Flathead coupe issues

Years ago I had a similar problem with my stock 59A, where at idle the engine would run smooth but under acceleration it would pop and buck. Turns out that the spark cable that ran from the coil to the distributor was burned out for about 1/2" up inside the insulation on the end where it entered the coil. I clipped the bad part from cable, soldered the wire to the end clip, reconnected it and the problem went away.
 
OK guys here's the latest, I refitted the original manifold with a new gasket and fitted a new not rebuilt carb , hooked it all up and ..........its running rougher than ever refuses to tick over below 550 rpm bangs and pops through the exhaust as soon as you touch the throttle and souñds very rough idling. I adjusted the timing on the distributor which did alter the running but only made it worse ! I changed the spark plugs, no difference at all. So to recap the car was driving OK but idled rough due to a leaking carb throttle plate spindle. Changed to twin Stromberg carburetors idle was OK but slightly stumbled now and again but backfired under acceleration and bogged down.the engine is running a pertronix ignition unit. I am now at my wits end and completely out of ideas
 
I have observed coils cause the difficulty that you are experiencing. Check for a white bluish spark at the plugs. Remove a spark plug wire and hold it about 1/2 inch from ground and see what you get. Are you using copper core or carbon resistor wires? Make sure all spark plug wire connections are good. On copper core spark plug wires I strip about 1/2 inch of insulation off and insert the wire thru the u clip, fold the wire over and insert into the socket. I have used that on a bucking 327 and it remedied the problem. You should also clean the contacts in the ignition switch and the connections to the ignition switch, ballast resistor, distributor primary lead, and coil using sand paper or file on the eye terminals and nuts.

Packard 440 copper core secondary wire for the high tension leads is excellent for a points and condenser system, but I have read that it causes problems with a petronix that you have.

For the vacuum adjustment, back the screw out until you feel resistance by using your fingers and lock it down.

You should have a negative polarity on the secondary of the coil - there is the pencil method or you can use a DC voltmeter - ground the plus lead and use the negative lead briefly on a spark plug terminal , whether 6 v or 12'v.

And your coil may have gone bad!!! But these are things that really help to making an engine run strong. Best wishes.
 
I have observed coils cause the difficulty that you are experiencing. Check for a white bluish spark at the plugs. Remove a spark plug wire and hold it about 1/2 inch from ground and see what you get. Are you using copper core or carbon resistor wires? Make sure all spark plug wire connections are good. On copper core spark plug wires I strip about 1/2 inch of insulation off and insert the wire thru the u clip, fold the wire over and insert into the socket. I have used that on a bucking 327 and it remedied the problem. You should also clean the contacts in the ignition switch and the connections to the ignition switch, ballast resistor, distributor primary lead, and coil using sand paper or file on the eye terminals and nuts.

Packard 440 copper core secondary wire for the high tension leads is excellent for a points and condenser system, but I have read that it causes problems with a petronix that you have.

For the vacuum adjustment, back the screw out until you feel resistance by using your fingers and lock it down.

You should have a negative polarity on the secondary of the coil - there is the pencil method or you can use a DC voltmeter - ground the plus lead and use the negative lead briefly on a spark plug terminal , whether 6 v or 12'v.

And your coil may have gone bad!!! But these are things that really help to making an engine run strong. Best wishes.
 
Sounds like ignition problem to me. Until the big issues get resolved, center the timing adjustment, and be sure the vacuum brake is down far enough to put some drag on the advance plate, just to be sure it is stabilized. I assume you found a way to hook up that vacuum line on your 2 x 2 manifold. You will need it.

I run Pertronix in my 59A/B with no problems, but there are two things to be cautious of. First, do not run solid core ignition wires; it needs the coil wound type center wire. Second, use the Pertronix Flamethrower coil with it; the 40,000 volt version, not the super hot 50,000 volt coil. The distributor cap may not handle the higher voltage. The Pertronix coil has the right resistance built in, so bypass the ballast resistor in the car.
 
