Q-jet air horn leak fixes?

Backed the 2NABOT out of the garage today, and let it run at a high idle to warm it up for awhile, then went to work on the interior, etc...

Got to working under the hood, and noticed that there's fuel all down the front of the Q-jet, like the air horn is really loose, which it isn't. Gas is trying to collect on the manifold, right in front of the carb. Also some fuel on the top of the front of the air horn, right around the fuel pump rod and a small (3/8") press-fit plug beside the fuel pump rod, to the center. Not enough gas to pool and be a scary fire hazard, but no gas leak is good.

All it did was run at 1000-1200 rpm for maybe 15 minutes, no driving or sloshing about.

What gives? It gets dirty there over time, but I never noticed this much fuel leaking before.

If the air horn is warped, can I do the sandpaper-on-a-sheet-of-glass routine to get it flat again?

 

Question #2

Also, why would it leak there anyway, with no sloshing around? Isn't the fuel level below the gasket?

o No:

 

I think I'd start with a fresh gasket up top. While the top is off, take a straight edge and see if there is any obvious warping.

Be SURE to properly torque the screws down.....not too tight - proper sequence too.

 

Check float level!

 

If the 2 bolts up front that hold the carb down to the intake were overtightened at one time, your airhorn could be warped.

I had that problem on one of my old carbs and in order to sand the airhorn flat you would have to remove the 4 pressed in brass tubes from the airhorn first, I don't think that would be a good idea. You might be better off trying to use 2 gaskets to correct the leak first. Gasket sealer doesn't work on carbs either, it will only end up inside and cause problems.:bglasses:

Pray it's the float level.:grin:

 

Just a side note, you used to be able to get just the air horn gasket from NAPA without having to buy the whole carb kit. You just need to find a parts man who knows the books. You have to match up the gasket with the picture in book.:bglasses:

 

Should never have fuel leaking from there..

Perhaps the needle and seat has gotten some crud in it and is not sealing, thus allowing overfilling of the floatbowl.

I would replace the needle and seat, and filter. Clean out everything before installing new parts. Properly set float level. and reinstall airhorn with new gasket.

That should do it. o No:

 

I wouldn't think o No: the float level's too high, it starts fine, and ran like a champ last time I had it out and went driving around...but of course, I'll check it out. I wasn't sure about doubling up on the gaskets, if that would throw off some setting elsewhere, like the brass tubes, but I'll take a look at that as well.

That reminds me - What's the actual fuel level in the bowl to shoot for? I've run engines with the Rochester 2-bbl, you can take off the air horn, pour fuel into the bowl, and run the engine on the idle circuits with the carb opened up.

Can a Q-jet do the same? If so, the float-in-the-bowl design would let you see the actual fuel level in operation.

 

NAPA has a website that can be used to find a part number of something like that gasket. . Pretty just walk into the store and ask them if the have the part by number. It's www.napaautoparts.com

 

No, I don't think you can but I never tried that. If that worked, better hope you don't get a backfire!:shock:

 

Doubling up the top gaskets would throw off quite a few settings!!

I a new gasket won't cure the problem - the top is quite likely warped.

 

I wouldn't even try that on an engine that I thought would backfire, but you're right, and I do keep a good extinguisher real handy when doing any fuel-related work. Don't want to look like this guy! :af: I have nothing but respect for things that go 'boom'. (Learned that back in my Tanker days.)

If the airhorn is warped, and if it can't be straightened, I take it a new/reman carb is the answer. I really don't want to go that route, I've done a lot of work (fine tuning, smoothing internals, etc). I'm pretty sure I already know the answer, but is there a source for just a non-warped airhorn?

 

Local boneyard should have a good supply!!:Brow: :TU: Cheap too.

 

ebayyyyyyyyyyyyy....


I have bought about 6 qjets from ebay sellers...all under $25.

 

Figgered it Out!

Well, after working on the 2NABOT all saturday and last night, I've got the fuel leak stopped.

You won't believe this, but not only was the air horn warped, (WARPED about 1/16 to 1/8 gap in the middle),
:eek2: :eek2: :eek2:
the entire carb body was warped/crushed out of shape!
:eek2: :eek2: :eek2:

The carb is about 5 years old, a reman unit from AutoZone, and hasn't been driven much in the last 2 years while I worked on the interior. Now, I know better than to overtighten the airhorn. But from the looks of things, somewhere along the line somebody tightened it down to about 75-100 ft/lbs, and not only warped it, but crushed the front corners down 1/16-inch on each side! The airhorn and body kinda fit together and sealed for a couple of years, but I guess it caught up to me.

I really need to get some pics of this up on the board. Un believable.ou:

Curently, I've got an 800 cfm Q-jet from my '72 project 455 in the engine. Also went back to the original-type choke. Niiiiccce...
:TU: