I'm considering swaping my LG4, 5-speed to a GM crate 330hp or 355hp. What problems might I encounter? Computer and chip? Fuel delivery, etc. A list of parts that you used successfully might help all future swappers.

JamesC

 

Mine was a pretty much direct swap, my first swap working with my father, and it was a direct bolt in. But my LG4 being an 84 had no knock sensor which would need to be changed. The computer runs it fine, I did tune the quadrajet with rods and hangars, but it ran fine on the stock one. Just gained a noticeable SOTP feel with the carb parts. There might be a conflict with flywheels, but I just used the one on the LG4, which I will mention only lasted 8 months behind the 350. But mine was a 700R4, and I dont know the faintest thing about standard shift flywheels.

 

The 330 HP crate has Vortec heads, which require a special Vortec intake manifold. Neither has exhaust cross-over passages in the heads, so you need to plumb exhaust up to the intake manifold in order to have a functioning EGR valve (although you might be able to get by without it). Both have one-piece rear main seal, so you need a 153-tooth one-piece rear main seal type flexplate or flywheel.

355 HP (I assume you mean ZZ4, anyway) has a roller hydraulic cam, so a melonized distributer drive gear is needed. No changes required to obtain adequate fuel delivery as long as it's in good shape.

The computer should be quite happy as is. An upgrade chip might help performance a little, but the stock chip will at least work. Reports vary as to whether a 350 knock sensor and module are required, but it seems the TPI guys have more problems with that than carb guys. Ignition coil and module upgrade might help avoid high RPM issues.

Exhaust upgrade to headers wouldn't be a bad idea.

 

tt

 

My swap was an L69 to a 350 crate with
two piece rear main seal. This is about the easiest swap possible. The only thing
I changed was the secondary metering rods from CKs to CEs. The starter, flywheel, carburator, distributor,all
sensors and computer(upgraded Jet chip) transferred over. I did replace the stock exhaust manifolds with headers and put in a new pressure plate and disc.