Hot Rods Quadrajet With New High Rise Intake Off-Idle Stumble

I didn't want to question the rebuild but I was going to say main well plugs leaking maybe. Lippy

 

Would help to know the identification number of the Q-Jet.

If it is a '69, like the engine, curious as to what you did with the APT?

Also, some of the FLAPS kits come with the "windowed" fuel valve seat, which should not be used on the earlier Q-Jets.

Jon

 

Just wondering if you have spoken with your carb guy? Running rich is one thing, but if you are in fact getting raw fuel into the crankcase in any substantial quantity that needs to be addressed before you wipe out the bearings.

 

You had @squirrel working with you, stick with that. If you start listening to 15 different people,all you're going to do is chase your ass in circles around the shop.
I still have one of those intakes I ran years ago, with a Quadrajet. They used to be the ticket in the "stock" classes on dirt.
In general, unless you REALLY know what you're doing (and obviously you don't) , don't ever drill anything on a carburetor. Take that from somebody who has ruined several things based on some other knuckleheads advice.
Good luck.

 

Probably main well leakage for your raw gas problem. The original intake would have kept both throttle bores completely isolated, make sure your new intake does the same. In other words, does your hi-rise have a passage between the left and right side of the plenum? This would cause a slight lean condition, off idle. I’ve never owned a timing light, you adjust your timing for the best performance. Generally speaking, you run the most timing possible without spark knock. This is usually best with older smog heads, Vortecs will always need less timing due to their superior combustion chambers.

 

Your gas stink may or may not be coming from the fuel pump and not the carb. Check it out before you blame the carb.
You need to get a timing light and track your advance curve. You do know about the little allen bolt under the carb that controls the air flap on the secondaries ?
I had a carb guru build a Qjet for a dirt car and the flap was adjusted wrong and caused a serious bog on restarts and it ran strong after it got going. We ran the same intake with a Qjet on lots of stock and hobby class cars when I raced dirt track.
It's a good intake , just a little heavy.

 

Crimp the vacuum line going to the secondary's to slow down the action. I've had real good results doing it this way..

 

Amen!


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The float bowls on them were notorious for leaking gas into the manifold. Speaking of manifolds, is it an open plenum or a 4-holer? What was the old one you took off?

I have a local shop that does Q-Jets for a reasonable price and they always come out mint. My rebuilds are hit and miss. Do you have a carb shop close by?

 

Best advice so far !

 

A comment on the leaking well plugs:

This was one of a few teething issues with the Q-Jet, which debuted in 1965. (So this discussion is non- H.A.M.B.-friendly - it becomes "history").

The early Q-Jets used a pressed-in well plug, which did leak. The early "fix" was epoxy covering the plugs, and a foam pad cut to fit the top side of the throttle body to attempt to hold the epoxy. As is easily predicted, the epoxy did not hold up in gasoline, and the leak continued.

In 1968, Rochester changed from the pressed-in plug to forming the body casting over the plugs. This virtually solved the leak; although if tested with high pressure, some will still leak. But for use, the 1968 and newer castings do not have a well plug issue.

To the OP: carburetors are calibrated by engineers. Yes, they can be re-calibrated by someone with experience. However, often that experience, if acquired without supervision (apprenticeship), is acquired at the expense of the carburetor (or other item being modified).

Check the second line in my signature block

Jon