I've rebuilt my q-jet but it keeps leaking arond the airhorn gasket. I've replaced the gasket twice but still leaks. I've heard that the airhorns can get warped. Is this true and would this cause my leak? Anything else?
The whole carb warps from the bolts that hold it to the intake. Try adjusting your flost down a little bit.
This always works for me>>> Use two air horn gaskets and coat them with heavy weight oil. this will make up for minor warpage.
Start with the center two screws, then tighten them like you would a wheel....corner to corner. Nice and snug is enough. You don't need to lean into it.
proper factory tightening sequence for the airhorn screws are first the two inside the primaries then the 2 behind them then the single front then the two long ones in the rear and last the two outer sides.
Great pic Adam, did you do that? Wonder how many guys have a Q-Jet with that problem and don't realize it? Dave B
Other than the way the carb looks, this is not generally a problem (but one that is often solved at great expense!). This, as mentioned, is caused by overtightening the two front carb to manifold bolts. The specified torque for these bolts is 9~12 pounds-feet. This is about the maximum amount of force that an 85 year old grandmother of weight less than 100 pounds could exert with a short box end wrench! However, Rochester knew that some ex-gorillas that were too all-knowing to use a torque wrench were going to tighten these things, so the engineers anticipated this issue in the design. When you have the airhorn removed, observe the location of the "sealing ridges" around the bowl. You will notice that the sealing ridges seal inside of the compartments containing the mounting bolts. These compartments are really "crush areas". If the sealing ridge is biting into the gasket all around the bowl, then other issues may be causing the leakage (defective float, defective fuel valve, etc.). Jon.
This is one of the many is my stash in the basement. None of the ones on my cars are like that. That's one of the more extreme ones I've seen. Thanks for the insight on the warpage issue, Jon:beeer
It almost seems like the gasket is soaking up the fuel and its seeping out through the gasket. I guess that would indicate a too high fuel level. I've already adjusted the float twice and its a new float. At least you guys have given me some ideas of what to look for. Now all I need is some time off work to look at it.
I've used the torque wrench and gone to 13 ft/lbs (as specified in my service manual) and that is way tight! I can watch the carb warp before it gets to 13! I always just snug them down--maybe 5 ft. lbs. Works just fine. I've also watched John Osborne do it, and taken one off that he installed, and he doesn't go anywhere near 9-12 ft. lbs. Just food for thought...