Hi guys I've dug a little deeper with the coupe ignition and I concur I think ( hope) it is an ignition problem. I've come to this conclusion partly from the replies from you guys but also because the car is running a pertronix ignition unit and
1) the spark plug leads are solid copper
2) the coil is the wrong ohm value
3) the distributor cap is burnt and cracked
I've replaced the coil with the correct value unit, replaced the distributor cap and rotor arm, and I have a set of wire wound spark plug leads.
As soon as the leads turn up and I fit them I'll report back with the results
Cheers guys
Charlie
 
OK guys distributor cap changed, rotor arm changed, coil changed, air filters changed, ht leads changed. Distributor cleaned and overhauled, timing checked, confirmed no vacuum leaks. Car started immediately and still runs badly with an uneven idle, and backfiring through exhaust when revved, I'm all out of ideas now .
 
There are still a number of things that could be wrong. You need to confirm that you have a good spark at one of the spark plugs. You might try pulling high tension leads one at a time and see if you get the normal sluggish running on seven reaction with each one. If no reaction on one, you may have to check high tension wiring again or start looking for a leaky exhaust valve for one reason or another. The pump up compression readings can sometimes be deceptive. I use a differential compression tester but they are a bit more work and expense than the simple pressure gauge is. They won't deceive you though and you can tell where the leakage is with them.

The fuel pressure may be too high causing fuel to leak past the carburetor float valve. You can usually see raw fuel dribling around the air horns during idle if fuel flow isn't slowed up a bit there. You should get a noticable change of idle when turning the idle mixture screws if all else is functioning properly. If you have to close them off then there would be a leak in there somewhere.
 
Many thanks for the reply, I have checked all leads for a good strong spark and all look good, I've put a pressure gauge on the pump ) and I have a regulator in the fuel system) and its delivering a steady 2 1/2 psi so all good there. Altering the mixture screws does alter the running of the engine and I should have mentioned I also have tried a new standard single carb on the original manifold with exactly the same results, so I'm fairly confident its not fuel/ carb
 
Have you checked that the plug leads are connected to their correct spark plugs as in correct firing order. One crossed lead can cause problems like you have which means two cylinders are out of spark timing. Regards, Kevin.
 
Hi Kevin yes checked and rechecked mate, rapidly getting to the decision I have vale trouble I know they all open and close as I turned the engine over with the manifold off and could see them all open / close but guessing a burnt valve
 
If you can or have access to a vaccum gauge this will soon tell you if valves are ok or any faults like burnt valves.
A good steady vaccum at idle in the region of 17 to 20 is good but dependant upon what cam is fitted.
This is a good area to start as no dismantling required.
Phil Nz
 
Hi Phil
I've hooked up a vacuum gauge and I have a vacuum of 18" but the needle is not steady it fluctuates between about 14"- 19"
 
Sounds like you may have to check your valves. Even a small amount of leakage past will push unburned F/A mix into the exhaust system.
 
OK, I am late to this party. Did you time the engine with a light and verify that the timing mark is correct? You need to do that. Then put the timing light back on and just watch the flashes and see that they are nice and even with none missing. Your stock distributor will not work good with your dual carbs. Your vacuum controls are the problem with 2 carbs. Good luck, I hope you get it running great, Gary
 
I think he's running the crab type distributor. Not a lot you can do to change the timing there. Vacuum brake should work fine.

A sticky valve can sometimes work fast enough to get a compression check but can't close fast enough at high speed. That's where I'd look anyway.
 
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Cheers guys yes crab type distributor so timing is pretty much a preset, I've verified the vacuum brake is working , so I'm guessing valves are the issue . many thanks for your help guys
 
I don't know if you can get Marvel Mystery Oil in your neck of the woods but it works well on softening hard carbon build up.
 
If you are running the solid core wires with the Pertronix, it will more than likely not run right or, not run at all. I had the same experience with my car when I installed the Pertonix. Mine would run poorly for awhile and then, quit altogether. I changed the wires out (PITA) for radio suppression wires and has run fine ever since. I timed the engine, once it was running smoothly, by continuing to advance the spark until I got the highest vacuum reading I could get then, backed it off about an inch of vacuum. The good folks recommending a timing light may not understand what we're dealing with here. If, as you mentioned, it was running fine before swapping the Carbs, I wouldn't suspect valves to be the problem. The solid core wires with the Pertronix is problematic. Good luck and, let us know what you find.
 
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