have more valve overlap than the 114*. That will cause a rougher idle and less vaccuum.

[happy]

I was really shocked to see the 575 with a flat tappet.. and yes it has the roots style blower.. since the boat raced for a season, and the bands were still on the engines, they had never been opened up..

these engines have 250 hrs on em.. and the owner wanted to do a top half, upon the look see inspection of the cylinder walls, we decided to go ahead and freshen up both the engines.

[vinny p.]

Happy,
Good luck with those motors. Just in case you didnt know, I have heard that kits are available for that motor which you can get a superchiller and add more boost to get more power.

[bowtie]

Originally posted by azk4536:
What do you mean by "signal to the carb"?
"signal to the carb" is basically the way the carb interprets the needs of the engine. While manifold vacuum does a play a part in that the most critical factor is the air speed through the venturi. You can not "always" put a cam with a larger lobe seperation into a carbed application and expect it to perform better. In an EFI motor, you do not rely on this signal and can therefore spread the lobe seperations out even farther without the fueling issues because the computer looks at various factors and can be programmed to make certain interpretations (an example is the late model LS series motors that have cams with 117.5 deg lobe seperation). Also keep in mind that either 112 or 114 are considered fairly wide lobe seperations in a carbed application. It is not uncommon to find performance cams for SB chevy's down in the 106-108 deg range and occasionally even down to 104 deg. Also, contrary to popular belief, wider lobe seperations cams tend to produce more power in the upper rpm ranges as well as in the lower rpm ranges and tend to have a flatter TQ curve; however, narrower lobe seperation cams will make more power in the narrower rpm range they are designed to operate in (and most likely a higher peak number).

[bowtie]

Originally posted by bowtie:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by azk4536:
What do you mean by "signal to the carb"?
"signal to the carb" is basically the way the carb interprets the fuel needs of the engine. While manifold vacuum does a play a part in that the most critical factor is the air speed through the venturi. You can not "always" put a cam with a larger lobe seperation into a carbed application and expect it to perform better. In an EFI motor, you do not rely on this signal and can therefore spread the lobe seperations out even farther without the fueling issues because the computer looks at various factors and can be programmed to make certain interpretations (an example is the late model LS series motors that have cams with 117.5 deg lobe seperation). Also keep in mind that either 112 or 114 are considered fairly wide lobe seperations in a carbed application. It is not uncommon to find performance cams for SB chevy's down in the 106-108 deg range and occasionally even down to 104 deg. Also, contrary to popular belief, wider lobe seperations cams tend to produce more power in the upper rpm ranges as well as in the lower rpm ranges and tend to have a flatter TQ curve; however, narrower lobe seperation cams will make more power in the narrower rpm range they are designed to operate in (and most likely a higher peak number). </div></BLOCKQUOTE>

[cvx16cvx]

Okay okay I have been reading all this. I have the same boat and can not wait to see what engine you end up with. I am just about do the same motor switch. I want a 383 so let me know cause I am doing the same...Chris

[Big Dave]

Me too.
My oldest son and I have been talking about putting a 383 in the diplomat but the old worn out 305 I put in last year still has 160 lbs compression on all 8 cyls.
best so far was 4700 rpm w/ 20p 4blade Mach Magnum Sterndriver 1 person and 1/2 tank of fuel
I asked for a gps for christmas but got a tie instead!!!

[SneakyPete]

CVX,
I have decided I am going to swap the top end and keep the short block in it that it has now. I am hoping I can get away for a few seasons with the targetmaster shortblock. I am going to put in the last cam I posted about, Edelbrock RPM AIR GAP intake, Vortec heads, and keep the MERC carb for now. I will keep my fingers crossed and pray for the best, and take it easy on it. The motor has only about 65 hours on it, so it seems a shame to just convert into lawn ornament duty. I will then save $ for a forged everything short block (prolly a ZZ4) and swap cam, intake, and heads over. If the current shortblock does let go, hopefully it won't take any new parts with it, but as I said earlier, it leads a pretty easy life with an occasional WFO blast for a short period of time.

