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Flooding Issues Across Multiple Carbs

2682 Views 27 Replies 8 Participants Last post by  valiant67
I'm working on a '72 Plymouth Fury III with a 360 and a two-barrel carb (it's a Holley 2210, I believe).

The original carb was shot (previous owner already rebuilt it and it still had some major issues), but it did run.

Bought a rebuilt carb from AutoZone and put it on the car. Car ran great, but after a few days while working on some other things I noticed the fuel inlet was leaking gas.

Checked it out and the carb itself was stripped where the fitting screws in. I wasn't terribly pleased but there was threading past the striped area, so I replaced the fitting with one that had more threads and stopped the leak. During leak testing I only ran the car for a short period.

Next day I hopped in the car and took off and got about half a mile from my house when the engine bogged down and died. Popped the hood and the carb was flooding now. Aired things out and drove back home. Sick of the issues with the new carb, I took it off to return it. Put the old carb back on and it is now flooding as well.

Only thing I can think of is the pump is putting out too much pressure. But I find it odd that the pump would be fine and then fail in this way. I've heard of pumps failing to pump enough fuel, but suddenly pumping too much?

I'm going to have the parts store order me another carb and I'm going to order a pressure gauge to review the fuel pump, but these things will take a couple days to get here, so I thought I'd get some opinions from the experts on what other issues I may want to chase down while I wait for my supplies to arrive.
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With all due respect, Bob, with every other carb I've ever messed with in over 35 years of cussing at and hammering on older Mopars,(2 and 4bbl models), "In" is rich, "Out" is lean. You're turning it out (counter-clockwise) to allow more air (not fuel, hence the reason it's actually the Idle Air Circuit we're talking about) in. The idea is to keep the curb idle speed screw barely turned in, so the carb is drawing air and fuel only through the idle circuit. By turning the idle mixture screws in, you reduce the amount of idle air, requiring more idle speed screw adjustment, opening the primary throttle plates, negating the idle circuit (and ported vacuum draw) which then requires more fuel. The FSM would obviously be the place to confirm the direction, if anyone has that.

Thinking back, I actually had this same set-up on my very first car, a '77 Fury with the E57 360 2bbl, but I can't recall anymore which way the mixture screws went. It's possible that particular carb is arsebackwards, where "in" would be lean, but I wouldn't bet a penny on that.

One last note to the OP - check your base timing, and also double-check your crank dampner. Agreed on keeping it stock. Yes, even an NOS ebay carb would need a gasket kit with Viton seals for today's fuel. There is a boneyard near me (western WI) that is a no-crush yard, but I think if you replaced the choke pull-off (vacuum kick), you should be in pretty good shape. The 360 is a bit more tolerant of carb issues than the 318. The 318 will run beautifully with just the right mixture and timing. The 360 seems to be less fussy. Just my experience.
Of the hundred carbs I have done, out was richer and in was leaner. To get a turn difference there has to be something different between the two idle circuits. Damaged needle valve or seat or blocked idle venting port. All later carbs are designed to drop the idle circuit out as venturi speed goes up. They did it with air bleeds which by design are very small.
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I went ahead and made an adjustment to the vacuum brake (think I'm using the right term here) so it holds the choke open what looks a little over double the original spec after the vehicle is started. Did a cold start and it ran fine; not perfect but not too bad. Fast idle was a little too high for me, so I'm hoping I can drop that down and still have the engine run alright, but I have to wait for the engine to cool back down again. Is having to set the choke so far off spec a bad sign? Does this mean this carb runs super rich and will get atrocious gas mileage?

I also changed the idle mixture screws again once the engine was warmed up so they were both at about 1 turn each (like they were before). Didn't use a vacuum gage this time, but by ear that actually sounded a tiny bit better. I already drove the car at that setting for a few days without issue, so I'm sure it's fine.

Without the car bogging down while warming up, I'm not seeing gas drip anywhere anymore. Still seeing some small moisture accumulation in the trouble areas from before, though. I assumed this was gas before, but is it possible it's just condensation from the air that sticks as the car is running? If it's not actually a gas leak, I'm considering keeping this carb instead of returning it since I've about got the cold start issue worked out. I'd definitely rather not spend $450+ dollars and go new aftermarket if I don't have to.

One last note to the OP - check your base timing, and also double-check your crank dampner.
What is a crank dampener, and how would I go about checking it?
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This car has points or the electronic ignition? Set dwell first if points.
Clean & mark the timing marks with white paint for easy viewing with a timing light.
The distributor advance hose should be disconnected & plugged while setting base timing.
It should be ported, not intake manifold vacuum.

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Thanks. I assumed the car had points because of the age, but maybe not. I'll have to take a look and see. Any quick way to tell other than pulling the distributor cap and looking inside for points?

A couple other small questions that still feel relevant to this thread:
  • As a 1972 model year, this car should not need leaded fuel, correct? My understanding is that if a car needs leaded fuel and you don't put an additive in (since you can't buy leaded fuel anymore), it can cause valve damage.
  • I have an unopened bottle of Marvel Mystery Oil (original formula). It's enough to treat two gas tanks. Would there be any benefit to running this in this car? (As a reminder: the car sat for twelve years, was driven a little bit three years ago with the junk carb, and then hasn't done much other than occasionally get moved around my property since then.)
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For the 1973 model year, all Chrysler products had electronic ignition. Some had switched over in 1972, mostly the big blocks, I think. If it has electronic ignition, there will be a module mounted on the fenderwell.

Leaded fuel was specified until 1975, when nearly all cars were equipped with catalytic converters. It's possible that some engines had hardened seats and valves a few years prior, to prepare for the change.
MMO won't really do anything for your fuel system. Techron might.
Couldn't find a module on either fender, so I'm thinking it must use points.
EDIT: My car did have electronic ignition. Module was mounted on the firewall at about the same height as the voltage regulator but closer to the fender. It's pretty obviously visible; I just had tunnel vision.

Any way to know if the valve seats are hardened on my car? I vaguely recall hearing in the past that Chrysler was ahead of the curve in the early '70s on meeting pending emission regulations, but I have no idea if that's actually true.
EDIT: Didn't want to bump this thread, but did want to leave this information here for posterity. I got my hands on an original 1972 Plymouth Fury operator's manual, and it says the following:
The 1972 passenger car six cylinder engines will operate satisfactorily on either leader or unleaded regular grade fuels.

Uninterrupted use of unleaded fuels without anti-wear additives is not recommended for our V-8 engines if vehicle usage is predominantly under conditions of expressway speeds, or if the operation involves trailer towing. For these conditions, at least one in every four tankfuls should be leaded fuel. If this precaution is not taken, valve seat wear may result causing excessive emissions and possible engine failure.
The manual also says 91 octane fuel is required in the paragraph before these.
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We started using low-lead gasolines in the early '70's. The exhaust valves & seats were hardened to a degree. It isn't a high-performance engine requiring premium gasoline. It is probably fine with unleaded.
The car may never be a daily driver accruing lots of miles, so I would leave it as is.
On a street driven car, especially one that’s not an HD motor, it probably will be fine even without hardened seats.
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