Howdy,
I have a 1904 Holley 1bbl carb that has just been rebuilt, and it's leaking from the fuel bowl. I have tried different gaskets, and now even have 2 gaskets in there and tightened the screws down pretty good. The fuel bowl is GLASS, and the main body seems to be pretty straight - the original carb was also leaking(!) but it was deformed from the fuel bowl being overtightened over the years.
The fuel level in the bowl is about 2/3rds the way up. The truck starts and runs good, and I took it for a couple mile run, and got back and no leaks. An hour or so later, still no leaks, but then several hours later, gas on the exhaust manifold. Pretty good spot this a.m. The bowl is still about 1/2 full. It didn't seem to FILL UP after it was shut off and overflow, it seems like it's coming out of the bottom of the bowl/main body area, and again - I didn't notice any major deformation or problems in the bowl or carb body. The glass bowl seemed to fit pretty good, and I am using the metal spacer and "butterfly" washers/brackets with screws and lock washers.
I have tried different gaskets (including cork) and sealants (none of which are gas resistant that I have found so far)...
I just got the carb and disassembled it and soaked it and put a rebuild kit on it, and when it was first assembled and run, it was fine, no leaks, but after being SHUT OFF an sitting awhile, it starts leaking.
Is there a "break in" period on the carb gaskets - do they 'weep' for a few days and then swell up and quit, or ? I got some extra thick paper gasket material and it a SECOND layer (of it) on top of the original gasket (also paper) that came with the rebuild kit - so there are 2 gaskets in there now. I had tried glueing 2 together with 'aircraft sealant' ("gasoline resistant" - it wasn't), and also Permatex No. 2 (ditto), and even Marine 5200 sealant (I got smart and glued a gasket to a jar and then immersed it in gas a few days later for a test) - it dissolved too... what a mess...
The original carb was leaking the same way, but it was definately deformed. I changed the fuel pump (mechanical) about a year back, and don't see any fuel leaking from the line/fittings. The needle was replaced with the kit, and seems to be free, and clean...
Anyone have any thoughts or suggestions...?

Thanks!

 

What condition is the manifold in? Perhaps it's distorted or cracked, which can cause a leak...???

 

The manifold is the original. The carb/fuel bowl is several inches above it though. I'm sure not disputing it might be a factor, but don't understand how - maybe you can explain? Unless you mean that it might have a leak and be "blowing hot" on the fuel bowl, superheating it, boiling the fuel... but I don't think so, as when I turn the truck off, I pop the hood, and the fuel looks "normal" in the bowl, and it doesn't start leaking for awhile.
Anyway, if I am not not following you, let me know how you think the manifold might be affecting it, ok? I hadn't considered it too much...
The carb has the standard 3/4" gasket between it's base and the exhaust manifold, and the bowl sets up and over the lower part of the manifold, not right over the side of the engine.
Sure has me befuddled... Thanks for the info!

Red

 

Is it in fact leaking between the bowl and the carb body? maybe the leak is internal in the carb and then out the throttle plate shaft.

Can you actually see where its leaking?
Bobby

 

I have the same problem with a freshly rebuilt carb, so am reading with interest...

 

I had an IH Scout 4-lunger with the same carb and it leaked from every possible location. They are simply not a great carb design. Neither are the 94's for that matter. Cork is porous, only 1/8" thick Viton sheet has any hope of sealing and lasting on the fuel bowl. I'm not sure you can find any.

 

Thanks,
I haven't heard of "Viton sheet". Is it rubber/silicon? I haven't had any luck looking on the 'net for a source. Where would you suggest I find it? I have been to Autozone and Advanced Auto, Pep Boys, and O'Reilly's... and didn't see any there - but 3 of those places have all of their gasket materials behind the counter, and I just told them I wanted gasket material (I didn't specifically ask for "Viton").
Where have you seen (or bought) it?

Thanks,

Red

 

Viton is the premium grade of rubber (a synthetic) that withstands fuel best, without turning to jelly or swelling. I am not sure if it even can be made in a sheet, I think it may have to be molded. NAPA would be the only place I'd trust to have it, or a seal supply house, industrial supply, etc.


By the way, check to make sure the gas isn't leaking out around the idle mixture control screw. They have an O-ring and if it is shot, gas will slowly trickle out of it.

 

Here ya go;

http://www.mcmaster.com/

type in "viton sheet" in the search button

Bobby

 

Thanks both,
First of all, I don't think it's the idle set screw, it's around the back side, but a good thought. I don't remember it having an O-Ring on it at all.... hmmm. I guess it's on the idle screw itself, between the screw head and spring, or after the spring? I'll take a look.
Thanks for the info on Viton. I went to McMaster.com, and looked at what they have, but will do a little more research on which type would be best for a fuel application.
If anyone has any other possible ideas for a source of a leak, I'm all ears!

Thanks again!

 

Mcmaster Carr is amazing. And the cool thing is that you don't have to make a minimum order.

Keep us posted on what you find. I got a little 1brl on a 170 I6 in a 1965 Falcon that is weeping a bit but I havent had a chance to look at it yet so I'm curious about what you come up with

Bobby

 

Any solution to this carb problem yet? Are all mounting surfaces flat?

 

Hi,
No solution to the carb yet. All the surfaces are flat, and I have redone the gaskets (more than once). Friday afternoon, I tightened the screws down a little more, and I started it and ran it for 40 minutes or so - no leak. I came back an hour later, no leak. I drove it a couple of blocks away, to a friend's for dinner, and then back home a few hours later, and no leaks! The next morning, GAS GAS GAS. again.
I feel like I am chasing my tail (!) buying this and that gasket material. I've had 4 different people tell me that "this one" will work for sure (at the local auto parts store - but they don't know too much, usually!), and all failed. I am beginning to suspect that it's either a jet problem or the needle isn't seating, so tore it apart again this afternoon. I sure don't see anything obvious.
Is it possible that the needle isn't seating properly, or that there is a jet problem and that gas is 'syphoning' into the bowl after shutdown?
When I first rebuilt the carb, and started it, there were no leaks, and I shut it down, and it looked like the fuel bowl FILLED UP (full). Hours later, I noticed the level had dropped and gas leaking. I haven't noticed the fuel bowl filling up anymore, but it always leaks - regardless of one or two gaskets, or whatever type I've tried.
I set the float according to the rebuild kit, but at this point, I am questioning everything. Float, needle, jet?
OK, *if* it's not the gasket... what else could cause this? I don't think it's super-heated fuel after shutdown (percolation), and again, it doesn't seem to leak during operation - unless the fan is just dispersing it and it's not showing up... but I don't think so...

Thanks for any thoughts...!

 

It sounds like your fuel line to the carb and the fuel in the bowl are getting hot and the gas is expanding, and is able to push past the needle valve. I assume you are using a stock fuel pump? (mechanical) It may be absorbing heat too. There are all kinds of trick to keep the fuel lines cool; insulation (slip a split rubber fuel line over the steel line), route the lines away from the engine as much as possible. Use as little rubber line as possible. By all means keep the lines far from the exhaust. The ideal solution is a pressure relief but that requires a line back into the tank.

 

Not to insult you, but is the float set correctly? It could be filling too full and getting out a vent? There is gasket material at some auto parts stores that is fuel-rated.