this is a ? to an earlier post asking the differnce...ok i got a lg4 which is being totally hopped up,and i dont want a stinking comp keeping the timing down,so the ? is can i swap in a l69 ecm and/or will putting a l69 aftermarket chip also work???its an 87..the last ofthe carb

 

the computer "keeping the timing down" thing is a misconception. the computer is programmed to add timing from an assumed point. if the assumed point was 0 degrees the computer would jsut plus teh scale that has been programmed in until it is told to do otherwise by some other reading.
the timing being added in is no different than a mechanical advance really, as it is just an amount of advance that is possible with what was built into the system. if you change teh base, you change the total.
if you change that base point the computer does not know, it will jsut happily add in whatever timing it was programmed to add unless it reads the need to do otherwise.
the L69 computer is the same as the LG4 computer in this respect.
if you are looking to have a timing table that is optimized to your set up i woudl suggest custom tuning. it is not as big and expensive as many would lead you to believe and you can even do your own tunign with little or no prior experience without fear of hurting the motor

later
tim

 

The chip in the L-69 computer definitely has more advance being brought in sooner than the LG-4. It's not just the difference of the initial timing setting (0* BTDC for the LG-4, 6* BTDC for the L-69).

That being said, I have run LG-4s many times just bumping the initial timing up to the L-69's 6* initial timing setting and you get about 75% of the benefit from just doing that. Not all of it, but most of it.

You can buy aftermarket chips for these motors pretty cheap (or a replacement L-69 chip) for cheap, as your other alternatives.

Other than the chip, the ECMs are identical. No need to swap out the whole ECM to get what you're after.

 

Just curious, is there some emissions testing requirement that keeps you from just scrapping the comp.

 

z28 yes i have emission requirements where i live,w/o them i cant register it,therefore no drive which aint good..i dont care about if it passes cause i can get a wavier after i submit phony bills of repairs,but i need all the equipment on there for the visual inspection.w/o it it dont pass either.so i figure if i gota have it on there i might as well try to get it to run with it on

 

That explains a lot. One thing you can do is the suspention. They're fairly light have a good chasis and there are lots of aftermarket components. With just a little fender work you can get a sizable tire in the back.

 

thanks z28.i got all the goodies for the suspension.but now im lookng for a nice 9 inch or 12 bolt also...btw does anyone know of an outfit that setups the computer controlled quadrajets???