When I bought my replacement heads for my 305 TPI I asked if I could put 194 heads on it and the man said "no the angle on tuned port heads were different and the intake manifold wouldnt bolt up cause it was at a different angle". I was always under the impression that all SBC heads were 23* heads and you could pretty much plop TPI on any small block with the proper ECM. Can anybody verify this? Or any info? Thanks.

 

It's my understanding that all Gen I SBC have to same intake manifold angle and bolt pattern until the Vortec heads came along.

 

55-85 are all the same intake bolt pattern. The intake bolts are perpendicular to the head. 86-95 the 4 center bolts are at like a 60* angle to the head, and Vortec heads 96-02 only have 8 intake bolts total and they also go in at an angle to the head. All stock small block chevys had 23* heads just the bolt patterns are different. U can use an old style head you just have to modify you intake. Elongate the 4 center holes, some might not recommend this tho. $.02

Seth

 

I'm pretty sure the split is 86-down for the old style and 87-up for new style

 

So its just the bolt pattern. So you couldnt just throw a TPI intake manifold on any set of small block heads. If I were to buy "aftermarket" heads how would I go about getting the correct bolt pattern? Thanks.

 

Yeah I thought it was 86 or 87 but I was still half asleep when I typed that. You can use a 85-86 TPI base or just elongate the middle holes on a 87 up base.

Seth

 

Well I learned something today.

 

Well thats good I have an 85 or 86 TPI in my 89 IROC. So If I ever decide to change to block I can use what I have. Thanks for all the info.

James.