The Stovebolt Site Forums The Shop Area Engine Shop Fenton 2 Carb Intake Issues

I'm currently installing a fenton dual carb intake on my truck with 2 carter YF carbs. The truck will run at a fast idle for less than 15 seconds and then stall out. Any ideas on what I've done wrong?

The last time I had that problem.I forgot to connect the pcv hose to the pcv
valve.One big vacuum leak.

Jimmy

Sorry, I'm new so this may be a stupid question. With the down draft tube, what PCV valve are you referring to?

No PCV on a road draft system.
I'm inclined to think timing. Especially if you do not have a vacuum advance on the dizzy. I have also seen where with duals, there isn't enough vacuum at the carb base (ported vacuum) to make the advance work properly, so many go to the fitting on the mnaifold instead. On mine, I don't have an advance, so I had to advance the base timing by 15 degrees to get it to run properly.

O'Kay,I went back and read your old posts.

I would go back and check the carbs. again.To be sure everything is clean inside and check float adjusted.

notajr88fan,

While there could be other problems, I would sure spend some time making sure the throttle linkage was 100%. Without any linkage installed, both carburetors need to be in the same position to each other.

If you back the idle screws out of both carburetors until the throttle plates are closed, that is a starting point. Reattach the linkage and start adjusting your idle, making sure you do exactly the same thing to both carburetors.

They need to be balanced in regards to their throttle position. This will get you started and may cure some of your problems.

Stuart

Try installing a thin card board gasket under one of the carbs to isolate it. Don't cut the center hole, make sure it's solid. Get one carb where it will idle and run, then do the other one the same way. If you set the idle speed the same on each one, it should be close with both running together. You will still need to tune once both are running so turn each screw the same on both units till you get it squared away. A Uni-syn ( http://www.speedwaymotors.com/Uni-Syn-Carb-Synchronizing-Tool,267.html ) would really help you.

Double check for vacuum leaks at the intake to head area and under each carb. If the engine was running before you started this, timing should be close enough to run now.

Whats it take to get it restarted?


Joe

I agree with Joe H. If each carb will run the engine by itself (factory setting for mixture, etc.) then you are half way there. I run a vacuum advance off my front carb, and it works fine. Though, I did advance my timing quite a bit over what I was running with a single carb. I think I ended up another 8 degrees past where I was.

Why do you think the timing needs to be advanced so far? I set mine higher up as well, but didn't think the carburetors had anything to do with it.

Joe

When I recently replaced my 235 exhaust manifold, I had a similar problem. It turned out that the intake wasn't fully seated because one of the alignment rings was slightly cocked. My leak was bad enough that I only got about 5 seconds of run if I pumped the accelerator pump 7-8 times.

regards,
Leon

I wonder if I have the same problem as Leon. Mine starts and dies. It doesn't look like there are any gasket leaks. When I do get it to finally catch and run it's OK so I don't know if one of my rings is cocked or not. I've got 21 in. of vacuum when I can keep it running.Didn't mean to hijack this thread.Is it necessary to run the rings? I put studs in the head for Int and Exh.

wes,

If you have 21 inches of vacuum, you most likely have no vacuum leak.

Joe, I set the timing further advanced, 'cause California Bill told me to. I ended up that far advanced, through road testing, you know, drive up a big hill and accel from 20mph, listen for knocks.

The vacuum gauge would be a handy tool for this project, seen guys work on this for a week only to discover a giant vacuum leak. I had a difficult time with my dual carbs due to crappy linkage and throttle plates not working exactly together. The vac gauge is the best tool for setting timing as that original timing mark will be way off with dual carbs, cam etc etc.

Sounds like vacuum to me too. I had trouble with this intake and a set of 2 bbls. The problem was with the gasket under the carbs. They weren't cut right. Made my own gaskets and now everything is good.

Well I finally got the engine started long enough to mess with the carbs. I am having an issue with fast idle and when the idle settles down it stalls out. Any suggestions?

Make sure you have a good fuel pump and fuel line, old ones can restrict flow. Also you should make sure the carbs are set up properly, floats set at correct level etc.
Also as I mentioned, get a vacuum gauge, connect to your intake manifold and set your mixture, timing etc to highest vacuum, it's a great tool and inexpensive.

Be sure to look down the bore of the carbs and get the linkage set so the throttle plates open exactly together, then you can set mixture etc.

Sounds like you are fighting a loosing battle. Take my advice and block one carb off till you get the first one running. Then do the second one. You have doubled the problems plus some by adding a new intake. Just one change at a time can drive you nuts, you have three or four going at once. Rebuilt carbs are a problem all by them self!

Vacuum leaks can cause all kinds of problems, and since yours won't idle below a fast idle, I would bet you have one or more leaks.

Even though you have 21", its not at an idle so it doesn't count. Until you can get it down to 600 or 650 steady rpm, the gauge won't tell you much. Even a small leak will cause a big problem with dual or triple carbs, you all ready have 1/2 the air flow through each one so cut that down with a leak and you could be in 1/4 to 1/8 th of the air flow the carb was designed for.

If you can get it started again, leave it at the rpm it wants to run at and spray WD-40 or Carb cleaner around the bases and gaskets, if it rev's up you found your leak.

Joe