iroczguy86

im considering buying a 1986 z28 that has a lg4. can i take the tpi setup off my 86 iroc and use the lg4 motor and tpi in the iroc? and will it all bolt up to a 700r4?

sofakingdom

iTrader: (1)

Yes, and yes.

Not sure what impact it would have on "performance". AT BEST, it would be the same; no possibility of it being "better" except of course to the extent that your LB9 was defective and the LG4 is not.

Damon

Yeah, the LG4 and the 305 TPI motors were basically identical that year. Now as I recall the 86 305 TPI DID use a better exhaust system:

Manifolds with 2.25" outlets vs. 2" for the LG4
2-3/4" y-pipe, cat, over-axle pipe and muffler vs. 2-1/4" for the LG4.

So, basically you'd end up with a 305 TPI (stock tune will run it just fine) but a more congested exhaust system behind it, which will cost you some power. Of course, if you've already upgraded the exhaust system with header and such (or are swapping over the TPI engine's exhaust with it), you're golden.

yaj15

iTrader: (3)

Should work out fine. For 1986 the LB9 got the LG4 camshaft. That caused the LB9 to loose power from 215hp rating in 1985 to the 190hp rating in 1986. Torque went up 10 ft/lb to 285.

As others have said the LG4 cars got a very restrictive exhaust so that would be one of the first steps to get some power back.