Fuel leak at fuel bowls

-
Evan Dutch

Evan Dutch

Well-Known Member
Joined
May 11, 2016
Messages
846
Reaction score
291
Location
North Carolina
I recently rebuilt a quickfuel 580 4 barrel carb for my 318. Yesterday I installed the carb and started the engine. It runs great, but after I shut it off and checked for leaks I noticed a small amount of gas where the fuel inlet fittings screw into the bowls. The inlet fittings are AN style, I installed them with new white nylon washers supplied in the rebuild kit, I screwed them in almost all the way by hand and then snugged them up with a wrench. Any idea of why they would still leak?

Thanks.
 
Make sure the gasket didn't slide while tightening? loosen it and take a look then retighten.
 
Crack in the fuel bowl where the fitting goes in?????
 
Use a paper towel or blue paper shop cloth to be sure the leak is at the inlet.
Slip it around the fuel bowls to check there too.

The nylon washers are acceptable but change them out when you can.
You can try snugging them up some more.
When the nylon gets hot enough it will begin to soften and the torque is lost. It takes an awful lot of heat in the engine for the carb itself to get that warm, but I've had it happen.:eek: :BangHead:
 
Mattax said:
Use a paper towel or blue paper shop cloth to be sure the leak is at the inlet.
Slip it around the fuel bowls to check there too.

The nylon washers are acceptable but change them out when you can.
You can try snugging them up some more.
When the nylon gets hot enough it will begin to soften and the torque is lost. It takes an awful lot of heat in the engine for the carb itself to get that warm, but I've had it happen.:eek: :BangHead:
Click to expand...

What should I replace the nylon washers with?
 
Evan Dutch said:
What should I replace the nylon washers with?
Click to expand...
The black aluminum ones from Holley.
Damaged nylon on left and new Holley alumunim on right.
upload_2019-1-23_20-59-43.png

The ones from BLP or Quick Fuel which are probably made of Interface MP-15 gasket material are probably Ok too.
 
Let me just mention that it was a hot July afternoon and had been driving mountains and then interstate for over three hours and then got stuck crawling in Friday traffic around Albany for a half hour or more. It was when I pulled off and was fueling up that I opened the hood to let things cool and saw the large pools of fuel in on the intake. :eek:
I tried loosening and retightening a couple times. but it wasn't until it cooled down enough - about a half hour later - that I could tighten it effectively. Not fun.
But it never leaked before or after. Of course I did replace them when I had a chance. The one pictured above wasn't going to seal much longer!
 
The Holley gaskets are metal with some kind of plastic coating. They are the only ones that seal correctly, far as I know.
 
I have had great success with nylon gaskets, you just can't over tighten them they will fail. I even used the clear plastic rubber nylon what ever they were made out of metering block gaskets they made back in the 80's, I think sold by Mr Gasket co. they were the best could take your carb apart 50 times and the still sealed and came apart
 
You must log in or register to reply here.
-

Back
Top