"Spare" 454 Build-up... 96 L29 Vortec 7400 to Marine Motor

[Gimme Fuel]

Ok, since I am STILL waiting on my block to be done for the 540 I couldn't pass down a smoking deal on a running take out 96 L29 Vortec 7400 truck motor that I got the bright idea (only a year after I was suggested to do this....I never listen...haha) to build a spare motor so I will not spend another season high and dry.

Meet the $450 wonder motor! Complete with clutch fan and A/C Compressor:





She is on the dirty side and looks like she suffered from leaky valve cover gaskets/oil cooler lines. Oil was clean and she had decent compression when I turned it over with socket, so home she came.

Now, here is the breakdown of what we have to work with:
-Block is Gen 6 454 with Hyd. Roller Cam
-GM cast crank
-3/8 dimple rods
-Cast dished pistons
-Heads are L29 (#279 castings) which are small (100 cc) closed chamber "fast burn" style heads, large ovals
-Tuned-Port fuel injection manifold
-partial wire harness (guy cut it instead of unplugging for removal) and all the sensors/coil/distributor

THE PLAN:
Since this is going to be a scab/budget spare motor build, I am restraining myself not to get carried away, yet I want more than the 310 HP the marine version of this engine makes. Now, I have done some research and people will say it has awesome potential and others say every part on it is scrap. There have been many builds on OSO of successful "330 on roids" so that is what we will go with on here. I will also keep a tally of what it is costing me.....cause I'm curious how cheaply I can do it. Goal is to keep it around/under $1500 using my account at local NAPA for most items. The goal is somewhere around 450-500 hp which is very well in the realm of possibilities.

SHORT BLOCK: will get rebuilt with fresh bearings, new rings, and a ball hone cylinder finish. Use stock crank, stock rods, and stock pistons. I will change out the rod bolts to ARP however because that is the weak link with these particular smaller rods.

HEADS: we will retain the L29 heads for the build. With some clean up/mild porting they will support our needs. Plus with the pistons being dished to account for the 100 cc chamber, swapping heads to 088 rectangles would kill the compression ratio which I believe is around 9:1 stock. These are large oval ports and throw out similar flow bench results to the famed 781 ovals. The advantage with these is the "fast burn" style chamber which can help the combustion significantly but also be detrimental if you don't pay attention. It takes very little spark advance at WOT for these to work properly (30-32 deg) and the protrusion can cause detonation because it stores heat. I have seen several street builds using these heads and the HP goal here is obtainable and on the upper limits of their capabilities which is fine. I need to dosassemble and inspect the valves on these heads. Some say truck motors came equipped with Inconel exhausts. If so, big win to the budget provided they are in good shape. I will need to change springs to run the cam however. The stock springs have a very mild bind height so they need to go. I will be using a set of 1.7 ratio EPWI roller rockers I scored for a mere $90. They look purdy.


INTAKE: the stock tuned-port intake is not going to allow close to our goal HP. Luckily Edelbrock just released the large oval port version of the Pro Flo XT manifold which is pictured below. It will allow the use of the efi sensors/throttle body of the era without too much custom fab work. This will also be the most expensive part planned in this build (whopping $370 plus fuel rails) but will match well with these heads to meet our goal. I will procure a cheap 105mm LS1 throttle body for use on this.

CAM: I will use the Bob Madera ground for my old 540 MPI setup. It is a very healthy stick that should do quite well compensating for the limited head flow just like it was designed to do on the MPI intake. Besides, it is on my shelf. Do I need a better reason than that? It makes some good RPM so I might limit it a bit to keep that slightly wimpy bottom end happy. From what I read 5500 should be fine though.


FUEL/EFI SYSTEM: I will use the same Aeromotive A100 fuel pump/regulator and EFI controller for both engines. Each engine will have it's own wiring harness meaning I will need to just switch the Holley HP series ECU between them and load separate mapping. This is a self-tuning ECU by the way so that is why I like the idea of using it. It has been doing awesome in the marine world according to Bob.

Now, I realize this is just the tip of the Iceberg here, but I will show what will be changed to turn a truck engine into a marine engine. Although they are similar, there are several important things that need to be addressed. Stay tuned sports fans. This is what I will be doing while the 540 build is at a stalemate.

Last night I got all of those heavy truck parts off of the front (anybody need any of them? Going cheap). I also got my first look inside. The only issues I have found so far is a broken exhaust manifold stud, a ready to fail harmonic balancer, very rusty oil pan, and some mild rust in the exhaust ports from sitting. Nothing out of the ordinary in other words. Give me a few more days and I will have the intake and oil pan removed to see fully what we have.


Other side looked the same. Nothing obvious. That was about the point of the evening where the camera phone died.


Should be good for 6000 rpm right?

 

[atc250r]

Love me a budget build.

