OK, Here's the story. My brother bought an 87 Iroc with no motor. The previous owner had sold the engine along with the wiring harness and computer. We found a complete running TPI in an 86 T/A (for $200) that included the trans, all wiring, ECU, disc brake rearend, all the A/C parts we needed... Only catch was that we had to pull it, no problemo. The emission decal said 5.0L and the 8th vin digit was F - which is supposed to be 305 right? When we got the motor out we saw it had the familiar 5.7 cast into the block on the bellhousing area. Then we pulled the pan to see what we had and found a 4.00 inch bore, two bolt main block.

Apparently someone swapped it out at some point, but I'm not sure what else was changed. I know the injectors were different between the 305's and the 350's, and that the intake and runners were the same, but were there any other differences such as the computer or MAF sensor?

Also, what would you guys do while you had the engine on the stand? We are doing an oil pan gasket and rear main seal, as well as replacing the wp and all the tune-up parts.

 

New timing chain couldnt hurt. Honestly, your already there. As for everything else, in my experience if you have a good shortblock and your not looking to go 500+ hp on it all day long OR 6000+ RPM, leave it alone! I had a 4 bolt shortblock with a nodular crank, LT1 Rods and Hyper-U pistons in great shape that I pulled for a buddy and he dissasembled it and never touched it again because it was too much money to do the machining for the re-build.

Throw it in their and have a blast! Thats what hot roding is all about man! If I were you...honestly this is what I would do:

Drop the EFI, switch to carb (this coming from a guy running TPI). You will end up enjoying alot more siplified problems as opposed to a problem that makes no sence, oh and your engine wont fall flat on its face at 4800 rpm haha.

Edelbrock RPM Air Gap (or Summit Stage 3 intake)
Then get a cam, go LT-1 if you can but if your block isnt a factory roller I wouldnt try, $800 on a cam is expencive IMO. But stick to about 220-230 degrees of cam to make it fun on the street.
Get a Corvette stall convertor for $150 bucks. They stall at about 2000.
Dont forget to upgrade your valve springs.
And ditch the stock exhaust for the love of god haha. Headers and some pipes man, big time.

Run that. You will be in for under $1500 if you do it right and you will have a fuggin blast. Trust me, its a million times more fun to run a little bit of car than no car at all! Haha damn, thats alot...I guess the jist of this rant is dont get stuck on thinking you have to upgrade everything to have fun.