I have an '86 IROC that I put a '78 350 truck motor in. It's bored 30 over, with a small oversized cam, Edelbrock Performer intake, 650cfm Edelbrock carb, but only 305 heads.

I don't have the horsepower, are the 305 heads what is hurting me?

 

For starters yeah, but are you running stock manifolds as well. Also, that is a truck motor so most likely it wasn't built for racing. What kind of gears do you have in the car as well, mine came with the crappy 2:73s.

 

big time

 

wouldn't a truck also have lower compression? just a thought

 

I've got 3:73 gears with a 5 speed. I do have the stock manifold. I have a set of '69 heads (194's) to put on, if it will make much difference. The motor has flattop pistons.

I don't really want a "race" car, just more power of the line. Top end is real good.

 

Yeah, I think trucks do have lower compression, but he has different heads, doesn't that affect the compression.

 

but.. even a stock 350 will normally make 280-290hp (when using 1.94and 1.5inch valves). A stock 305 head had 1.74 and 1.5 i think. the ho305 were 1.84 but that is as big as they got. It can probably be made to have good torque upto about 4500 but thats going to be about it. Make sure you got good advance curve and the secondaries are opening all the way. It needs at least 2 1/4inch exhaust pipes.

 

yeah, it'll bring it up a bit but if i'm correct the trucks had more than a few points lower compression, somewhere around 9ish?

anyways, the valves in the 305 are hurting performance, and the smaller combustion chambers in the heads will hurt flow, i'd guess..

probably a few factors involved there

 

rocman - do you want desktop dyno to see what the difference would be? let me know.

 

Wouldn't mind desktop dyno, but I don't have all my exact info. Plus, this is all new to me.

The car had a 283 with doouble hump 194's and flattop pistons. It had a lot more power then, but blew it and let my step-son have the heads.

 

Wouldn't the 58cc chambers and flat tops give compresion over 10:1? That should help in the lower end power. Try to find the cam specs. They heads may be giving out of breath before the cam gets going, just a mismatch of parts.

 

I IMed you concernting Desktop Dyno, just wanted to make sure you were accepting IM's and check it out. Thanks

 

Don't have IM yet.

What size cam will do the most good if I put the bigger heads on. I have heard the 5speed isn't very strong, don't want to rip anything.