deadlydecapod

Hi, guys'

I'm from across the pond but still have the same problems. I've just had the heads changed on my 1980 L48 Vette and I seem to have a flat spot with the 'pedal to the metal' scenario. The car is factory standard except with an Edelbrock cam, Edelbrock heads a rebuilt Rochester and all the emissions gubbins removed and a pair of stainless steel pipes underneath.

The compression has gone up to 10:1 apparently but there is a definite pause when you floor the pedal. It then roars into life and everything is hunky dory.

My other question is just how much hp gain should I expect from the above mods. Factory standard was 190 so now where do I stand ?? I reckon about 275 ?????? It doesn't half sound good though. Grrrrrrrrr.

standup

..........it might help to post the specs on the cam and heads (chamber size intake runner), trans & gearing.....

Is it a stock intake manifold and stock exhaust manifolds????????

275hp doesn't sound off the mark if it's a mild cam/heads........

deadlydecapod

Right, well I got back eventually. Cam is an Edelbrock performer, intake and exhaust manifolds are stock. Transmission is automatic and rear axle ratio is a tall one but I can't remember the ratio. Chamber volume is 64c.c on the RPM heads.

Does that help at all ?

The consensus over here is that the accelerator pump needs adjusting but if that is the case what figures do I take as relevant. Surely with the changes I've made the stock figures won't make sense.

gerry72

More so than you think. The Performer cam is pretty mild and is intended to improve the cruise rpm torque range with nothing to offer on the top end. The heads are contributing more than the cam but not by a lot and has little affect on the upper rpm ranges without a corresponding cam. If you had done a baseline dyno run you'd probably find 20 and maybe as much as 30 more horsepower to the rear wheels depending on your tuneup. Most of the horsepower is locked away in the stock exhaust manifolds and pipes. It's pretty hard to come up with a number, though. Horsepower is a mathematical manipulation of torque and to increase horsepower you need to improve the measured torque and/or stretch or raise the rpm band at which your engine's torque curve/peak occurs. But the reality is that if your modifications make you happy then the measured horsepower number is irrelevant.

About your flat spot...was it there before the modifications?

Boofers

One thing it could be, which is a quick thing to check, is your carb secondary airflap spring tension. If this spring tension is too low when you open the secondary throttle plates the engine will bog because of a sudden inrush of air.

Do a forum search the procedure has been posted numerous times.

Pauld

Welcome to the forum Tony, Who did the work for you and may I ask how much it cost you. I live in Kent and I am always toying with the idea of similar mods to my '81. Also post some pics of your car if you have any.