Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Dreaded nozzle drip 17056200

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old cars:
Your cam and compression are alright . Correct timing for the situation is the number one starting point .
Kenth is on the right track if you are using a points distributor and you need more timing with vacuum advance at idle. Like Cliff said post results after stepping up timing with vacuum readings.

von:
In addition to the above make sure your secondary throttle blades are absolutely closed all the way. Be sure there's a little "slop" in the linkage rod that connects the primary and secondary blades. Hold the secondary air valves (flaps) open by hand and hold the carb up to a light to see if the sec blades are shut tight.

Cliff Ruggles:
Good advice Kenth but we're a bit early in the game here to start running 25-30 (or more) degrees initial timing.  Before that happens we need to know vacuum readings and how much timing it's going to take to get good idle quality.

The carb already has PLENTY of idle fuel for this application, but we're also assuming no fundamental issues either.

The cam may be "alright" for the application, but that remains to be seen.  It's only around 400CID and dubbed 9.5  to 1 compression.  If it's actually 9.5 to 1 and doesn't make at least 12" vacuum with that cam with only 12-14 degrees initial timing then it's seeing it as s pretty "hefty" camshaft for the combination of parts, or the compression ratio isn't as high as we think it is.

Doesn't mean it woln't work OK, but personally I consider having to run the timing clear off the scale at idle and open up the carbs idle system quite a bit more of a "crutch" fix than a good method of tuning.....FWIW.....

lightning boy:
68RS, you never gave the main air bleed sizes. Unless I overlooked this.

68rs/ss:
Took Sunday off.
Put carb back together today after checking everything carefully and really didn't see any problems. Although, I've only done a few of these and may have missed something. I wonder if the new idle tubes are plugged or something? I did run this on a 350 for a test fire last year and it did work ok then. So not sure. So, Put it back on engine and tried to do the test that Cliff had suggested. Really could not get it to run smooth enough to get any reliable reading at any initial advance. Vacuum was fluxuating between 10 and 15 in/va. Started at 8 degrees and moved up to 12 or so. Eventually, I did advance it to around 30 degrees and it seemed to work a little better. vacuum there was around 12, but not steady. Was really hard to get accurate reading as engine was "hunting" so bad at idle. I could get it down to 750-800 rpm . Hot restarts are not happening. I do not have vacuum advance hooked up.
It did smooth out when i cupped my hand over the choke to restrict the air flow. Seemed to like this. although, didn't cure it completely.
I've never had an engine this hard to set. I will be trying a different carb and different distributor in the next couple of days, just to see.
I am starting to wonder if I have a intake gasket leaking. It is a new Q-jet RPM and it did need to have some of the intake bolt bosses files down so it would fit.
This engine is a true 9.5. compression. Heads were cc'ed, piston/deck checked at .017 ands a .020 steel shim gasket to get a good quench. There were basically only two forged piston options to choose from, so it was a thought out build. I didn't want to deck block to loose right engine code for my car. So pretty happy to get what I did with the few options available.
If it turns out that this is what the engine personality will be like, I certainly have no issues with a cam change and using my cast intake. I want a strong, fun, reliable street engine. Something that can be driven on a day trip. Of coarse, I will run her through the gears once in a while too.. ;D
Main air bleeds are aprox. .113"

So tomorrow, i will get back to basics. Check plugs and may remove intake. Its easy sitting on test stand.
Will keep you posted with any new developments. Thanks for all the help. Definitely learning here.
Phil

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