i am at a standstill.i have an 85 trans-am with the LG4 305.I purchased a good L69 motor from an 84 trans -am for next to nothing.I am debating on wether I should rebuild the L69,work over the heads (416 w/ bigger valves),comp 268 cam,weiand intake.or should i keep the LG4 block,and put all these parts on that block.the little bump in compression would be nice,along with a fresh rebuild,but would it be worth the trouble of pulling the entire motor.unfortunately this is a backyard job,no lift or garage.any input from someone with more experience in this area would be greatly appreciated

 

The '85 & '86 LG4's had the same compression as the L69's.

The main differences between your LG4 and the L69 were cam, exhaust, air cleaner, and some slight differences between PROM tuning and carb jets. L69's also had an electric radiator fan instead of an engine driven fan. All of these things are easily "done" to an LG4.

It's rarely "worth it" to rebuild a 305. The only reason to consider putting the L69 in is if it is in much better condition than your LG4. Otherwise, the cam and exhaust, along with an air cleaner change, will more than make up the shortcomings of your LG4 compared to the L69.

Both heads are the same, so if you want to put in larger valves and clean up the ports and bowls, that's worthwhile to support the upgraded cam (along with upgraded valve springs, of course).

Which Weiand intake, specifically?

 

I thought the L69's were 9.5:1 and LG4's were 8.5:1,maybe i just misread some info.if they are indeed the same,then that answers my question right there.i have a weiand action plus dual plane manifold on it right now.i was planning on putting bigger intake valves in the heads with some porting.i also have some shorty headers and a cat bak exhaust.any recommendations as to which springs to use.the cam is a .454 lift.

 

In '85 the LG4 compression went up to 9.5:1.

Comp 981 springs would be a good match.

With all that, wouldn't matter if you used the LG4 or L69 engine. Either one would wake up equally well. Just use the one that has the shortblock in better shape.