Lg4 Vs Lo3
 

what are the main differences in these two engines? My 86` has the lg4 while my wrecked 88` has the lo3. Trying to find out like which set of heads are better, which block would be best to use.

It's a mix.

The LG4 without a doubt has the better heads.

The LO3 will have a roller cam block. If roller cam is your bag, it's the better block. Other than that, it's which one is in better shape.

could i use the lg4 heads on the lo3 block. I plan on using the lo3 block after it is rebuilt but until i save up for some better heads( vortecs) I would want to use the best heads that i have now, which are the lg4 heads

Ported with 1.94" intake valves, those LG4 heads will rival stock Vortecs for flow. Neither has the best valve springs, but getting the LG4 heads set up for higher lift is simplier than on Vortecs. Screw-in studs are always a good idea, which none of those heads have.

Consider this route: Disassemble the LG4 heads and have them checked for cracks. If okay, have the seats roughed in for 1.94" intake valves. Take them home and port the heads (you can do this yourself with a die grinder and Standard Abrasives Deluxe porting kit), following the SA "Guidelines for Do-It-Yourself Porting" (included in the Deluxe kit). Take the heads back to the machine shop for installation of screw-in rocker studs and valve grinding. Reassemble with new intake valves, good valve springs and seals.

Doing this you can still use a "standard" SBC intake manifold, cost won't be that high, you won't have to buy another set of heads, you won't have to shave the heads to get the proper combustion chamber volume.

Any particular reason you're rebuilding the LO3 block? I normally don't recommend that since 350 blocks are relatively cheap, and well worth it $'s/HP wise. Unless a 305 block is usable as it is, don't use it. This is especially true if you really want Vortec heads.

I have 2 305 blocks in good shape and it`s just going to cost me $120 to have the block cleaned, bored and cam bearings put in at work.

If it's bored, it'll need new pistons and rings.

If you need to spend money on the block, you're better off spending it on a 350.