Carb issues with a new Holley 94

[yahbut]

Good day everyone
I have been lurking around the ford barn for a number of months and like what I see. I have a 1946 Ford Coupe that is pretty much original with stock flathead V8. The car was pretty much completely restored when I purchased it. I have had fuel issues with it and have removed and cleaned fuel tank, have electric fuel pump and new lines and filters. I put in a carb kit and float and still wasn't pleased with how it ran. So I purchased a new Holley 94. Made in USA purchased at George Moirs in Canada and its from Dennis Carpenter in the USA. The car now runs pretty decent but I am having trouble with the idle. The engine idles right down when I come to a stop....so low that it almost stalls. Now when you start it up it idles around 700 rpm and when you rev it up and let off the throttle it idles right down to where it barely runs. It does the same thing once warmed up. You can rev it up a number of times and each time it idles down to almost a stall. Then after a few times doing this it goes back to idling at the right rpm. Then you rev it up again and it drops to almost a stall. I have played around with the idle adjustment screws with no luck. Screws are out about 1 1/4 to 1 1/2 turns..... about where they where when I first installed the carp.......
I figured all my problems would be solved once I installed the new carb. it has new spark plugs and wires, complete new fuel system. I also checked throttle linkage for any binding etc. Any help would be greatly appreciated. Thank you

[George/Maine]

You should look at throudle plates see if they are loose

[scicala]

Did you try adjusting the speed screw ? You only mentioned the mixture screws which aren't really for changing the speed, but for trimming the mixture for smoothness.
Besides that, it sounds like the throttle lever is not returning to the same spot every time you return to idle.

Check to make sure the return spring is doing it's job, or for a loose peen where the throttle lever attaches to the throttle shaft.

Also could be loose throttle plates as George/Maine mentioned, although would be unusual.

Sal

[Kahuna]

George and Sal have good hints
Might also try tuning with a vacuum gauge to see if idle adj srews are actually working

[yahbut]

Yes I have the idle set at about 700rpms. If I set the idle say at 900rpm or higher ( which is way to high)it does not idle down to almost a stall when I step on the accelerator and then let off, it stays at 900 rpm. In my first post I mentioned that when I let off the accelerator it idles down to almost a stall and takes reving it up a bit a number of times before it gets back to a normal idle. I was just out again and tried it and was able to get it to return to regular idle speed by just slowly increasing rpms a couple time. I tried setting the carb again....I had mixture screws out about 1 1/2 turns. I cranked idle back so it was idling really slow and tried adjusting mixture screws. One screw I was able to turn in all the way and did not stall engine or really changed idle at all. This is a brand new carb and I talked to the company I bought it from and they said they've never had a problem with these carbs right out of the box. I see nothing wrong with the linkage throttle shafts etc. I am going to try tuning with vacuum gauge to see what happens.

[Frank Miller]

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A long shot but is the timing retarding properly when you isle down?

[JSeery]

"I cranked idle back so it was idling really slow and tried adjusting mixture screws. One screw I was able to turn in all the way and did not stall engine or really changed idle at all."

Well, I would think there is a problem of fuel is leaking somewhere if shutting the idle screw off does nothing.

[Bassman/NZ]

If one screw is not making any difference, you have a blockage in one of the idling passages. As far as idle speed goes, I had similar problem, installed a spring from the accelerator arm on the carb to the generator so it pulls it back harder and lands in the same spot every time. Worked for me.

[scicala]

Are you sure the new carburetor was made in the USA ? Or just maybe sold in the USA. If it's one of the Chinese knock offs it's hard to believe they said they never heard of problems with them. Maybe your's is the only one they sold.

Sal

[Big Red 51]

I saw Carpenter actually making and testing each 94 they made on a flathead during the Charlotte meet in June while going thru their shop. If it actually came from their manufacturing, you should be good to go. One guy at the meet had a bad carb and took a DC 94 and put it on and it ran good.
Don

[37 Cab]

Make sure your linkage is not binding a little and the return spring is doing it`s job.

[yahbut]

Thanks everyone for your replies. Yes its definitely a Dennis Carpenter carb. There may have been a blockage in one of the idling passages. I removed the screw and lightly took air hose to it. Now I can get some response when adjusting both idle screws. Its still doing the same thing....idling right down to where it barely runs and then slowly over time idles up. This time i set the idle using a vacuum gauge...no change.
I am also finding that after car has been run for a long time and when the car is idling the rpm surge s up and down a lot. I am thinking that Frank Miller may be right about timing not retarding properly. Well now check that out.

[Mike in AZ]

welcome to the 'Barn...got pics of your coupe?....good luck on getting your car running smoothly so you can enjoy it....Mike

[yahbut]

Thanks Mike. Yes I have some pics posted on my profile. Its been very frustrating trying to solve this issue. Would be nice if there was someone in this city that I could take it to that knows something about flat heads.

[George/Maine]

I had to change the engine in my 47 and I bent the linkage on fire wall.
When I went to put the linkage on carb the rod was to short. I made a new one longer by putting 2 together. So if you take a measurement from fire wall to rod closest to fire wall .Now remove link from carb and see if you have less clearance to fire wall.
Not a Toyota check the carpet for binding. There are springs in linkage could be broken.

[koates]

Hi there, A proven method for fault finding is to connect a vacuum gauge to the intake manifold. Look up a vacuum chart for fault finding and reading guidelines. There is a possibility you have a vacuum leak somewhere on the intake and it may vary in intensity with engine cold and hot. Check all intake manifold bolts and other intake manifold fittings for leaks. Good luck, Regards, Kevin.

[satelite]

I would also suspect a vacuum leak.

[denns1989]

Agreed on the vacuum leak... similiar issue with my flathead this spring, changed the intake gasket & all is well, no more idle or weird acceleration issues :-)

[41LjH]

I hope some of this helps..

1.Check the fuel filters you installed they may be partially clogged.. I haven't had much luck cleaning fuel tanks.
2. Check the timing and if you have a loadmatic distributor make sure the vacuum lines are connected correctly.
3.Check the fuel pressure on the electric fuel pump. It may be too high.
Even though the carb is new the float level may be incorrect.
It sounds like the engine is flooding.

[yahbut]

Well I tried the propane test and could not find any leaks. I install two new fuel filters, one before the electric fuel pump and one before the carb, when I install new carb as well as new fuel lines and had fuel tank cleaned and sealed. I wondered about fuel pressure cuz I do have electric fuel pump. The old carb was doing the same thing as this one only acceleration was bad and hard starting and ran rich even after a carb kit. When I bought the car it just had electric fuel pump so I thought possibly too much pressure and was causing these issues. So I put the rod back in the stock fuel pump, hooked it up and had electric fuel pump running through stock fuel pump. I had the electric fuel pump on an on/off switch and only used electric when car sat for awhile for better starting. Anyway after all this work the car didnt run any better. Then just before I bought the new carb I noticed fuel leaking out of gasket on stock fuel pump so I said screw it. When I put new carb on I bypassed stock fuel pump again.
I had the top off the old carb at least a dozen times setting the float...infact I almost had the slot wore out on screws. Thats why I finally bought the new carb. The new Denis Carpenter carbs are all run and tested before being sold.....I hear ya about even though its new it still might need float set......I just dont want to get started with that cuz id hate to wear the screw slots out on the new carb