I just rebuilt my first quadrajet #17058213 :Smarty: Cleaned everything very good and replaced all parts included in the rebuild kit. Mounted the carburetor on my engine and pulled the slow idle adjustment screws out 1 1/2 turns and the engine fired right up with no problem. It seems to run just fine. :bglasses: The problem is that it has like no power. I removed a CC quadrajet that I have been running for the past month with no issues (absolutely no wires or computer hooked to it) and it had a whole lot more power with the CCC (got horrible fuel mileage) What could my problem be?
Alright, I brought the slow idle mixture screws out another full turn, so they now sit at 2 1/2 turns (seems to idle a little better in gear now) but the slow idle mixture is just that, it only controls the mixture at a sitting idle right? The choke is opening just fine on it, so we'll scratach that. I took it out for a good hard test drive, the rolling WOT is just fine, secondaries open up and it gets going real good. Its the throttle response and from a stop accelleration that is horrible.
The idle mixture screws do not affect the actual fuel/air ratio of the idle mixture, but the volume of mixture discharged at the idle port, at idle. The idle system does contribute some fuel off idle via the transfer slots. I would make sure your accelerator pump is providing a solid shot of fuel from closed throttle all through WOT. If you did not use a rebuild kit with ethanol resistant parts, fuel can deteriorate those parts fairly quickly. The accelerator pump is #1 here.
You just installed an emission calibrated carburetor onto what engine? Were any modifications (tuning) done to the carburetor to set it up exactly for the application? The NAPA kit does NOT contain the high flow needle/seat assembly with Viton tip needle. It should have had a white pump in it with a blue seal on it. The seal is not the latest grade of Viton, but it will hold up for a while. Did you replace the float?....Cliff
I did replace the float. I didn't do any adjusting or tuning besides the idle mixture screws and the float height adjustment. The engine is a completely stock 1973 SBC 350 with 1.72"/1.5" valves and even a stock cast iron intake
I'm thinking the 17058213 was a divorced choke Chevy truck carburetor? Did it have #64 main jets in it?.....Cliff
I was told it has #63 jets, I didn't personally check them during the rebuild. What jets should this engine be running?
It's certainly an "odd-ball" carburetor as far as q-jets go. It was produced well after the newer APT carburetors had been released. It appears that GM didn't switch over to the hot-air choke carburetors on truck applications until 1979. The 77 and 78 units were still divorced choke, but used special single main airbleed castings. I set one up about 6 months ago for a 1970 402 BBC. I still remember it having very small main jets, 64's, and pretty large metering rods, which were tapered. It uses the early APT system, which really isn't adjustable unless you remove the cap over the adj screw (between the mixture screws) and can get it free'd up. In any case, it took .071" main jets to get the fuel curve up to par, combined with a custom tapered primary rod at .044" on the largest upper portion. I replaced the APT screw in the baseplate with one we cut on the lathe, and put a spring under it. This provided full control of the part throttle A/F ratio from rich to lean. The carb ran flawlessly on the test engine, and not a word from the customer, which usually indicates everything is fine.....Cliff
In no way am I an expert on carbs like Cliff is however this is what I have found with the q jet: The idle mixture screws will effect the "from a stop acceleration", tune them to get the highest vacuum readings with the wheels blocked, vacuum advance disconnected and car in gear. This makes a huge difference in how the carb transitions from idle to part throttle in my experiences.
I suspect one thing: unless the ECM "sees" the electronic carb, it will fix the timing advances. No matter what you do to the carb, unless it sees the mixture control solenoid on that circuit, it considers the carb disconnected. It is programmed to then fix the timing, eliminating ALL of the performance the engine is capable of. Unless it "sees" the 12 volts on the ground side of the solenoid circuit, which it uses for confirmation of control, that is the result. I suspect that if the computer is "scanned" for codes, one of the codes will be a 23. 23 means that the mixture control solenoid circuit is open. Those are the facts. Ray
