Well first i will start with what has been done to my motor, its a 302 that has 9:1 compression, ported heads with over sized valves(1.94 intake and 1.60 exhaust). Headers, comp cams extreme energy camshaft with 512 lift and 280 duration. A holley 670 cfm carb and a edelbrock performer intake. the problem that i have been having is that the car gets a awsome jump off the line but then falls flat on its face, the car also doesnt seem to want to rev above 4,000 rpms. Its not a monster combo, but its a good high performance street combo that really isnt proving itself. I am think that the Edelbrock performer(yeah thats right, performer, not performer RPM or airgap, just the plain old performer intake) isnt doing me any good and maybe even taking away power, after all are the ported heads and the cam even benefiting from that little intake. Also the car has a built c4 with a manual/automatic valve body and a posi 3.55 rear. Soemthing just doesnt seem right, the car shoudl eb able to rev up to 6,000 with out a problem. What are some of your suggestions? Do you think its the intake?
matt

 

hey, I have the edelbrock performer RPM airgap in my 289 with slight mods (in sig) and it revs to about 5500 easy. i highly recommend it. good luck!

 

My 67' has the performer intake and matching 600cfm carb. It runs and drives great. It makes good torque and power from idle to about 5500 rpms. It may be a bottle neck in your combo,but I doubt its the reason its only reving to 4,000 rpms. When you say it wont rev past 4,000 do you mean like physically it wont go any higher? or do you mean it just sounds like its straining?

 

No, i can get it past 4,000 ut it just sounds like its straining and it doenst pull nearly as hard. I have the rev limiter set at 6,000, so thats not the issue. It just seems more like the motor runs out of air.
Matt

 

I would start with fuel delivery issues. I'm not sure what it feels like when it does it but I had a fuel pump go bad and it did a lot of what you described.
A fuel pressure gauge is a good way to check. Mine would go 6lbs then I would stomp on it and 5.5 5 4.5 (SHIFT 2ND gear) 3 1 0lbs then it would fall on its face. new fuel pump fixed the problem.

Gun

 

Sounds like the fuel side of the equation to me too.

 

I will definetly look into the fuel pump issue, after all it is just a new stock fuel pump. Do you think that the carb could also be an issue, I cant really say that i have ever really felt the secondaries ever kick in.
matt

 

+1 with good pull through 5500 with the performer and 600cfm. Pulls good thru 6000 since upgraded to aluminum heads.

 

i'd certainly replace the pump with a better unit, they are cheap and easy to install. also do you know what your total degrees of timing is? another thing would be to put a lighter spring in your secondaries, and let them open up quicker. (i didnt even know holley made a 670 vacuum secondaries but they have a lot of oddball sized carbs)

no, the intake isnt your problem, but yes with your mods a RPM airgap would be a much better choice to unleash some more of that HP

 

Have you done any mods to the ignition? are you still running points? whether its the cause of your problem or not i would upgrade the ignition. msd box, petronix, something.