 

[Rcenter1]

I thought about this too. I think you can make a good back up for that money. On a side note I had a salt water harmonic balancer tear apart on my 1 st boat. Cost me a front main seal. be interested in the HP you get out of her.

What exactly is the difference between a regular block and a magnum? How do they get another 60 hp out of those? Do you have to have a certain block to begins with or is it all in the internals cam and heads etc....?

 

[Gimme Fuel]

The true "magnums" had rectangle port heads and all forged internals with the 7/16 dimple rods. Carbed versions were 365 hp and mpi mags were 385 hp. There were a few years in late 80s where they called the 330 hp 454 mags. Those were basically what im starting out with here and what people get into arguments whether or not they are worth building. Cast internals and oval ports. As far as the blocks themselves go, those are the same depending on hp version of 454. The difference depending on year was gen 4,5,6. Gen 6 is most recent from 96 up (hyd roller cam, one piece rear main seal). Gen 5 was i think 87-95 (one piece rear main seal, hyd flat tappet), and gen/mk 4 were 86 older (two piece rear main seal, flat tappet).

 

[Rcenter1]

The true "magnums" had rectangle port heads and all forged internals with the 7/16 dimple rods. Carbed versions were 365 hp and mpi mags were 385 hp. There were a few years in late 80s where they called the 330 hp 454 mags. Those were basically what im starting out with here and what people get into arguments whether or not they are worth building. Cast internals and oval ports. As far as the blocks themselves go, those are the same depending on hp version of 454. The difference depending on year was gen 4,5,6. Gen 6 is most recent from 96 up (hyd roller cam, one piece rear main seal). Gen 5 was i think 87-95 (one piece rear main seal, hyd flat tappet), and gen/mk 4 were 86 older (two piece rear main seal, flat tappet).

So you are using the intake and cam to gain the performance? By doing this you are hoping the non forged crank and smaller rods hold up? Did the pistons you listed come in the engine or did you have them on your shelf?

 

[Gimme Fuel]

Exactly. There have been many with this bottom end built around 500 hp for marine use, even a few with blowers on top. If the tuning is slightly conservative meaning a little fat (or efi to control/monitor) and not wicked timing curves they live happily. I will be using the stock pistons, stock heads, stock crank. Bottom end just gets new rings bearings gaskets. Keep in mind i will also be running mostly dry performance manifolds so that helps a bit too. The intake and cam are where i am trying to gain the power. The factory cam from these 310/330 hp motors are very anemic. The cam that is going in may be a little on the big side (many have had good luck with zz502 cam which is a bit smaller). Basically im trying to see what this motor that so many big budget guys claim is junk. From what I gather, it is a good base for 500 hp and under still which makes a perfect spare. I will be taking the necessary precautions to fix a couple easy weak points like rod bolts.

 

[yellowfiero88]

Swap accessories and bolt in. Leave it alone and don't beat the fuk out of it. That way you might be running for 2014!!

 

[Problem Child]

That will be a great budget build and a pretty good runner. Im thinking put the back up motor in first so you will be on the water enjoying that 253 asap. If you can use a hand putting it in let me know. Anything to get you on the water lol. Cumberland or bust 2014!!!!!!!!!

 

[ezstriper]

what are you going to use for a computer ? not sure I would spend that kind of $$ on that intake unless you are going to run that on the 540, not sure that cam is going to work well with that loss in cu in. just a thought...

 

[Gimme Fuel]

Swap accessories and bolt in. Leave it alone and don't beat the fuk out of it. That way you might be running for 2014!!

Come on, have you ever known me to do any of that? Haha!

I thought I was pretty much leaving it alone by only changing intake, cam, and springs along with bearings/gaskets!

 

[Gimme Fuel]

Ok, I did some more tearing down last night. Had a couple surprises, one being I found flat-top pistons when I was expecting to see dished according to what I have read. That would make this a 9.4:1 CR engine roughly. There was a motor designated L21 that looked identical but received forged crank and pistons along with conservative tuning for use in medium duty and motor home chassis. I'm not exactly sure if that is what I ended up with. Once I pull pistons I will be able to tell if they were forged or cast.

The only bad thing I uncovered last night was a bent #1 exhaust pushrod and a lot of hardened sludge in lifter valley (must have run Pennzoil....haha). The water jackets/passages have a bunch of rusty sludge/scale from sitting but it looks like the engine had never been opened. Head gaskets were in good shape and all head bolts were tight. Cylinders were pretty clean other than some dust that got down through intake. I was told it had been sitting for two years since it was pulled out running. Sounds legit.

The cylinders are worn but the original cross hatch of the hone is still visible and there was no rust in them. So far, I think I did darn good for what I paid. Next step is to flip it over and pull the pan. Oh boy!

