Scottd

Ive got a 72 big block with stock pistons and heads. (Mild cam, upgraded intake, carb and exhaust) I know the low, smog controlled compression ratio is what KILLS the performance on this engine. I want to add new heads but I DONT want to mess with pistons. I know Edelbrock makes a 94CC head. Will the lower chamber size increase compression enough to warrant to 2K price tag? Are there any other options?

Super6

Haven't seen 94cc Edelbrocks. I have the 100cc "High Compression" oval ports.

Have you tried a compression ratio calculator? Enter all your info and it figures out the static compression ratio. Then re-do it with the new info from the heads and compare the 2. Then do a search on the effect of a compression ratio change between 8.5 and 9.5 to get an idea. You're not going to see a 10% change. If you did get the heads, I would suggest that you contact Chris Straub for a cam recommendation. He will get the most out of the potential that you have.

Les

I have the same Edelbrock heads and that's the correct chamber size. Do you have the specifics on your pistons? If the engine has been gone through since it left the factory you'll want to know exactly what you have. That could be important info since you'll lose some valve to piston clearance with smaller chambers. I'm not trying to discourage you because the Edel. heads will pick up power nicely due to superior flow anyway, and crisper throttle response due to increased compression would just be a bonus. Do you know the specs on your cam?

Scottd

All I know for sure is the engine is .030 over, and the cam is aftermarket. I dont have as much a build sheet from the previous owner as I do a receipt for the rebuild. So I assume Ive got stock replacement pistons (426NP-40) and the cam spec are 222/235 .500 .505/115 LC. I cant find much on a 'stock cam' so I dont know what benefits the above is giving me.

zwede

100cc Edelbrock heads will help, but not be enough. I have a '71 LS-5 with those Edelbrock heads. With the block decked to 0.005" and 10cc dome pistons I'm at 10.15:1. Factory pistons were flattops.

When I had my engine done it also turned out that a PO had installed some truck pistons with a different pin height that dropped the pistons down about 0.040". And to top it off, the decks were crooked from the factory. One end was 0.020" higher than the other end. The worst piston was about 0.080" down!

tektrans

If the PTV clearance is less than adequate you could have your pistons flycut while they are still in the motor so you wont have to mess with it hopefully.
May be worth it to go to a good performance shop that has done head and cam swaps etc.
I'll bet the tops of those pistons have plenty of meat on them just ready to be cut away so those valves will fit.

Scottd

So whats the general consensus? Will the 2 grand price tag net me an extra 35-45 HP like a good set of heads usually does or are my stock pistons just going to keep holding me back? I honestly hoped that the Edelbrock heads would be a bolt on operation.....

zwede

Oh, easily more than 45 hp! More like 60-70 hp with the heads alone. Your low compression is still holding you back, but the Edelbrocks flow so much better than the stockers.

Scottd

So assuming my pistons are stock and my cam is mentioned above.....these Brock heads alone will make a huge increase?

(are there ANY other small CC heads other than Edelbrock? 2 grand is just too much right now....)

tektrans

If all you are concerned about it chamber size why not just have YOUR heads milled down???

zwede

Nothing that will flow well. You can mill down factory heads, but it's not going to make much of a difference as they don't flow. By the time you fix up factory heads (new valves, guides, milling, porting) you've probably spent close to the same money.