Technical Triple Deuce Missing & Hesitating

Just built my 31 Ford and put 230 miles on it last weekend with no missing / hesitation issues. Got in Tuesday morning to go to work and had lots of missing / hesitation at highway speed. Last night took the plugs out and noticed lots of black carbon on them. So I assume that the engine is running too rich. So I adjusted the primary / middle carb screws with a vacuum gauge. I set the lean/rich screws to the highest vacuum reading. I hooked the vacuum gauge up to the primary carb vacuum port. I put new plugs in gapped to .045 and went out and ran it. Ran good. I came back and took the plugs out to see if they had carbon build up.... They did. I cleaned the carbon off the old plugs and gapped them to .060. Put them and took a ride. Ran a bunch better.... Thought I fixed my problem. Got in this morning and got back on the interstate, same thing. Spit, sputter and hesitation at cruise speed fixed throttle. Acceleration, it seams to get better. When I downshift and open wide throttle, all 3 carbs full open, it shits and gets with a little hesitation. That seams to clear up the missing at cruising speed for a minute...then back to spitting. Any help would be great!!!!
-Engine Specs-
-1978 SBC 350, 010 block, original not rebuilt
-New oil pump and timing chain
-350 hydromatic trans
-Factory torque conv
-Rebuilt Rodchester 2 Jet carbs (center is primary front and back are dumpers)
-New Offenhauser trip deuce intake
- New Pertronix Flame Thrower III mechanical advanced distributor (electronic pickup)
-New cap and rotor
-Baffled headers
-8mm Mallory spiral core suppression wires - new
-New 45k volt Pertronix flame thrower coil
-Timing set at 8-10 degrees advanced
-PCV valve ran off of primary carb vacuum
-20w-50 oil
-oil pressure at idle is 35 psi
-oil pressure at highway speed is 72 psi
-Engine never runs past 200 degrees
-New OEM Dampner / Harmonic Balancer
-AC Delco R44T plugs gapped at .06
-New mechanical fuel pump
-No fuel pressure regulator
-I have never measured the fuel pressure
-Engine starts and idles fine. Sometimes it spits under light to moderate acceleration.
-Trans vacuum is hooked up to intake manifold.
-Mechanical non clutch factory fan
-Fuel filter is between tank and mechanical pump.
-Hard fuel line from mechanical pump to carbs. Rubber hose from tank to mechanical pump

 

Sounds like you need a fuel pressure gauge. HRP

 

I just installed a fuel pressure gauge. Reason at 6.5 psi

 

Way to much fuel pressure. HRP

 

I agree. I run my 2g's at 3 psi. I tried to run them higher at first and it wanted to flood out. It's been perfect since I turned it down.


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I set my Mr Gasket fuel pressure regulator at 3.5-4.0 on my Offy/3 deuce 2G 350 Chevy.
No issues except for the 10% ethanol /gas evaporates if I don't drive it for a few days. I add that Lucas product for ethanol too.

 

What mods did you do to the center carb? This car probably won't cruise smoothly at light throttle with a stock setup on that carb.

 

I bought the set up from an old timer that builds them. Got it at a swap meet. So I really don't know what mods have been done. I just added a fuel pressure regulator. Seams to have fixed the problem. The test will come tomorrow morning on the interstate!

 

So it was better for longer but back to hesitating.... Fuel psi is almost 3 at idle. It almost feels like it is starving for fuel. But when I put my foot in it, it accelerates good w/ a couple little spits an misses. It clears up the prob when I am back at fixed throttle but just for minute. The missing and hesitation starts real slow and you can hear it in the headers just before you start to feel it. Crazy question...Under fixed throttle @ 60 mph, could the primary bowl slowly be draining to a level that would starve the engine.... Then under full acceleration, w/ the higher RPM's the bowl fills to a good level again?

 

Does the center carb have holes drilled in the butterflies?

 

For an engine miss, I'd be looking at the ignition system.

 

I bet your sec carb throttle blades have a gap around them pulling fuel in making her FAT!

 

No holes in butterflies but 1 hole in the bore above each butterfly

 

Based the engine specs above, what do you recommend?

 

What is the best way to see if the sec carb blades have a gap?

