Holley 1920 carb issues!

[Al Bundy]

Hi,I hope you guys can help me out here. I had the Holley 1920 1bbl carb on my 70 dart professionaly rebuilt a little over three months ago. The car idles and runs fine however I am having hot starting issues. If I run the car and shut it off and then start it back up one or two minutes later,it will fire right up at the bump of the key,if it sit for over five minutes it is hard to start and I have to depress the gas pedal and hold it part way while I crank it until it fires up and then it will idle rough for about 5 seconds and then smooth out and run fine again.

Recently a couple of times when I went under hood later to check oil,etc. I would notice a couple drops of fuel on the intake below the fuel bowl. checked the screws and tightened them,then didn't see any other drops,then today I was checking the oil again and noticed a few drops on the underside of the fuel bowl. I took the air cleaner off and it looked like maybe the fuel may have dripped from near the little yellow button (anti-percolation valve?) on the top of the carb, I tightened the screws gently and drove it again and didn't see any leaks anywhere,but it is still hard to start when its warm and sits more than a few minutes.Does this sound like a sticky float issue?

Unfortunately for me the warranty on the carb rebuild expired 4 days ago so it looks like I will have to figure this out myself,unless the guy at the shop decides to be nice about it.

 

[JoeSBP]

check your fuel line routing. keep it well clear of the header

 

[Al Bundy]

A clear inline filter was installed before the carb and I was careful to keep the fuel hose away from the exhaust manifold.
The car always starts right up with a bump of the key when its cold,even if it sits overnight. I don't even have to pump the gas once. Its only hard to start once its warm and sits for more than 5 minutes or so.

 

[mvh]

A heat-related issue sounds like vapor lock. Slanties often have a problem with the fuel line absorbing heat where the metal line wraps around the front of the block, but they can also have a problem with heat soak to the carb from the manifold. How thick is the carb base gasket?

 

[nm9stheham]

The hard starting is likely too hot a carb or gas line. The newer gasolines have a lot higher volitility, so they boil more easily and turn to vapor in the carb or lines when the pump pressure is gone. As mentioned, the a thicker carb gasket may help, and keeping the lines cooler. Also, if the fuel pump's output check valve or the needle valve in the carb are leaky, then the pressure will bleed off and the fuel will boil more easily. A good fuel pump and needle should hold good pressure to the carb input for 30 minutes or more, and that should help some.

Also, see if you can find non-ethanol fuel and see if that helps. Alcohol boils more easily.

If the 'yellow button' is on a lever on top of the bowl, then that is the bowl vent area, and fuel should not come out of there. If so, then the needle is not seating well and fuel is coming out of the vent. Take out the needle and seat and clean them. Have a pix of the 'yellow button'?

 

[sgaugian]

Big issue that can cause all kinds of problems is fuel pressure from the mechanical pump. I worked with carb rebuilder that specs max 3 lbs pressure. I checked mine and it hit 7-9 lbs. Put holley regulator on it set at 3 lbs and all the problems went away and it starts first key turn everytime. The mechanical pumps will drive you crazy if you don't control them. I know this because I had my carb rebuilt also and got tired of the constant problems. If you want to seriously fix the problem, just get a fuel pressure gauge from local parts store and see for yourself.

 

[nm9stheham]

I would not be surprised if a lot of the newer made pumps are not well manufactured for pressure. A check of fuel pressure is always a smart thing to do but almost always overlooked....

 

[Al Bundy]

Thanks for all the advice. I didn't realize the fuel pumps made for these cars wouldn't be putting out the correct pressure for the carburetors used on our darts. I will have to stop by the auto parts store and pick up a gauge. So three pounds is correct for this carb then?

I do have a thicker gasket too,when I installed the carburetor I reused the original since it was in perfect condition.Guess I should go in an change that out too.

 

[sgaugian]

40 plus years and leaded gas which was harder to pump was how it was done back then. I can just tell you what I was told and it proved itself to me. My rebuilder uses 3 lbs max for all the units 2 bl or 4bl no difference they were all made and tested using same specs.