Fuel systems kicking my butt - now carb leaking

[AR67GTX]

I’m beginning to think this Hemi may never see the road again. Last time I started it, one of those plastic fuel filters ruptured and sent gas everywhere. After replacing those and finishing up some other work, I tried to fire it up again today - only to have the front carb leak all over. Thinking maybe a float had hung, I carefully removed the carb and set it on my bench and removed the top. The floats were hanging OK but any jiggling could have loosened them. Fuel levels in the bowls were not high but the gasket was wet and fuel seemed to be coming out the shafts and various bleeds and every where under the cover.

Then I noticed the AFB secondary air valve wells had fuel in them as well as other places the top gasket should seal.

The cover screws were snug but not especially tight at all. I just rebuilt these carbs a couple months ago so all new gaskets, needle/seat, accelerator pump, etc in them. They were not leaking before rebuilding. I can’t see anything else out of place so all I can figure was the top was not tight enough to seal. The seats are tight and gaskets in place. Needles look sharp and clean. This is the front carb and since the engine was running on choke and fast idle, the front carb was just idling. Once the fuel bowls were filled to set level (and not flooding) and the needles seated where could fuel leak from under the top cover and end up everywhere????

I guess I’ll put it back together and make sure the cover is down tight and see what happens. If anyone has any ideas on this please share them.

 

[furyus]

I had this happen to me. No matter what I did, it still leaked. I gave up, and put a Holley on it.

 

[R413]

Make sure the seats have good gaskets and are tight to the top of the carb. If they leak there it will cause your problem.

Are the floats empty or do they have gas inside?

Are the floats parallel to the sides of the carb and nit running on the float bowls?

Did you rebuild both? Are there loose screws on both? Maybe recheck the other one too.

Check all the screws everywhere and make sure they are tight, the gaskets crush down. When I rebuild a carb I put all the pieces on and let it sit for a week with the top off then recheck all the screws again. Some are looser from gaskets crushing. Then I put it together and run it.

When working on carbs use good quality screwdrivers that fit the screws and are not worn. That’s how the slots get rounded off. How many times have we seen that on old carbs?

 

[ruffcut]

Could be a fine particle in the needle and seat not letting it seal properly? Believe me, I've had my share of things like that also with my Max Wedge, and also my old power wagon snow plow. It has an Edelbrock carb also. Happy hunting! ruffcut

 

[AR67GTX]

Floats are empty and good, hang right and move free. I checked the seats and they were tight. I rebuilt both carbs with kits from Mikes. - but I kept all the parts separate - no interchange. I checked the other carb screws and they were snug too, but not real tight. - I gave them about another 1/8 turn.

I really expected to find one bowl full and I was very careful removing the carb to my bench - no spillage. But as you can see the fuel was way down in the bowls. I’ll dab and soak the fuel out and see if there is any debris in there but fuel filters should stop it. I’ll check the seats and straight edge the cover too.

 

[threewood]

What is your fuel pressure? Anything over 6psi could push fuel past the needle seats. The Carter design is very simple. If you have too much fuel it is going to be 1) too much pressure, or 2) float/needle stick open.

 

[Fran Blacker]

R413 said it all. If you have a short piece of 5/16" flared tubing attach it to fuel inlet. Before you put the top on flip top over and blow through tube. If have a leak it's either the flare or needle and seat. Are the baffles hanging floats up?

 

[AR67GTX]

Turned out not to be such a big mystery as I feared. When I took out the seats the right side one had a moon slice piece of gasket in it that I guess when the fuel flowed, would stick an end in the orfice and kept the needle from seating. Couldn’t see it from the needle side. And most of the leaking did seem to be on the right side. The not-tight-enough cover screws probably didn’t help. If you enlarge this you can see the piece in there.

Now I have an exhaust manifold leak to address - must have missed tightening a bolt under there.

 

[R413]

Good job, keep looking and you will find it. The smallest of things can cause trouble.

 

[AR67GTX]

I guess what fooled me was that if debris was under the needle or the float was dragging, I expected the bowl to be filled up nearly to the top. But I guess that once the engine is killed it probably siphons out through the jets and fuel passages until it’s drawn down near normal. So much for “we won’t be fooled again”.

 

[R413]

Yes it leaks out into the engine. But the telltale sign is the other area filled up where the weights are on the secondary air flapped Plus when you take the top off the floats are now out of the liquid and it’s lower.

 

[ruffcut]

Turned out not to be such a big mystery as I feared. When I took out the seats the right side one had a moon slice piece of gasket in it that I guess when the fuel flowed, would stick an end in the orfice and kept the needle from seating. Couldn’t see it from the needle side. And most of the leaking did seem to be on the right side. The not-tight-enough cover screws probably didn’t help. If you enlarge this you can see the piece in there.

