Machanically (parts), what makes the difference between the LG4 145 HP and the LG4 150 HP ? I am not sure if its different pistons..heads or what.
Any Info would be great !

Rod
Phoenix, AZ.

 

i think the only difference is improved(better flowing)catalytic converter-possibly revized ECM programming.There is no difference with the engine.

 

My '87 Iroc LG4 had a whopping 165hp

 

The difference was in the catalytic converter. The 145HP used the old pellet style converter while the 150HP used a modern monolith style.

 

GM used old hot-rod tricks to increase performance on the L69 engine - which was a factory hot-rodded LG4 motor.

The later LG4 motors got some minor updates that others have mentioned but they were not too much to write home about. The LG4 can be made to perform well but you are going to have to be willing to do a lot of work.

The good news is that many of the same speed parts that you can use to upgrade the 305 you can move over to a 350 motor if you choose to at a later date.

 

Thanks everyone for the info !!

 

85 brought the KS to the LG4 along with more aggressive timing and more compression. 87 brought the roller cam to the motor.

 

Also don't forget that in '86 the LG4 got an electric cooling fan. Less parasitic drag. I think that was the majority of the 10hp increase from '85 to '86.

 

'87 also had new heads with a more efficient combustion chamber design. That alone is worth at least 5 HP stock, and at least 10 HP in a more serious build. The LG4, as used in '82-'84, actually arrived for 1980. In the '80 Z28, with a single 2.25" pellet cat, it offered 165 HP. I suspect it was still using the LG3 cam, which I think was gone after '81.