[SneakyPete]

For you 383 guys looky here:
$6,888 (http://www.enginefactory.com/marine.htm)
and here (I like this one, aluminum heads etc):
$5,995 (http://www.marinepowerservice.com/Engines/GM/detail.cfm?engineID=644&SETmodel=HIGH+PERFORMANCE+383+-+425HP)

[bowtie]

Originally posted by azk4536:
For you 383 guys looky here:
$6,888 (http://www.enginefactory.com/marine.htm)
and here (I like this one, aluminum heads etc):
$5,995 (http://www.marinepowerservice.com/Engines/GM/detail.cfm?engineID=644&SETmodel=HIGH+PERFORMANCE+383+-+425HP)
I would almost be willing to bet that that second 383 motor (the one with the Crane cam) has the exact camshaft i have in my 355 and the one I posted about in the beginning of this post. Also, if I were to purchase a crate motor 383 and did not mind aluminum heads, this is the one I would go with: http://www.sdpc2000.com/catalog/120/products/156334/ZZ3...h-Aluminum-Heads.htm (http://www.sdpc2000.com/catalog/120/products/156334/ZZ383-425-425-HP-383-Small-Block-Crate-Engine-with-Aluminum-Heads.htm)
Notice it has the same HP and Tq numbers as the $5995.00 one you posted but over $1,200.00 less. Of course you would have to finish it out with an intake carb and other items but I think it would still be less. In fact if I could not build my own I would consider that motor for the Suburban. That said since I will build my own I will opt for a better crank, rods, and pistons than in any of these motors and go with some ETEC 170's for the Suburban and stick with the cast Darts for the boat. I have never liked the Hypereutectic pistons that all of these crate motors come with (they do not expand as much as the other piston materials allowing tighter cylinder bores which is good, but they are extremely brittle and if running a fresh water cooled system you should not run the cylinder bores that tight anyway), I also have heard and seen bad things with these low cost imported engine parts, and am slow to jump on the powdered metal rod phenomona. I would stick with some heavy forged pistons (Speed-Pro), a Lunati Sledghammer steel crank, either some Lunati, Crower, or Manley Sportsman grade rods, along with some 3/4 groove Speed-Pro main bearings and either Speed Pro or Clevite rod bearings, and some good old fashioned meticulous machine work. Oh, and I would most likely stick with the exact same cam I am running now but perhaps add some 1.6 rockers to get the lift up around .543/.563.

[SneakyPete]

Good point. The 2nd motor comes with E-Tec 200's, and your has GMPP Fast Burn. I would defintaley save the 1200 and go the GMPP route, and spend the difference on a Bravo. I have read different things in reference to the PM rods, on site listed them as "Forged" Powdered Metal, personally I don't know anything about them.

[SneakyPete]

GMPP 383 for $3500 (http://store.summitracing.com/default.asp?target=partdetail.asp&part=NAL%2D12499106&N=115&autoview=sku)

[SneakyPete]

That is for the short block, just add cam, valvetrain, heads, intake. Maybe this is the route I will go down the road, then again, I have to think of my poor Alpha.

[bowtie]

Originally posted by azk4536:
That is for the short block, just add cam, valvetrain, heads, intake. Maybe this is the route I will go down the road, then again, I have to think of my poor Alpha.
I would just go the crate motor route... There is no way you can get a good set of heads (especially aluminum ones if that is waht you want), a complete roller cam set up, roller rockers and pushrods for $1270.00. Of course if you wanted to go with cast iron heads for fresh water cooling durability issues or are just dead set against using that cam then that might make a difference. Although, it may still be cheaper if you just want a different cam to buy the crate and then swap out the cam (since the crate would still include brand new roller lifters, retainers, spider and roller rockers and pushrods.

[SneakyPete]

What do you all think of Pete Jackson Gear Drives? I have heard different things, such as transmitting of harmonics to the cam etc. The idea of a little whine would be cool, but do you thing it would get real annoying after a while? I don't know if this is considered "rice" by going for "bling factor"...maybe I should also put a "TYPE R" sticker on the boat too. I have never heard how loud the noisy ones are though. Just wondering, but I will most likely save the $120 and buy a double roller.

[vinny p.]

Dont even think about the Gear drive..You are better off with a chain. You know my opinion on crate motors, I am ot going to repeat myself. Be careful with the compression, it is a bit high on all of them. Eagle internal components are made in China. They are not the best and are heavy. Hypereutectic pistons are ok, but they ar far from forged. JE makes about the best out of the box pistons.

Good luck with this build.

[SneakyPete]

Originally posted by vinny p.:

Good luck with this build.

This sounds like it being said with the expectation of disaster http://www.checkmate-boats.com/infopop/emoticons/icon_wink.gif

[boatman4021]

Vinny is right, stay away from the gear drive. Nothing to be gained but ALOT of noise! Hypereutectic pistons while far from being junk, they are not near as strong as forged. Although I have used them in some fairly hot setups, including nitrous, all you need is for one piston to come apart to realize that forged really doesn't cost more. Pay now, or pay later. On the other hand, if it's a low compression, low rpm motor, in the 300 to 350hp range, save your money. boatman

[vinny p.]