Just as I expected! Glad you found it! ruffcut

 

[Dragon Slayer]

What is your fuel pressure? Anything over 6psi could push fuel past the needle seats. The Carter design is very simple. If you have too much fuel it is going to be 1) too much pressure, or 2) float/needle stick open.

This may be true for Edelbrock and Holley, but not for Original Carter carbs. Chrysler called for a high fuel pressure spec. Primarily to prevent vapor lock and keep the fuel moving to the carburetor in a liquid state.

If the floats are correct version, and the seat is correct diameter carter run at the higher pressure and are calibrated for it. Lower fuel pressure lower fuel level unless you adjust float. Change to a larger seat and that usually is the problem you significantly raise the fuel level because the area the needle seats against is larger and more force applied to float. So float has to have more fuel rise to create the buoyance force to shut the needle against the higher force. Hence a lower fuel pressure would be needed, or you need to adjust the float to compensate and get the correct level for calibration.

Edelbrock used larger seat and smaller floats hence the requirement for lower fuel pressure.

These hemi carbs used a #38 seat (.1015dia). Usually you find #35/34 (.110 or .1110). That is a 20% increase in seat area.

Glad yours was a simple issue. Hope to hear how it is running soon

 

[AR67GTX]

Should have followed up that all is now well with the carbs. I installed new fuel filters with that KV marked hose just before this. I think that black curved sliver must have been shaved off the edge of the hose by the lip of the metal fuel filter as I pushed in in, even though I lubed it up first with some silicon grease. Considering everything that’s pretty much the only place it could come from. The carbs were throughly sprayed out and blown out during rebuilding

 

[Fran Blacker]

Bought a couple of Fram plastic filters that look like originals. One was USA made other Brazil. Will try to polish off Fram logo and pressurize them with 20 lbs of air an let sit and hope they don't blow. Bought two of the blue decals so if they don't pop. One those if I get around to it projects. Not mine. https://www.ebay.com/itm/154728218948 https://www.ebay.com/itm/154818208720

 

[R413]

To me it just is not worth the risk using those plastic filters, especially on the top of an expensive engine like these.

The factory used them, and unless you have a concourse show car then don’t do it. Junk like these plastic time bombs will never be soon on my car.

 

[Fran Blacker]

To me it just is not worth the risk using those plastic filters, especially on the top of an expensive engine like these.

The factory used them, and unless you have a concourse show car then don’t do it. Junk like these plastic time bombs will never be soon on my car.

Who ever buys my car might want to go with them if they restore it. They won't go on the car while I own it. I'd run a bead of crazy glue around the joint.

 

[AR67GTX]

Damn - after finally getting the exhaust system straightened out and the underside of the car put back together, it was time to start the engine and try to calibrate the tach to the new circuit board.

I had briefly started the car twice since believing I had the leaking front carb fixed and although I only ran it a few minutes each time due to exhaust manifold leaks, the carbs didn’t act up.

Not today, the damn #@??!!##/ thing. I primed the rear carb and it started up immediately and ran OK for about 10 seconds and then started loading up. I glanced around the edge of the hood and saw gas flowing from all four bowl vent holes in the top casting, above the bowl chambers. Immediately pulled the carb off and stripped the top off and gas levels normal but gas everywhere in the carb - where it shouldn’t be.

Pulled the needles and seats and both clean. Blew out the fuel passage into a clean paper towel - nothing. It was clear the left side leaked a lot more than the right side from fuel collected in the manifold recesses. But there is a passage in the upper casting, at the rear, connecting the bowls so the needle/float/? probably hung on the left side, flooded that bowl and ran around to the right bowl, filled it and it started running over just as I shut it off.

Set the needles in the seats placed inverted on a piece of dry wood and filled the cavity with gas to see if either would seep gas past the needle with just their weight seating them. They held the gas and didn’t seep but not sure that proves anything. Both floats are obviously dry. I don’t think it’s the fuel pump as the back carb has been fine, before rebuilding the carbs they were fine, and it’s run a couple of times for 5 or 10 minutes in recent weeks and didn’t mess up.

I guess I’m going to order a couple more needles and seats from Mikes Carburetors again. If it happens one more time I’m just going to bundle them up and send off to Woodruffs and let the damn thing sit for 4 months.

Anything else I might be missing?

 

[Demonic]

In the first post, second pic, it looks like a couple of little bits in the bottom bowl? I'd get a gauge on the fuel inlet and check the pressure, as others mentioned.

 

[AR67GTX]

I’m pretty sure the pump is OK, it’s an older pump and worked fine when I got the car last year without these issues. But when I get the carb back on it again I’ll hook a gage up to that fuel line and check it. I’m going to see if our local speed shop has a couple needle/seat units and go over the float mounting and freedom of movement intently and see what happens.