Carburetor Quirk

I have a Holley 390 on my 240 via an Offenhouser DP6019 (Dual Plane) intake. After putting a refresh kit in the carb I have resolved a handful of issues I was having. I bought it "Refurbished" but found the secondary float was cracked, the power valve was malfunctioning, and the secondary spring was way too stiff.

My chronic issue is that when I shut it off a fuel smell emanates from the doghouse and all of the fuel drains out of the fuel filter, I'm guessing back towards the pump but thought there was a check valve in there to prevent that. If it sits for more than 10 minutes I need to crank it over a bit for it to deliver fuel again. I usually end up pumping the accelerator about 4 times to prime it. The funny thing is if the van sits for a few weeks this symptom goes away for the first couple of drives.

All fuel lines are new including the pump and there are no leaks that I can see. I measured the fuel pressure and it is within range for the Holley (5-7 PSI).

Is the carb getting too hot and fuel is boiling out? I don't have a spacer on it right now but I have a 1/2" phenolic I can put on. Any thoughts?

I have no experience with this carburetor/engine combo, but your thoughts regarding the spacer seem right on the money, and can't hurt if there is no clearance issue to the doghouse. Try it.

Of course, an electric fuel pump would resolve the lack of fuel on startup, but not the odor (percolation?) problem.

Brian.. Mr smith is right , put the spacer or a thick 3/8 gasket insulator with the plastic things around the bolt holes so you don't over tighten it, they do work, I have had that problem. I went to a street demon that has a composit center and it keeps the fuel about 20dg. cooler...:BEER:..jh

I do have clearance for up to 1/2" of spacer. I had a 1" spacer on it before and had similar issues but now that the carb internals are in order it might be different. I also had clearance issues with the 1" so I had to take it out.

I should have time to get it on this weekend, I have to change the studs out for longer ones. Hopefully I'll be :3g:

Build a stainless steel heat shield for the carb and install it between two 1/2 " phenolic spacers. The heat shield might help keep the exhaust heat from warming the carb so much. Make the shield as big as will fit. Have it extend to the edge of the doghouse side and have it extend front and back by several inches past the float bowls.

The float bowls should maintain enough fuel between starts to start the engine and keep it running until the mechanical pump catches up.

I also have a nice Mallory electric pump if you want to try that. It doesn't require a regulator and is preset to 7psi.

I finally had a few hours on Sunday and got the spacer installed. There is a definite improvement in starting after its warm. I have also been running without my splash pan which acts as a plenum for air coming into the doghouse. I installed that on Sunday as well.

The issue persists but it is getting better. A lot of hot air does get trapped in the doghouse especially at stop lights. Perhaps the Holly is more sensitive to the heat than the stock Autolite 1100?

Pat, I will look into building a heat shield system for the carb. There are a couple other early vans with this carb setup out there and they have not reported the same issue.

Brian, Maybe you need a stainless wood-stove flue going out of the dog house up through the roof to exhaust the heat.

Where is Photoshop when you need it...

:D

I have one more idea to throw out. Maybe adding some heat wrap to the header will help lower doghouse temps.

http://www.amazon.com/DEI-010121-Bla...s=exhaust+wrap

This assumes you have a header. I don't remember at this point.

Any room to install an air intake hose routed to some location far enough from the engine to always be sucking cold, fresh air?

You would need to find a plenum like the one below that fits your carb.

Quote:

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Originally Posted by Luva65wagon

Where is Photoshop when you need it...

:D

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Hmmmmmm.....

Nice Kenny, I might as well put room for a hot plate too...

Roger, I already have the K&N Plenum below with the Apollo filter on it but I do not have it plumbed out of the Doghouse. I have the parts I need to do so but its lower on my to do list right now.

http://www.knfilters.com/images/l/85-8921.jpg