Hi All,

I'm recently experiencing an issue with my new Holley Truck Avenger 670 CFM carb. The only recent changes I've done is set the curb idle mixture screws (using a vacuum gauge) and swapped out the stock heated carb spacer for non heated carb spacer and new gaskets.

Vehicle:
1969 F250 4x4 with FE360

Symptoms and observations:
The fuel pump is running a constant 7 PSI
The leaking doesn't occur until after the engine has been shut off
This didn't start until recently after the changes above had been done
Leaking starts somewhere around 1-2 hours after being shut off
Fuel is leaking from the vacuum operated secondary lever (underside of the secondary housing)
Little bit of leak near the throttle mechanism on the drivers side

I'm not sure what can be doing this. The only thing I can think of is high fuel pressure? I've purchased a Holley Fuel pressure regulator, but I haven't had a chance to install it yet.

Any ideas if this is the cause? If not, what else? There have been no recent backfires etc...

 

Fuel level to high most likely on the rear float, check both reset as needed.
I'd drop the fuel psi down to 5-6 and report back here if it's fixed or not..
Orich

 

Yup, seems it is getting a touch of heat and causing the fuel to boil over and leak out the throttle shaft. Fuel pressure running will have little effect.

Drop the fuel level maybe a 1/2 turn on the nut and see if that helps. If not, need to get some kind of insulation between carb and intake. Don't know what you used, but if it is metal, that is not a good choice.

 

2X above. I'd put a thick carb gasket under it to insulate heat. Like what was Ford part number E5HZ9C477B. Fit zillions of Ford vehicles from Medium Duty trucks down to Mustangs with 4V. For a application you can tell your local parts store 1985 F150 with a 351W 4V. Holley 670's have the same 1 9/16" bore as a 600. Which is what Ford used.

 

A one-inch phenolic spacer staves off heat conduction and convection plus will help low end torque. Consider Edelbrock PN 8711 for about $30.

 

2X Hio. If ya do this and all who might have an automatic tranny,ya might consider Holley part number 20-41. It's an extension for the kick down lever so it can reach the carb better with that spacer under it.

 

Hi All,

I put on a holley fuel pressure regulator and finished off the gas line with some braided nylon hoses and russell connections - Looks Great and the fuel pressure is hanging steady at 5.5psi! Additionally I put on a 1 inch thick composite spacer (All Start performance - Image link below) But I still have a problem with gas flowing out on to the intake manifold.

Last night I added the new spacer and gaskets, then today I ran the engine for about 10 minutes before shutting it off. After returning to look under the hood and hour or so later I see a small puddle building up on the manifold. Additionally the little arm under the vacuum secondary has a bit of fuel on it. I'm stumped


http://static.summitracing.com/globa...F-ALL25981.jpg

 

Did you check the fuel levels??
Orich

 

Hey Orich,

Yes, fuel level was checked. No smoking gun there

Thanks!
Jason

 

Where did you get this carb? and was it like this since you got it?
a lot of holley's junk ends back up on ebay an resold ..
orich

 

Hey Orich,

The carb came from a local retailer (Baxter Auto Parts), but I think I have something i've found in regards to this. Over the past week I haven't run the truck at all. The other night I went back and verified there was no gas sitting on the manifold. The following day temps reached in the low 90s. I checked the gas cap to see what kind of pressure was in the tank and man there was a lot of pressure. Additionally I checked the manifold and there was standing gas next to the carb again. All the times I've been seeing this it was generally high temp days so what I suspect is there may be too much pressure building up in the gas tank. The gas cap that is on there has a vacuum valave meaning if the tank develops suction it will help equalize the pressure, but the same isn't true for the opposite direction therefore there is a huge amount of pressure that is building up and I think it may be enough to over power the carb. The gas tank was purchased from LMC but it seems very close to the original. I wonder if the gas cap isn't the appropriate one?

 

Have you tried tightening the end float bowels a little. My 71 f250 4wd truck also builds up a lot of tank pressure. My gas psi is setup 6psi and don't have any problems.

Back a number of yrs ago Holley had carpy gaskets and orings on the cross over tube that would sometimes leak. Then they changed to the blue gaskets reusable ones.
And used a thimble type open end replacement for the oring tude ON THE OUTTER transfer tubes that is.

Try leaving the cap loosen some and see what happens.
Orich

 

I'd get a new "vented" gas cap.

 

Mind is vented for high pressure release by pass if it gets to high.

Yea but if needle seat fails then it will flood the carb.
And have not happen in my case.

I once did have some flooding issues on another Holley yrs ago with rear flooding where, I had run the lower float level to correct the problem.

I always re-set the floats while the engine it running just have to be careful not to cause a fire. Keep some rags handy to suck up any spilled gas.

If your unsure of doing it this way don't do it then.
But this how we all learn to do stuff by going outside the Box of safety rules.

orich

 

Thanks guys. The gas cap that is on it is allegedly a vented gas cap (Image below). I cut the vent off it and over the past few days, even after running the truck I no longer have fuel leaking out