Fresh air in the bilge to make more power.

[bigsbetter]

Rob, You and I have the same boats. My engine hatch is raised up with a 2x4 frame wraped in red vinyl to clear the super charger/air cleaner set-up. The 2x4 frame is excatly the same size as the rectangle swim plateform. If I cut out and installed some vents on the rear of that frame, would that do the same as a scoop facing the rear? The hatch has 3 hinges, maybe put 2 vents, 1 on each side of the center hinge? anyway.....just think'n.....

 

[Big Red]

I guess my boat is set up a bit different. But what scoop are you talking about turining around backwards.

 

[bigsbetter]

The 'scoop' would be an aftermarket custom "hood scoop" either facing forward or rearward. But some of us don't want to cut a hole in out rear decks, so I'm trying to figure something else out, although the big scoop channeling fresh outside air right to the flame arrestor would be ultimatly the best for the engine.

 

[Big Red]

I would like a scoop myself, but I will not give up my sun-pad for it. I have never seen a scoop mounted backwards that would defeat the whole purpose of the hole ram air effect with fresh air. A lot of speed boats around here have a scoop but none are mounted backwards

 

[ezstriper]

I think it would work nice to build up your sun deck, keeping your sunpads, with maybe a 3-4 opening in the rear, I have seen some factory biats built that way, just a thought. Also i am confused about what you were saying about the the 2x4 frame work ? not sure what you mean there ?? Rob

 

[ezstriper]

this is how I did mine...now I had the scoop laying around and needed to re-do the pad anyway...if I can get this pic thing to work..Rob

<a href="http://s227.photobucket.com/albums/dd69/ezstriper/?action=view&current=100_2360.jpg" target

 

[bigsbetter]

Rob, my entire swim plateform/engine hatch is raised the height of a 2x4 which is 3 1/2" to clear the air cleaner. Letas say the swim deck is 4 foot by 6 foot. My 2x4 frame is also 4foot by 6 foot. I took the swim deck off and mounted the 2x4 frame to the boat using lag bolts, then mounted my hinges for the swim deck to the 2x4 frame. It looks good and nobody notices it untill I explain it to them.

 

[ezstriper]

Ok, I got you now...wondered how the carb cleared...hoping to have my puley deal fixed this week, should get another in today...Rob

 

[winter]

I have never seen a scoop mounted backwards that would defeat the whole purpose of the hole ram air effect with fresh air.

What needs to be understood is, you can face a scoop forward and assume you are ramming air into the engine bay. But if there is no equal outlet for the air to escape, air won't be rammed in. The only way a forward facing scoop works without addressing the exhaust side of the engine bay is to seal the rammed air to the flame arrestor/filter.
FWIW, there is usually allot more air inlets than outlets on an I/O. I have two large areas along side the rear seat and one side vent facing forward. The only outlet is the starboard side vent, facing rearward.

 

[Big Red]

What needs to be understood is, you can face a scoop forward and assume you are ramming air into the engine bay. But if there is no equal outlet for the air to escape, air won't be rammed in. The only way a forward facing scoop works without addressing the exhaust side of the engine bay is to seal the rammed air to the flame arrestor/filter.
FWIW, there is usually allot more air inlets than outlets on an I/O. I have two large areas along side the rear seat and one side vent facing forward. The only outlet is the starboard side vent, facing rearward.

I know how a scoop works I have been on the drag strip for years. Simple fix stick the air cleaner threw the sun pad.

 

[ezstriper]

yes, the way to do this is to seal off the base of the flame arrester so the engine only breathes the outside air, which can be 50 deg or so diff in temp...and will make a big differnce..even more so with a forced induction system...Rob

 

[winter]

I know how a scoop works I have been on the drag strip for years. Simple fix stick the air cleaner threw the sun pad.

...and make sure the 1/2 naked chickies don't skun their shins on it But... since you seemingly enjoy classic muscle cars much like myself, you'll surely know that a scoop does not have to face frontwards to force air into an engine, or a carb. A classic, but certainly not unique example of of this was a first gen camaro with the Z-28 style cowl induction hood. Same for a similar Chevelle. Both took advantage of the pressure difference between the lower end of the windshield and the air flowing over the top of the car. Boats OTOH are a bit different in nature, as far as air flow and where engine bay air is exhausted, but the same rules of physics still apply.

 

[Big Red]

A flapper hood or a a non flapper hood makes no difference on a 1970 SS 454 Chevelle. The only speed gain I got was taking the hole breather assembly off. I gainded at the drag strip 3/10th's faster running no type of breather. All the gm cowl hoods and flappers are for looks only no speed gains. I am a mopar man I have some Chevy products only for money reasons and resale. Mopars and Fords never used a backwards scoop

 

[winter]

Dunno Red, that goes against everything i have heard and learned over the years. Admittedly, drawing air from the windshield end of the hood is not nearly as effective as ramming it in from the front. However, the intent with cowl induction was to draw cool air into the carb itself. That's why there is/was typically a rubber seal downwind of the opening to direct the fresh cool air into the carb while keeping the hot air from the radiator from entering. That trick alone will, under all circumstances, will provide a better, denser air/fuel charge which will lead to more HP. The effect of actually ramming air into a carb has its own benefit, but that's in conjunction with making sure the air is cooler than what the radiator is thowing off.
Now the efficiency of Chevys cowl induction systems have been debated as being all but worthless, but still, it's theory is proven. Nascar for instance, draws air from the windshield area.

 

[dogschool]

very nice ride!

 

[Big Red]

Just what I have found that the factory set up restricted to much air flow. I agree 100% on cooler denser air. On a factory cowl set up the carb had to work to hard to pull the air to it. When ran without the assembly the card had air all around it and did not have to pull it from anywhere. Now my 3/10ths faster come from 1/8 mile runs on the track. As for as Nascar goes running at high speeds the hole time the air is already flowing unlike a dead stop launch at a drag strip.

 

[winter]

Good point Red. 3/10ths in the eight is allot. but you have to admite, it sure as H3ll feels like you are going faster when that cowl induction flap flips up right in front of your eyes!

 

[ezstriper]

the reason you picked up by removing the outside air source ment your engine was jetted to lean...by removing the outside air you richened it up, with jetting dialed in with out air you will make more power....if you can benifit from it...tires....Rob

 

[ezstriper]

as far as scoop facing front or rear, forward will work better, but only if the opening is 5-6 above the hood level, low scoops work better rear facing, have seen the wind tunnel test...the air rolls right over a front facing low scoop, rolls down the windshield and impacts the back of the hood, GM originally di the rear opening to vent out hot air, but then found the ram effect in later wind tunnel test...Rob

 

[hotdaddy27]

Thats why I love this site.....

not only do I learn more about boats than I can handle, but I also learn about cool stuff like the theory/testing behind air ram/induction.

Not to mention I get to see pics of cool cars (owned by real people).