I just visited my girlfriends mothers house and found a 1985 IROC ( LB9) W/ T-tops behind a bunch of trees. The car is on blocks and has some minor body damage. Over all its a great project car. I dont know what ROP's there are yet. Still learning from here, I think I have been reading for 6 hrs straight! I did notice the rear had drum brakes and I saw that all rear disc came with Posi. I am hoping that it has it.. My question is if the block has a 4 bolt or a 2 bolt main?
I also checked on value for it and got mixed numbers from KBB.com and NADA.com a $1000 dollar difference. one said $1800 and the other said $875. What gives? BTW Great site!

 

since it doesn't have rear discs my guess is that it doesn't have posi, and i'm pretty sure that its not a 4 bolt main block sorry but great find

 

as far as I know that is a 4 bolt......and it probably doesnt have posi,but you never know.

 

sounds like a 305 RP0...305 4 bolt????dont think soo

 

It is not a 4 bolt. It is a 2 bolt motor in there. AFAIK the only 4 bolt motors came from the vettes and trucks

 

yes i was also understanding the only 4 bolt main blocks came from vettes and trucks

 

FYI
The 1985 system used a GM Part #1226870 ECM and had a Mass Air Flow (MAF) sensor and a MAFS module to control the power and burnoff functions for the MAFS. In 1986 two relays replaced the MAFS module and the Electronic Control Module (ECM) was changed to a GM part #1227165.

 

4-Bolts-Vetts/Trucks

Just Trucks

Later

 

if the rear is origional to the car it's a posi.

 

That was the first year for the TPI in the F-body. It was actually a pretty stout motor for it's day. It came with a flat tappet cam, but it was the "good guy" cam pretty much straight from the L69 HO 305. It also had the slightly higher 9.5:1 compression ratio thanks to flattop pistons. With the 5-speed and a decent ratio posi rear they were legit high 14 second cars from the factory. This was an unbelievable performance bargain in 1985- easily the equal of 5.0 Mustangs of the day (which were still carbureted). Just nobody knew what to do with TPI motors when they first came out- we all sat around, scratched our heads, pointed to the weird looking intake and kinda wondered if there was any way to make them go faster. We legitimately thought there was nothing left to do besides slap some headers on them and try to figure out where to mount this weird "O2 sensor" thing! Ha! It's hard to describe how intimidating EFI was when it first hit the scene- you had to live through it.

 

305ci=2bolt always. unless modified.

 

i bought a 92 z28 5 speed that came with a posi from the factory. im pretty sure an iroc would have a posi also