Project"Z"

I have an 87 z28 305 , 5sp lq4 that needs rebuilt that i want to use for autoX. my local rules allow me to retro-fit so i want to convert it to h.o. L69. my question is to avoid all the cc qjet mess, can i replace the carb with a older qjet and hei dist and get rid of the ecm? what else is involved?

five7kid

iTrader: (14)

The main differences between an LG4 and L69 after '85 were the cam and exhaust. Minor calibration differences in the carb and ECM.

Personally, I would keep the CC q-jet, as it won't be a power limiter, and will "tune" itself. Not sure what all your rules do allow, but your money would be better spent on exhaust.

Oh, '87 had roller cam. 3rd gen L69's were all flat tappet. Would you convert to flat tappet?

Project"Z"

No, thanx for the reply. I havent seen all the specs but the ho cam had very simular lift numbers as tha 350 tpi roller cam. not sure about lobe sep, etc. i was gon use tpi roller,dual snorkle aircleaner, retro qjet and hei, 3 in exaust and remove ecm. im trying to see all the facts and then decide though i have already removed the a.i.r. the rest is stock. i saw a thread about using the monte ss ecu. hard to find now i bet. I also was thinking losing the ecu would be cheaper than replacing all the sensors, etc. SCCV (vermont) allows me to upgrade to any 3rd gen parts, im also allowed up to 15 pts before they move me out of F stock. This may leave me able to run a inch drop springs and hps brake pads( 3pts and 1 pt )

Damon

I'm not familiar with the rules of that class. Exactly what are you allowed to do to that engine before you run afoul of the tech crew?

I think you have a good plan. The L98 TPI cam is almost an exact copy of the flat tappet cam used in the 86-down L69 motors, except it's a factory-style roller cam. Swap away! FYI- the later factory LT1 cam is again almost identical as well, just with more lift. Amazing how GM used only slight tweaks to the original L69 cam specs for YEARS AND YEARS, right up through the "Gen 2" LT small blocks!

Your exhaust system is the OTHER big difference from the L69. The L69 used different (larger diameter) exhaust manifolds, larger y-pipe, larger cat and larger cat-back from the factory than the "pea shooter" LG4 exhaust system. In short, everything in the exhaust was different from the factory.

The CC-QJet was different between the two motors ONLY in that they used different secondary-side metering rods (CH for the LG4 vs. DR for the L69) and the hanger was a different letter (K hanger, I believe, for the L69- still available from many sources). Literally no other differences in the carb other than that.

Chip programming was different between the LG4 and L69 (a more aggressive timing advance curve for the L69). And the L69 used a 6* BTDC base timing setting at the distributor vs. 0* BTDC for the LG4. There was no L69 offered in the Camaro in 87, but the Monte SS still offered one. I am not sure if you could use the 87 Monte SS L69 chip in the Camaro. Maybe you can. If it MUST be a stock equipment chip in the ECM (just different year/application), I'd use an 86 L69 Camaro chip in it. It'll never know the engine has centerbolt valve covers on it! Otherwise, go aftermarket for the chip.

Air cleaner was different between the two also. Single snorkel for the LG4 vs. dual snorkel for the L69 in the F-body.

makaveli09

you can go with the ZZ4 chip as well. basicly a L69 chip with the EGR function removed.

Damon

Good point. Good point. They're rare as hen's teeth, though.

BumpaD82

When I got my '82 it had been changed to a "70's" quadajet and HEI ... The cc qjet, cc HEI, wires and ECM were in a carboard box

I autox'ed it that way one season ...

~DaVe