Need advice to fix rough running engine.

[Terry,OH]

Usually Max is very close with Carb. jetting but from the sound of things your running rich with carbon on the floor and the plugs, two plugs with black deposits! Are the inner distributor caps new?. Look into why two plugs are fowling, wires, rotor to cap gap, wires in the incorrect position, bad plugs. Take the fuel pressure down to 2#. What size jets are in the 97's? Mains and PV.

[Graeme / New Zealand]

Originally Posted by Ken/Alabama

Did you bypass the resistor under the dash when you installed the round coil?

This is very important if you install a round coil. When I had a round coil I did not do this and the car ran like a "hairy goat". When it quit I got a rebuilt original coil from Skip and the car has never run better and starts straight up without all that cranking. I came to realise I was effectively running through 2 resistors because of the inbuilt one in the round coil.

GB

[FlatheadTed]

It does still sound like fuel or electrical but its worth a look at the valves ,The vacuum gage as suggested would help pin point a vacuum leak etc but as you say you have eliminated that .I would even consider changing back to stock parts one carb until you get it sorted ,Bad ING switch or connections can give a drop in voltage a jump wire is a way of by passing that and the resister ,It sounds like you have already done that .If you run the revs up and a blue spark turns to yellow that s worth a try also .Ted

[39topless]

Originally Posted by Terry,OH

Usually Max is very close with Carb. jetting but from the sound of things your running rich with carbon on the floor and the plugs, two plugs with black deposits! Are the inner distributor caps new?. Look into why two plugs are fowling, wires, rotor to cap gap, wires in the incorrect position, bad plugs. Take the fuel pressure down to 2#. What size jets are in the 97's? Mains and PV.

Main jets= .043 PV= #69 I am at 5000' altitude (Denver)

[39topless]

Can't run the vacuum tests, jump wire, check for bad plug wires etc until I replace the bad water pump which will arrive Tuesday. Already tried running with one carb. Tried each one with no positive results. Ignition does not run through an external resistor under the dash. My hunch is a bad valve or a possible vacuum leak in side the intake (as suggested). Once the water pump is replaced and I can start engine, I will do all the tests and jump wire as suggested here first. I also just bought a rebuilt distributor with a stock coil. I will try the stock coil along with a new stock resistor and condenser that will arrive with the water pump. If no luck, next step will be to remove intake to inspect valve action.
Thank you all again and I will provide an update.
Phil

[Ross F-1]

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Originally Posted by scooder

You say no vacuum leaks, it's possible that there's a vacuum leak from manifold to the valve chamber, the inside of the port. I've had this once.
Can't find it the usual way of spraying stuff around the manifold, only see it when the intake is removed, mine had a section of gasket gone from the inside of the port. Mine had the all the plugs clean bar one that was carboned up, it was the one from the bad gasket part. Theyll pull air from the valve chamber into the cylinder.
Yours had six clean plugs, two dirty ones. Sounds similar, definitely worth a look if all the other stuff is good.
Martin.

I've seen one that someone prying on the valve guides broke a chunk off the side of an intake port at the gasket surface. They had JB Welded it, which eventually failed for the new owner. Like you said, absolutely no way to diagnose.

[Terry,OH]

The jet sizes are a good starting point. If the engine lacks power going, after a stop increase the mains one size if it soots up the plugs decrease. Find your other problem before changing the jet sizes. A rich jet size will soot all the plugs not just two.

[BUBBAS IGNITION]

Originally Posted by 39topless

i need some advice on where to look now for the root cause of my engine running like a slug up hill in a sand storm. My engine is a 39' 221 v8 that's stock except for finned heads and 2x2 carbs with a "super" type intake. Fuel is supplied by a holley electric pump and regulator set at 2.5 psi. Ignition is a stock helmet type distributor with "tube type" coil and adapter. Symptoms: It starts ok and idles ok but with a slight hitch in the rhythm. There are spotty black deposits on garage floor rich below exhaust pipe. On acceleration, it cuts out, occasional back fire thru exhaust, and slugs down the road as if running on 6-7 cylinders, choke or no choke. fuel ? it is one gutless sob.
My unsuccessful remedies to this engine illness include the purchase and installation of: Rebuilt carbs (97s) by uncle max, rebuilt distributor by bubba (recently rechecked by bubba), two new coils and a new coil wire, three new condensers (napa rr174), new set of spark plugs, replaced inline fuel filter and flushed gas line.
Tests and procedures include: Check for vacuum leaks (found none), checked spark plug wires and coil wire for spark on cranking (adequate blue color), checked accelerator pumps in carbs for gas flow (ok), compression check (lowest=80 all others 90-110#) with all plugs out and carbs open. Removal of plugs revealed two with lots of carbon deposits and all others clean.
Questions: Will a bad valve always reveal itself in a compression check? What should i check, and or, try next? Thank you.
Phil

fuel fuel condensor ? Engine mechanical???