Q-jet help please

[Mark Trent]

I have two issues with my qudra jet:

1. the replacement accelerator pump that I put in it from a rebuild kit, appears to be to big (the black rubber part of it). It won't spring back up all of the way from the bore. I put the old one back in and it goes all the way up, although I think it's actually too worn, or loose.

2. The airhorn gasket (the top gasket) keeps getting wet on the outside. I have all of the airhorn screws tightened well and I used a spiral pattern from the middle - out, to tighten them in several stages. Is this a problem with the power piston or float? It started doing this before I rebuilt it and is still doing it.

Thanks - Mark




scroll to the bottom to see pics here

[William C.]

Re: Q-jet help please

As a first guess, I would replace the float. The floats over time tend to absorb gasoline and "sink" Based on the symptoms that is likley where the problem arises.

[Joe L.]

Re: Q-jet help please

Mark-----

1) The situation that you describe with the accelerator pump is common with a new pump piston. It should work fine, though, when it is installed and the carbiretor "buttoned up". You guessed it with the old one------it's worn in (and likely worn out)---that's why it appears to work they way you "would expect one to work";

2) The air horn gaskets often "wick" a litle fuel. However, yours appears excessive to me. At this rate of wicking, you'll get "dripping" at some point. The gasket should NEVER, EVER cause "dripping". You may have a warped air horn (fairly common problem) or just an inferior gasket with the kit. An excessively high float level could also be a factor, but I really doubt it.

By the way, the carb-to-maifold gasket that's correct is the one that looks just like the one that you removed from the engine. That's the correct gasket for a non EEC 1970. The other gasket (on the right in the photo) is for 1968-69 applications.

[Dennis D.]

Re: Q-jet help please

Can't remember right now, Joe will chime in, but I don't remember if the 70 intake has the crossover between the front bores.

Anyway, excessive float hight will cause a wet airhorn gasket,(easy fix)
Warpped airhorn also.(not so easy)

[Joe L.]

Re: Q-jet help please

Mark and Bill------

Yes, I agree 100%. If you have not replaced the float, you should do so. These things should ALWAYS be replaced when a Q-Jet is being rebuilt. I don't know why they don't include them with the rebuild kit. I suppose it's because, then, the kits would get a lot more expensive. Anyway, the float you need is GM #7037705. It's available from Delco dealers, too.

[Joe L.]

Re: Q-jet help please

Dennis----

The 1970 Q-Jet intake did not have the "carb preheat groove" (forward of the primary bores). Mercifully and wisely, GM dropped this "feature" after the 1969 model year from all Q-Jet manifolds.

[Mark Trent]

Re: Q-jet help please

Thanks for the quick replies! I will go get a new float tomorrow. I'm glad there are knowledgable guys like you all here willing to help out the novices like me! Thanks again - Mark

[Terry F.]

Re: Q-jet help please

Strongly agree with Bill. I had the same problem on a Quad once. Would not idle worth beans. Replaced that float and my 396 was very happy. I would be happier if I still had it. Terry