 

With the engine idling, cover both outboard carb horns tight, and the RPM shouldn't change IF the outboard carbs are closing well.

The hole above the butterflies is located for a stock single carb engine. It's in the wrong place & the wrong size for your setup, unless it's been modded (which is why I asked about mods.)

Drilling the primary carb butterflies will compensate for that, but the outer carbs must be closing well or it'll never idle down.

 

choose your info carefully ---some of it is pure BS

 

Covered outside carbs...Absolutely no change in RPM. Should I try hotter plugs? Currently using AC R44T. Should I try AC R45T or R45TS to get the spark more to the center of the cylinder?

 

Do you recommend anything?

 

Now, see, this is incendiary, yet it doesn't help anyone at all because you post no examples, no info, & no proof.

Just what appears to be BS?

If you have the time to shout BS, then maybe you could have the courtesy to be specific.

You might raise an argument (and there's nothing wrong with a good argument) but at least you won't be trolling.

 

I can't help at all with plugs for that engine, except to say you can clean the plugs then run the engine in the ragged range, then kill it without coasting, pull the plugs & take a reading.

The thing is that if the carb is off, you'll likely end up changing them again when it gets corrected.

 

Agree! What about hotter plugs?

 

If it didn't change the hick-ups by reducing fuel pressure, I doubt this is the case. If the float level was sinking at cruise, it should get worse when you reduce fuel pressure.

 

If you're keen to try hotter plugs, I'd first try to increase the plug gap another 0.010" & see if the running changes. If it runs just the same with a wider gap, the plugs and ignition are probably OK.

I think you need more idle air, but the thing is, is your primary throttle 100% closed at idle? I mean are you only idling off air the new holes supply? If so you shouldn't drill bigger IMO, but if not you might drill them a little more, like another 1/64" & see what changes.

Have you tried WD-40 or propane enrichment as a vacuum leak detector? A small vacuum leak could be causing this IMO.

 

I don't have a problem with idle... Problem is missing and sputtering sometimes under acceleration and fixed throttle on interstate. Opening all carbs wide open seam to clear the problem up temporarily.

 

Don't know he ws-40 or propane trick....?

 

Hey, I just re-read your first post, and I missed the fact that you already re-gapped the plugs & that this all just started suddenly. I thought it started right with the new Offy intake.

So if it changed overnight, I'd be looking hard for a vacuum leak or dirt in the carbs.

 

You spray WD-40 or an unlit propane torch around all the gaskets & hose fittings while the engine is running. If it gets sucked into a leak, the RPMs will change. RPM goes up if it's already lean, and down if it's already rich.

 

Everything I see you describing is a carb running too rich. The idle screws won't fix this part throttle issue.

There's a good chance something is wrong inside the carbs. Dirt, defective parts, seals, leaky plugs- Maybe too big of a jet? They are simple to rebuild.

Having said that remember that most carburetor problems are electrical in nature.

 

(Vick, LOL...only on VWs are they electrical...)

I'm not a specialist on your particular carb, Fordrat, but on the ride home I figured out three things.

First, if this carb has an economizer valve, it could be leaky, sticky, losing vacuum. A loose carb cover can make it lose vacuum on my carbs. The engine will sputter from a rich mix, because the economizer thinks the engine isn't making good vacuum yet.

(People usually think a vacuum leak means the carb goes lean. Well it makes it idle lean, and just off-idle will be ragged, but a leak at the economizer signal passage makes the carb go rich at light cruise.)

Second, IF the engine was really running perfect the night before this all started, the holes probably shouldn't have been drilled yet.

Third, I think this is perhaps what was being hinted about above. I think our drive-by poster understood that your car had a sudden issue. Fine last night, screwey this AM.

You don't cure a sudden issue by drilling holes in stuff unless it's an emergency.

You can however consider the drilling a diagnostic procedure if you like, because it did improve running, and that helps rule out ignition issues.

But IF you put on this new intake gear and then had your shakedown run and it went fine, maybe the shakedown shook a speck of dirt into a passage, port, or jet.

OH, I didn't mention that the propane is nice because it doesn't oil up the engine like WD-40, but if there's an ignition fault (you pulled all the wires and distributor to get the intake off?) it can ignite readily so beware.