I have an 84 l69 with a cc carb and t5 trans
and a 3:73 rear with rear discs.My new engine runs great except at wot seems to bog does this mean i need to increase the size of the secondary rods? also it seems when i first start and run the car it runs better when it is fully warmed up there is less performace.

any help appreciated.
Thanks
Dave

 

Sounds like two different problems. The bog at WOT is a common q-jet issue, see the tech articles for adjusting the secondary air valve opening and tuning with the rods & hanger (you'll likely need smaller or richer rods, not larger).

The other sounds like a closed- vs. open-loop issue. Perhaps someone else can chime in on that one, but that also may just be an adjustment.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

How can i tell if my car is running in open loop mode? No warning lights are on.As far as running better when cold i thought maybe was because a needed a better chip to enrich the fuel ratiio and advance the timming because doesnt it run richer on warm up? then lean out and isnt this done by the chip.
I know the choke too. But i thought the chip had something to do with this too.

dave

 

Our carb computers aren't very smart, so they can't tell you when they're running in closed loop.

The difference is that when cold and in open loop, it runs off of a "baseline" curve for fuel enrichment. When in closed loop, it reads the O2 sensor and adjusts accordingly. This occurs when the water temp gets above 110 degrees or so.

For their HO 350 conversion kit, GM supplies a different chip for the computer. You might try getting ahold of one of those. The other possibility (hey, nobody else jumped in here) is that your timing isn't quite right, and/or your knock sensor is retarding things too much. You didn't say what all you modified/changed with the 350, but one common suggestion is to get a 350 knock sensor and module (also supplied with the GM conversion kit).

Hope you can sort it all out.

 

This may or may not be part of your problem, but I was having trouble going to WOT from a stop and sometimes from a roll. Turned out my TPS was bad, and was running the primaries too rich. If you want to check it's operation, I think there's a tech article on this.

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D.R. Stevens
1984 Trans Am 305HO L69
all the usual external/free mods, original engine
1991 Firebird 305 L03
bone-dead-slow-stock

 

The ECM does not work the choke. There is a 12v power wire going to the choke thermostat, but it is "open loop" (no feedback to the ECM). It just opens on its own as the voltage warms up the bi-metal coil.

That "Choke" light in the dash is actually tied to the alternator. Go figure...

 

five 7 kid

i would try the zz4 conversion kit chip except it is for a auto tranny mine is a t-5 manual.So i was just gonna try the 305 jet chip. I'm not sure but for a hundred bucks worth a try.

Dave