Hi!

We swapped the worn out LG4 to a L69 with all agregates.

The cc q jet from the l69 needs a rebuild and the cc q jet from my lg4 is rebuilded already.
I opened both up and they look the same inside, except the pump accelerator spring (black in l69, green one in lg4, the black does not work proper).

Can i use the carb from my lg4?
Is there a difference? I read somewhere here, that the jets are different?

Also i did not change the computer / chip in my car.
The car runs and drives without problems as far as i can tell until now.
Does it realy make a difference?

Ps: I use the complete oem lg4 exhaust system.. Should also swap this to 3", heh?

Thanks !!

 

I would guess the Q-Jet is okay but the prom for the L69 is different. Properly maintained and tuned Q-Jets are hard to beat. As for the exhaust at least go to the LB9(?) exhaust manifolds that are free-er flowing. Flow Master makes a cat-back system called Force II. Don't know if that is still available or not.

 

Hmm.. In the prom section of the board ppl are talking about injected birds.
Can i also mod this prom of my car as it controls the cc qjet? Like readout the l69 prom and write it on my prom? A friend of mine does chiptuning (business) and has all the devices needed. Would be a good idea, because the l69 has an other cam too.
By the way, how do YOU tune the qjet for the right mixture if you upgrade components?
'cause I've got an edelbrock performer 2101 laying around too

The exhaust will be a problem, because i'm in europe / austria, where its rather hard to get (cheap) parts.. Any suggestion on aftermarket parts? Or just any that fit, with 3" back?

My catback is a flowmaster 80

Thanks for your help!

 

The carburetors should be the same except the hanger/rod combo is a bit more rich on the L69. Your LG4 carb will work perfectly; just swap the hanger/rods and you'll be fine.

The computer is set up differently on the L69 - it has a more 'radical' timing program which what helps give the engine more power. If you've added all the sensors then you will want to replace the PROM so you can use the computer to its max efficiency.

 

thanks for the info.. this explains why it runs in idle at 3000 with the lg4 carb and with the l69 carb normal at 500-1000 *haha*

ok so I´ll try to get this prom
thx

 

That doesnt make any sense. Check your idle screw. The hanger/rods he is talking about is on the secondary side, they affect WOT not idle. Swapping the secondary rods/hanger over is easy, just find a video on youtube and dont drop the rods into the carb.

You might be able to swap your old ECM for a later ECM/PROM from a Monte Carlo SS L69 car. The only thing is that the Montes have autos, so that SES light will be on all the time. You didnt specify which year your car is so I cant tell you for certain. I have an 86 and swapped over to an 88, IIRC and its been running good since. The L69 proms are getting really hard to find for our setups.

 

Hm I thought this effects idle maybe too.

The L69 came from a manual trans. '84 and mine is a '87 automatic trans.
Had to swap the flywheel and to mod the quadrajet gas arm for the automatic-wire.
The 2nd map sensor is without function aswell as some cables.
Removed air condition too, as it wasnt working anyway.
Also the o2 thing for the exhaust has found its way out of the car

I talked to the friend of mine who gave me his l69 and helped me with the swap.
He said he'll give me his prom too and if i want the hole box, but he does not think the comp is the same. Do you know if these models proms are fitting each other?
Wires, sensors, plugs..?

 

If the 84 is non computer controlled, I would stick with the 87 LG4 computer controlled carb you have already and just swap the secondary hanger and rods.

I dont know too much about the 83-84 L69 cars. Some of those older cars did not come with knock sensors or electronic spark control. You are going to have to search and figure out what is different. Since your car is automatic already, you might be better off looking for a monte carlo SS PROM and/or ECM.

 

Hi, i have a computer and prom for a 1984 z28 auto it was a factory h.o. car and would sell it cheap and ship it to you, i have an 1985 iroc which was a factory l69, 5sp, 3.73 gears so i don't need a computer for a auto car. let me know Mark.

 

The differences between the LG4 and L69 were the exhaust system (manifolds to tailpipe the L69 got bigger stuff), chip programming (primarily the more aggressive timing curve on the L69 chip as well as the higher 6* initial timing spec on the L69), the cam (again, L69 cam was significantly more aggressive), secondary metering rods and hanger in the carb (L69 getting the "good guy" stuff in this regard) and the air cleaner assy (single vs. dual snorkel). Other than that, you couldn't tell one apart from the other by looking at them. Most of the magic happens "out of sight".