The Stovebolt Site Forums The Shop Area Engine Shop Duel Carter W-1's dieing at idle

The engine will idle just fine for several minutes, most of the time. It's random as to when it will die. At first it would die with no stumble or anything. I noticed wet fuel at the float boat lid during my inspection so I thought the carb was flooding causing a rich condition during idle and would kill the engine. I could restart the engine if I gave it some throttle while starting it.

I saw the fuel so I took off the top of the float bowl and adjusted the float on both carbs. Now it does seem to run better but it will still die, however, it will stumble and rpms will dip before dying. Am I on the right track here or should I look for something else? I know I don't want to adjust the floats too low.

Langdon HEI, 235 c.i., Fenton intake w/ Carter W1's.

The first two steps are the same as with a single carburetor:

(1) compression test

If good compression then

(2) complete ignition check

If both compression and ignition are good then skip to the synchronization section of the following link:

http://www.thecarburetorshop.com/Dual1barrelcarbs.htm

Jon.

Compression test done.....with not so good results.

#1-136
#2-120
#3-145
#4-95, W/oil 105
#5-140
#6-135

So not bad except for #4. Adding oil didn't seem to do much, would that mean its a valve problem? Or do I have to take it all apart to find out?

Could be valve not sealing or partial open. Could worn cylinder or rings not sealing. How many miles on engine and have you been driving it?

How does it run with one carburetor?

When were the valves last adjusted?

Joe

Miles since rebuild unknown, my odometer has been broken for some time. Engine was rebuilt in 2006. I have driven the truck off and on because I would change out the intake/carb setup or swap something else.

I adjusted the valves right before the compression test yesterday. They are hydraulic. Some of the lifters would be squishing, others were rock hard and had no give.

Engine pulls hard on acceleration, revs up good with only one carb working.

When is the last time you replaced the fuel filter? Your description sounds like it is starved out of gas and stalls.

I would drive it around some and recheck #4 cylinder when hot and right after I knew it was running decent. A low compression engine doesn't create enough air flow at idle, thus starving the engine of fuel. Yours should be OK with just one a little low.

How does the exhaust smell? and how sooty is the tail pipe?

Can you change idle quality with the idle adjustment screws?

And finally, have you synchronized both carbs to each other? that includes linkage, idle speed, and idle adjustment.

Joe

Update- I have done more compression tests, numbers the same. I bought a leak down tester and it shows alot of leakage on #4. My old school country neighbor came over and had me pull off spark plug wires while it was running. Cylinders #1-#3, when pulled, made a difference in the idle. #4-#6 made little to no difference when the wires were removed. The wires are carrying spark, shocked the hell out of myself, and my neighbor. After being tazed in the police academy, it brought back memories..... I haven't checked the plugs yet, but with them being new, with Langdon's HEI I just installed, I'm fearing something deeper will be the problem.

bump

Check valve adjustment next, even a very slight open valve will loose compression. Since you will have the valve cover off, grab each of the valves & springs and see if any thing wiggles or moves. A worn valve guide can cause problems. You might also try twisting the valves on the low compression cylinders, they could have carbon build up on them. Twisting and turning my break it loose.

Joe

Thanks Joe H, I'll give that a try. But, I don't understand why #'s 5-6, that have good compression, do not effect the idle when the spark plug wires are removed. I'm afraid I have deeper gremlins.

In the future, you may be able to avoid being "tased' by just using a long screw-driver to short out the plugs momentarily, to test whether it affects the idle. If you've got heavy-duty plug boots, that won't work. Just an idea.

Here's another: Got a vacuum guage? a vacuum leak in the right spot will defeat the charge getting to the cylinder, rendering that cylinder useless, even though it's got good compression. Try spraying WD-40 around the intake manifold, around the carb. throttle shafts, etc. and listen for a change in engine speed. Does the truck have vacuum wipers? Try disconnecting that line and plugging it, see if it makes a difference. Also check the vac. advance line carefully.

Just a thought.

Keep at it, you'll figure it out eventually.

-Michael

in my humble opinion, it sounds to me like it could be a couple of things. first get dummy spark plug and check for good blue spark. then check timing. if you dont have a timing lite, bring up #1 cylinder and check where rotor is. it should be slightly before where number 1 plug wire is located. if all that is good? check vacumm leak by closing both chokes if so equipt. if not, turn idle up on both carbs until it runs. turn them down until it wants to quit. take rag and cover top of each carb slightly at a time. if idle goes up? you are running too lean. another way, spray carb cleaner around base of both carbs, spray intake gasket area. spray small bursts down thru carbs. ill bet you got a problem with ignition system somewhere. did you put dual carb systemon yourself? did it always do this? did it ever idle fine? if the answer is yes to all those? you need to backtrack

You can also try swapping the cabs front to back. You say 5 and 6 didn't change much with plug wires pulled, this leads me to believe the back half of the engine is lean. The way the firing order goes, 142635, it's unlikely the distributor is jumping number 6 and 5 and still have 3 working.

Try closing the choke on the rear carb or both of them.

If the engine ran before the swap, it still should run, valves and such don't go bad just setting. On the other hand, if it ran marginally before, the duel setup will just make it worse.

Joe