Which is a better performer? l03 or the LG4?

Stock for stock that's a close call. I'll go with the TBI motor, but not by much.

Stock for stock I would also go with the tbi motor, but once you start modding the lg4 has more potential. The heads on the lo3 are very restrictive.

Ben

1987 LG4

all the LG4 could be and nothing the L03 was

L03 all the way.

I am going to have to agree with Damon. The LO3 is probably better stock, but as soon as modifications make their way into the picture, the LG4 will prevail.

The L03.

which one performs better with mods?

The LG4 changed considerably over its life span. So it's impossible to make this comparison for all LG4s. I'm going to confine myself to the later LG4s, with flat-top pistons and electric fans.

The 2 motors (and the cars that they were installed in) are very similar, subject to year model differences. I doubt either one had a significant performance advantage over the other, stock, as they came.

The later LG4s had the same higher compression as the L03, but had far better heads. The exhaust was the same on them (pitiful) and they got the same weenie cam and the same grocery-cart gears. If each of those things was upgraded properly, the LG4 would be considerably ahead of the L03, especially if it's a 87 LG4 with roller cam.

The L03 will stomp an early LG4 with the power-drinking clutch fan, low compression, etc.