Here is inside of Tune Port intake....sooo many long air passages. Good for torque...and thats about it:

Upper Plenum:


Intake gaskets looked good. Here is pic of large oval intake runners:


Here is the lifter valley. You can see some chunks of that sludge sitting on the spider plate. There was several large chunks stuck above lifters and behind pushrods also:


Here is the bent pushrod:


Now ready to pull the heads:


Cam looks worn (for a roller) but good overall. The lifters were a bit snug as some had some early stages of rust:


Here is what she looked like when I pulled the first head. Yucky water passages!:


Here is what the combustion chamber looks like with these "fast burn" vortec heads. Looks like it was burning nicely though. Notice the "fast burn" protrusion and 100cc chamber size:



Here are the exhaust ports, supposedly these are the best flowing exhaust runners GM ever made on an oval bbc head:

A wee bit rusty, should clean up though:


The pistons are not set with a TDC below the deck surface either. They are close to even:


Here you can see some of the original honing in the cylinders:

 

[Gimme Fuel]

what are you going to use for a computer ? not sure I would spend that kind of $$ on that intake unless you are going to run that on the 540, not sure that cam is going to work well with that loss in cu in. just a thought...

Yea I thought about that. The ZZ502 cam seems to be a popular swap into this motor with pretty good results. High 400's for HP and torque in mid to high 500's seems to be the norm with intake/carb setup. From what I have read, the tuned port intake limits things severely when you try to use it. I have talked to Bob Madera a bit about this and he didn't have any reservations to be using this cam with a 454. I will talk to him more in depth about it though when we talk about the new cam for the 540.

The intake on my 540 is a very large dominator flange single plane rectangle port intake. Basically my choices were spend money on a set of 088 heads and run my MPI setup or use the Edelbrock intake with the existing oval heads. The cost appears quite similar so I chose to just go with the Edelbrock intake. My PMI setup has been hogged out so much I think with the lower cubes, port velocities will be pretty slow for making good low end torque. These oval vortec heads supposedly make great torque and have quite high port velocities on the 454 from what I read. Of course where did I read it all? On the internet, so it must be true right? haha

What thoughts do you have on this reasoning Rob?

I will be using the same Holley HP ecu that I will also use on the 540. This should work fine seeing as I can only run one at a time. I will have a separate wire harness for each motor to simplify things though seeing as they will be running different ignition setups. I have my one set of manifolds with O2 sensors that will swap over also for using that ECM. The computer is the other reason I steered away from going back to the MPI route. I don't like the idea of not being able to easily tune the engine like with the very limited MEFI1 controller that I have on the shelf.

 

[Kurtster]

Meet the $450 wonder motor!
THE PLAN:
I am restraining myself not to get carried away

Ya sure.......

Finally an engine build thread to follow ----- gonna be fun to watch

"Getter done Ron"

 

[RNGRDVE]

How many miles are on that engine? Spark plugs are the originals.

 

[Gimme Fuel]

Meet the $450 wonder motor!
THE PLAN:
I am restraining myself not to get carried away

Ya sure.......

Finally an engine build thread to follow ----- gonna be fun to watch

"Getter done Ron"

Haha....yea, I don't know when to stop. Bad habit of mine I guess Like I said, "try" to restrain myself...haha. Last motor I attempted got crazy as you all know. Hoping this will be the one I put little thought into, mostly stock parts, runs better than it should, and I can't kill. One can dream right?

How many miles are on that engine? Spark plugs are the originals.

Guy I bought it from said around 200k miles. Engine looks real good for that. Supposedly came out of a rusted out plow truck he got for free that his neighbor was gonna just drive to scrap yard. Guy I bought it from was a self employed mechanic in slow times and needed cash. Has been sitting in his garage for two years. He was going to put it into his '88 chevy pickup to replace the carb 454 in it. Outside of block is real rusty and oil pan is almost shot confirming plow truck story.

 

[RNGRDVE]

200k and never tuned up. I would inspect carefully as maintenance must not have bee high on the list.

 

[Gimme Fuel]

200k and never tuned up. I would inspect carefully as maintenance must not have bee high on the list.

Naw, I figured I would just bolt the heads back on and go! I thought you didn't have to tune up them thar new-fangled compooper carboobators no mores?

Don't worry, it is getting a full inspection/refresh. Bearings, gaskets, seals, springs

 

[RNGRDVE]

Naw, I figured I would just bolt the heads back on and go! I thought you didn't have to tune up them thar new-fangled compooper carboobators no mores?

With how well your last engine build went you never know.

 

[Gimme Fuel]

With how well your last engine build went you never know.

Only thing wrong with that build was azzhole who installed the oil pump pickup tube and the same azzwipe running the throttle half drunk who didn't believe his gauges.

 

[slingblade]

Swap accessories and bolt in. Leave it alone and don't beat the fuk out of it. That way you might be running for 2014!!

I got a 75 shot of NOS .That would put it in the hp range for cheap.pressure wash the oil off it and go!!
if you require machine work will It go in front of the 540 or after. I would look for a new machine shop and divert my $ for the 540. If done right you should not need a backup motor .