Ok, I have tried to search for my answer and couldnt find it. I am putting a 305 from an 89 IROC in my car, and when i look up HSR parts on summit, it claims it only fits camaro 305s up to 1987 i believe. but i can find no mention of anybody having a problem with this on the boards... Anybody have any clarification?

 

Ok I put a HSR on my 89 IROC and this is what I noticed and presume the differance is. The 89 engines had a different angle on the two inner intake bolts on each side. The older heads had the bolts angled more and the newer ones had the bolts more straight up and down (less of an angle). I used the older style intake on mine and the two inner bolts on each side are at a funky angle. The head of the bolts touch on the outer most part of the intake but not on the inside. I was carefull not to over torque these bolts for fear of poping the heads of the bolts off. But it works fine and I've had no leaks or problems associated with it.

I can't say for sure that's what it is but that's the only differance I'm aware of or noticed.

 

it seemed like it was an issue with fitment from the lower manifold the the heads. thanks.

 

As noted bolt angle on center bolts was changed on late cast iron heads.
Some just redrill the holes or you can buy custom angled spacers to seat the bolt correctly