Hey guys,
I've done some research but i still have some questions.
I have a 85 Trans Am which i believe was the first year of the TPI. The car has a 305 with a knock and I want to replace it with a 350. The problem is, I don't know what 350 to get because I want to get an L98 but I don't know if the L98 would match the bolt pattern of my 85 tpi. Was the bolt pattern the same on the 85 vette tpi as the f-body tpi when it was introduced? I would also like to know why some people keep their 305 heads and put em on the 350. Is this actally better or is it done when you don't have the money for 350 heads?
Please don't suggest any mods to the intake manifold since i want to keep the swap as hassle free as possible since i wont be doing the work.
Thanks

 

If you want to keep it hassle free then you will take the heads and intake from your 305, and put it on the 350 shortblock. A block is a block, is a block. The bolt patterns dont change.

The reason that people put their 305 heads on a 350 is because they will raise the compression ratio, which means more power (but also higher octane gas).

I'm currently in the middle of swapping to a 350 from my 305 LG4. And I'm just building a short block and putting the top-end from my 305 on top of it, and calling it good.... frankly I just want to drive it again lol.

 

I thought that the bolt pattern on the heads changed in 1986. Also, my 305 heads would have to be taken to the machine shop since they are really old and probably need new seals and stuff. I think it would actually be more expensive. I thought as long as i bough a pre1986 350 my 85 tpi would bolt on without a problem. I'm still confused. Can someone else help me figure this out?

 

How much will the comp. ratio be? and is ~93 octane enough then?
any suggestions about the power output?

Thanks
Pat

 

The bolt pattern that attaches the heads to the block did not change. Since you want to keep your TPI unmodified, and it bolts to the heads, keeping your 305 heads and putting them on a 350 shortblock would accomplish those objectives.

I'm doing the same thing (although not TPI). I'm using pistons in the 350 with a slight dish to keep compression down. You can also use a composition head gasket of approximately .040" compressed height to do the same thing.

I know you want to keep the costs down, but it's typically a good idea to put 1.94" intake valves instead of the stock 1.84" when putting 305 heads on a 350.

 

i just found out that having an 85 ecm makes things a lot harder for swaping from a 305 to a 350. whats involved in that?