No, thats not what I meant. I just meant good luck. It is not the direction I would go or recommend, but that doesnt mean it is wrong. You have to do what is right for you and your budget. When it comes to building an engine, I become over critical. I like to pick each part and put them together myself. I trust nobody to put their hands on it. Call me what you want, but I know how to build an engine. Opposite to what others have said, all engines are not the same.

[boatman4021]

Not disagreeing with you Vinny. It's clear to most people that you know your stuff. We all know(or most of us do) that better is always better. But sometimes overkill. I would not make fun of anyone for using the best parts that money can buy. Was just stating my opinion. Don't get upset with me! It's too dang cold and snowy for me to drive all the way up there to buy you a beer! http://www.checkmate-boats.com/graemlins/thumb.gif boatman

[bowtie]

Just curious how many of these guys have experience with gear drives??? Anyhow, yes it is true that they convey more harmonics to the valvetrain (if you think about it the crankshaft does not turn snmoothly when the engine is running, it somewhat jerks forward everytime a cylinder fires)and this is transmitted more to the cam with a gear drive than a chain which transmits more than a belt. That said, gear drives used to be the choice of serious offshore boat racers due to their durability over chains years ago, but I do not believe that is the case anymore. As for the gear drive sound... I ran one for years in my street car years ago and still have it. Some people knew what it was, some people thought I had a blower (I also ran a tunnel ram), but most just thought I had a bad power steering pump (I did not even have power steering). Of course since then Pete jackson has come out with a quiet drive and a loud drive (there was only one back in the 80's), and I am not sure how they would compare to mine as far as sound is concerned. If it were me, I would stick with a good double roller chain for the boat. Of course I will most likely run a belt on my project car if it ever runs again.

[vinny p.]

boatman,
Dont get upset. It was a general post. Also, I never drink beer or alcohol at all. Never acquired a taste for it. Actually, today was fairly warm around here, in the 40's with 50's coming the next couple of days. You just would have to get past the 2 feet of snow that fell on us this weekend. I hate winter.

[SneakyPete]

Vinny,
Can I reuse my stock pushrods, or should I use he ones Comp recomends (7.8inch)? Also, when I switch springs, can I reuse the retainers, or do I need new ones? If I buy bare heads, can I just buy the valves and install them, or do I need to have them cut first?
BTW
I just read in a magazine, Power and Performance, that Comp Cams recomneds using their LS1 Beehive spings on the Vortec heads, which would allow up to .580 of lift without machine work. The beehive springs are a single spring wound using oval wire, this allows it to fit over the larger stud found on vortec heads, as opposed to the double springs which won't fit over the wide studs and require machining a new pocket to allow fitment. The springs are almost twice as expensive, but they are lighter. I'll post more later when I have the magazine in front of me.

[boatman4021]

Vinny, I'm not upset. All is in fun while we compare notes. I'll let people make there own decisions and let it go at that. I can't get mad at anyone on this site, everyone is just trying to help each other. As for the beer, good call! While I spent many years taste testing http://checkmate-boats.com/graemlins/lol.gif, I don't consume anymore either. Maybe a cup of coffee? By the way, we got over a foot of snow right here. It sucks! Come on spring! boatman

[vinny p.]

Boatman,
No problems here either.

AZK,
You may be able to use your original pushrods, you will have to check your rocker arm to vakve tip wear pattern to be sure. If you are not sure how to do this, Comp Cams has the procedure listed on their site. You most likely CANT use those retainers. You can check with the Comp, but I am almost 100% certain they wont work. While I have not tried them myself yet, I have heard of good things with BeeHive springs. If you are getting new retainers anyway, get ones that use 10* locks. Those are much better than 7* and cost pennies more. If possible, opt for titanium retainers or at the very least steel. New valves will have to be cut along with the heads. You should not use a automotive head valve job anyway. Marine engines require a wider seat cut to allow the seat and valve to cool better.

[happy]

push rods are alway the last sequence to a rolling assembly.. the lower end engines never see but one check.. (if lucky), the higher end engines (say 5oohp+) each lifter gets checked on every valve.. and more anal afterwords..(hp wise)..

[SneakyPete]

How can I figure out the compression ratio once I get the old heads off? I have no idea what kind of pistons are in the block right now, flat tops, dished (doubt it), pistons with valve pockets etc.

[vinny p.]

This link may help..

http://www.hotrod.com/techarticles/54258/

[SneakyPete]

Do you think I could get away with using my stock carb for now, or should I step up to a 750cfm Edelbrock Marine Performer? BTW, just started ordering stuff, got the heads from Jegs for $499.98!!

[vinny p.]

what carb do you have?

[SneakyPete]

Ill have to check the carb. I got my heads the other day, they are pretty dirty from machine oil and metal shavings, how should I clean them up, soap and water, brake cleaner?