Idle Mixture Screws Leaking

[gmc396]

I've got a '68 GMC C2500 with a 396 and Rochester GMV carb and 4-speed. I was fine tuning the idle mixture screws and noticed some gas on the intake manifold after I drove the truck. It looks like the idle mixture screws are leaking a bit. Is there a small donut gasket in the hole where the mixture screws go? Any suggestions on how to stop the leak? I finally got the truck set up and would rather not pull the carb. Thanks for your help.

[Coley]

I think you might find that the leak is coming from the separation between the lower throttle body plate and the upper main carb body....which is probably the join gasket.
Removing the carb and regasketing it is not overly difficult....its kind of interesting actually. Its also a very good time to give the carb a serious cleaning.
....just my two bits.

All Good
Coley

[68is4me]

Probably the well plugs are leaking. Very common problem. Get a rebuild kit, and put epoxy on the plugs. The plugs are the one circled.

[gmc396]

I've had the truck for several years and had no leak in this area until I adjusted the idle mixture screws.

[LONGHORN1962]

A carb repair kit will come with new seals for the idle screws.

[gmc396]

Any recommendation on a good rebuild kit?

[LONGHORN1962]

I've been out of the auto parts business for a few years. Hygrade made one of the better ones. If you have a NAPA store they should have a quality kit.

[geezer#99]

Idle mix screws don't leak gas!
Unless your carb is flooding a bit.
Could have been flooding a bit before you touched them.

[gmc396]

It could be flooding a bit as it seems to run rich at idle. I assume that would be the float adjustment.

[geezer#99]

Possibly!
Or a float that's sinking a bit.
Or crap in the needle/seat.

Or idling on the power circuit.
What's your idle rpm?
What's your initial timing?
Where's your vac advance hooked too?

[gmc396]

Idle is about 650. I had it idling at spec 550 but liked it better a bit faster. timing is 4 degrees. Dist. hooked to vacuum port at carb front on driver's side.

[geezer#99]

Try bumping your timing up to 14. Then turn your idle down to 650 and adjust your mix screws.