Ive got an original 70 350 low compression 2 bbl Cutlass. It has the #6 heads on it, all original never touched. Ive found some #5 heads that have been fully rebuilt for $250, pretty sweet deal. Plans are for a Performer intake and 4bbl with a 3:91 posi I picked up. Any suggestions on a cam and tourque converter combo? I run 275x15x60 out back, but may go to a smaller 255 tire. Oh yeah, do I need to get the thin original style gaskets to avoid losing compression? I just read that another thread. Thanks!

 

Yes the shim gaskets would be best.
Exchange the regular Performer for an RPM, you'll have the gear for it.
And an Erson Hi Flow AH would be a good cam for you. Let me know if I can help there.

 

Assuming your 6 heads don't need to be rebuilt there is not really a big difference in my view. There is no significant difference in #5 and #6 heads in stock form....If all valves are same size etc. Combustion chamber should be pretty much the same if untouched. Can't really say flow would be much different either. Only difference may be in the presence/absence of valve rotators (which may have come on 7's and 7a castings). More learned people will have additional information. If you are picking these up because your 6's need rebuilt OK. Just be careful about the quality of the rebuild. Caveat emptor!

Good luck

 

My #6 heads seem to be fine, they have just never been touched in 44 yrs. I thought it may be cheaper to install these heads than re-work mine. The builder is experienced, but was stuck with them when the owner never showed up to pay him. Im limited with quality shops where I live so I thought this may be cheaper. Thanks for the advice on the cam. 2nd time ive been recommended that one.

 

Haha! I know the 3:91 is a bit extreme, but I really want it to get up. I bought it thinking id install a 2004r tranny. I should have spent the money elsewhere, but if you're going to smoke the tires it might as well be 2 of them through all 3 gears!

 

Im not sure, ive never pulled the cover and looked. Feels around 3:08 or higher. rides real nice at 60 mph. I thought the 3:91 might be okay with the taller tires.

 

Well, the #5 heads i was going to buy are gone, so that settles that. Apparently they were being sold because a customer hadnt paid for the work done, and he freaked out when he saw the ad on Craigslist! I knew the deal was too good to be true. Would have been bad karma anyways. Thanks for any advice, and Cutlassefi I will definitely get in touch with you when it comes time to choose my camshaft.

 

#6 heads on a 70 olds 350 are the same 2bl or 4 bl fact!!

 

I am sorry, I am not sure I am following. What?
What does 2 barrel vs. 4 barrel have to do with the heads and what does your statement have to do with this thread? Not trying to be an A$$ just don't understand.

 

Um, yeah. There were no "2bbl" or "4bbl" heads on any SBO as far as I know. The only "different" ones were W-31 heads that had larger intake valves.

 

Correct. We're not talking about a Ford here. ALL SBO motors within a given model year used EXACTLY the same head castings. The only difference is what size valves were installed. Chamber size is exactly the same. Olds varied CR with different depth piston dishes, not the heads.

 

what he said