Hey all,

I have a 1988 LB9 Iroc that has a very bad rod bearing knock, and the cost to rebuild it is way more than I would like. Instead of a rebuild, I am considering swapping a new engine in. I want to keep the engine as era-correct as possible. My question is, can I just find any old GM 305 engine from the 1980s to swap into my car, and just add the TPI setup onto it? Is that possible to just switch the TPI setup onto any GM 305 engine and call it good? Thanks.

 

Almost.

The dipstick moved from the driver side to the passenger side in 1980. If you use an engine from earlier than 1980, the dipstick tube and factory exhaust manifolds don't play well together.

The rear main seal type changed in 1986, so you'll need a flexplate that matches the rear main seal type of an '85-earlier engine.

The intake mount bolt angle changed for the middle two bolts on each side in 1987. Your 1988 TPI base can be modified to accommodate older heads if that's all you can find.

The valve cover type changed from 4 perimeter bolts to 4 center bolts in 1987. Not a big issue, but I have heard of perimeter bolt covers interfering with the alternator of the '88-later accessory type.

The early 3rd gen carb, crossfire, and TPI heads (up to 1986), and the later TPI heads ('87-'92), were the best 305 heads the factory made. Avoid TBI and earlier truck 305 heads (although if you don't upgrade anything on the TPI, the TBI heads will probably work okay). The early truck 305 heads had really small valves.

 

Ok, thanks. I will most likely be swapping in a 1985 Iroc LB9 block that I have on a parts car. I will keep the 1988 700R4 transmission in the car, and mate the 1985 Iroc LB9 with the 1988 700R4. So would I need to change the rear main seal/flexplate to accomodate that? What other work do you guys see that would need to be done to make those two compatible? Thanks guys for the help.