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Discussion Starter · #1 ·
hear are the details on my engine:

longblock:

HO 302
E-303 cam
AFR185 heads
comp cams chromolly 1.6 rockers
hardened pushrods
hydraulic lifters

induction:

edelbrock f28 dual 4 barel intake manifold
2 edelbrock 500cfm carburators.

exhaust:

1.5" shorty headers
custom J pipes
FF5 sidepipes

electrical:

msd6 ignition
msd billit distributor

hears the story:
I put this package together a few years ago. at first I was very happy with it, it started right up strait out of the box and has never had any problems running or starting. it sounds good, never even comes close to overheating and gets 20 miles to the gallon. the engine has always run without any noticeable problem, but I have always felt that it was not really making good power. it took a bit of playing with the jets to get the AF right, but I finally got it to a point that felt good. So last week after 3000miles I took it down to a dyno tuner in ventura for a dyno day that stangfreaks.com was putting on. in the end the car put down 210 rwhp at 5800 rpm with a verry flat torque curve (curtasy of the E-cam I think). this was on a superflow dyno at sea levle 55 dagrees ferenheight. the AF was right at 12.5 threwought the RPM range. we tried advancing the timing a few dagrees but the engine didn't run as well so we put it back where it was. I am relatively convinced that I am limited by my somewhat unconventional induction setup and I was wondering what you guys think, has anybody made decient power with this induction setup? what would be a good carb/intake setup for my system to make better power if I got rid of the intake?
 

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1,326 Posts
Layne I may be wrong and others will chime in - but I think you have waaay too much head on that little motor - might be killing your compression ratio and/or flow and velocity rates - I'm thinking 165's might be better.
I would hazard to guess you may be over carbed too - I run a 600 Holley on my E303 cammed 302 though 12.5 sounds about right so maybe it's a compression issue - with those bigger heads you may be down around 8 to one compression.

Try posting in the Ask an Expert section.

Scott
 

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Master "Gear Head"
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434 Posts
The AFR 185's are a little big for the motor for sure. It is big in the intake runner volume not the combustion chamber size, so your compression ratio is not affected by the 185's over say the 165's. The combustion size of the the AFRs is smaller than stock heads so the CR should be higher than stock 9:1 CR if the pistons are installed at or near stock height. The oversized 185cc intake runner will make the velocity lazy at lower RPMs but should not affect the upper RPMs and should make for the possibility of a higher max HP. Your AFR is good at 12.5 at WOT. You might look at timing (did you degree the cam to make sure it is not installed advanced or retarded?) and possibly some mismatched gaskets creating some bad port matching. Possibly an exhaust back pressure issue.

I have seen dyno results that show the dual quad setup is down on max HP compared to a single 4bbl intake/carb setup but the dual quad setup produced more torque.
 

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Indeed, the 185's are a little big. To take advantage of them, you need more RPM and better breathing.

I don't see airflow capacity being a problem with two 500cfm carbs, but you might have a severe port mismatch with that intake as was mentioned above. This would cause turbulence and kill airflow and power, especially if the mismatch is at the top of the ports.

Also, just because it has a total of 1000cfm carb flow on it does not mean the intake manifold flows that well.

I would suggest:
1. A dual pattern cam with more exhaust duration by about 6 degrees.
2. Try a Performer RPM air gap intake with a one inch phenolic spacer ( 4 hole ) and a 650 Holley or 570cfm Demon.
 

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Oh Yeah - Don is correct again - that intake set up on a 347 would be a killer!!

Scott
 

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I disagree ! I use dart sr's(200cc intake port, and ported) and a small Lunati cam on a 9.2:1 306. This made enough power to push a full weight + roll cage 89 GT hatch to 12.30's The car weighed 3250 lbs. This is with a GT40 intake. You didn't mention compression ratio or engine mileage/ condition .I'm guessing you have the the 8.8:1 compression that with your e cam should net 280 or so at the flywheel.The e cam is very small by todays standards your avg hoppd up 302 is probably using something like a 550 or more lift cam. The E is for emission control cars . A good custom cam for ground on a 110* centerline with 550-565 lift might net as much as 75 hp .It is possible to make 350-375 fwhp with the right cam . Call some cam manufacturers tell them your combo dual carb and EFI are way different camshaft wise. I don't think youll achieve much by swapping intakes .Mill a little off the heads to get the compression to at least 9.2:1 ... 10:1 + will run on pump premium but I don't know how much you can mill off the heads. I'd start with with .015 Bob
 

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Not sure how much gain would be had if just changing carb and intake other then throttle responce and maybe a little better milage. Think you are under camed for that intake,head combo espeacally at 5800 rpm's.
 

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Discussion Starter · #9 ·
I know that 185s are big for a 302, but I got them with the antiscipation of someday putting in a 331 or 347 stroker, but I am not ready to go that far yet. the engine only has 3000 miles on it, it was new when I got the short block.
I don't think it is a port missmatch problem because I port matched both the exhaust and the intake. the heads have a 58cc combustion chamber. I can't put a much bigger cam in the car without notching the pistons because the valves only barly clear right now as it is, but if the problem is that I have the absolutely wrong cam in the car then that might be what I have to do.

I did not dagree the cam(how do you do that?)
I did check appropriate valve opperation on every cylinder and confirmed appropriate timing order when I installed the rocker arms. again as stated before the car runs quite smoothly as it is, but if I try to advance the timing much more it stops running smoothly.
 

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Layne good your engine is fresh and sealed up well. You need to keep in mind all the engine components need to work together and complement each other. As is your close to that with having the better breathing/flowing heads and carb manifold but it stops there. Not having a cam that will allow more air fuel into the motor it can't make better use of the other parts. Maybe degree your cam to see how much P to V clearence is left and go with a larger cam if possible. Other option would select the cam needed for your parts combo and do the needed machineing to the pistons. Right now your not taking advantage of the motor with that cam used. Larger cam or smaller induction/heads package.
 
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