7a heads

[billegoat]

Found a set of 409147 7a heads. They have big valves, mild porting, ready to bolt on for $400 for the set. Is this a decent price?

 

[88hurstolds]

Price is right if they're actually big valve heads, check with a caliper... I've been burned before.
You mean 71-72 7a heads and not 85-90 7A heads right?

 

[billegoat]

yeah '72 model heads and the valves have been put in, hardened seats, oversize springs, this guy does most of head work for all the local dirt trac boys in ne ark.

 

[High Roller]

Grab them

 

[ChevyHeaven]

Mind if I ask the differance between the 71-72 heads and the 85-90 heads?

 

[86-blk442]

The ports on the early 7a heads are normal sized and the heads themselves are more performance oriented when compared to the later 7a heads. The 85-90 heads have tiny square ports which are great for economy but not performance. The ports will not match up to any aftermarket or pre 85 intakes without huge port mismatch problems.

 

[ChevyHeaven]

Yea after further research it seames the 307 had smaller everything really, exhaust ports swirl ports etc.
Just for sake of discussion though, couldn't you theoretically use the 307 heads on a 350 and upgrade to an aftermarket 307 intake manifold and have a fuel efficient 350?

 

[DoubleV]

Yea after further research it seames the 307 had smaller everything really, exhaust ports swirl ports etc.
Just for sake of discussion though, couldn't you theoretically use the 307 heads on a 350 and upgrade to an aftermarket 307 intake manifold and have a fuel efficient 350?

Yeah, theoretically. In practice though, I don't know if it would work out that well but you would need to use the matching A5 307 intake with those 7A 307 heads. If you went with an aftermarket ( aka 'normal' sized runners/ports ) intake, it wouldn't match up to the tiny intake ports on those 307 heads. That wouldn't be good for anything.

Other big differences between 350 7a heads and the 7A 307 heads, the 307 heads have no center divider in the middle exhaust ports and they have smaller valves. Overall 307 heads have no advantages that I can see in any application over another head.

 

[86-blk442]

I agree with DoubleV no sense in putting 307 heads on a 350. I had a 350 with 5A 307 heads on it and it was OK. But then I went to early #5 heads with W31 valves and it was a world of difference. Mileage didn't change. A correctly built 350 can be just as efficient as a 307 especially with overdrives, and gears. It'll get up and go better too.

I don't see how using heads that don't flow well with tiny ports and valves could be better than earlier free flowing heads.