Shorting Plugs has no effect

[TinCup]

Recently put a new head on a car that had been setting for over 8 years due to a cracked head. I went through the valves and have installed known good plugs, distributor, carb, coil all the things that make this car go. I have set the timing so many times I have visions of the rotor at 4:00 in my head. Verified timing mark and TDC.

Car runs lousy. Stumbles as if it was missing but only number 4 plug can short to the block and cause it to stumble. I have good spark at all 4 plugs.

Throw this dog a bone I am tired of chewing on this.

[George Miller]

Do you have compression on all 4 cylinders. If so how much?
You say you went through the valves. Does that mean grinding them?

[TinCup]

Sorry forgot to mention 60-65 all cylinders. Gapped all valves.

[George Miller]

Originally Posted by TinCup

Sorry forgot to mention 60-65 all cylinders. Gapped all valves.

I would check for a vacuum leak at the intake. You also could have a sticking intake valve.

[BILL WILLIAMSON]

Kinda' weird, TinCup,
Compression tests indicate that valves are OK.
Are you using manifold gland rings? "Maybe" 1 is cocked or too thick to let the manifolds seat against the block well??
Spray a little Chem-Tool or Propane around the manifold gasket & see if it RUNS BETTER. "Maybe" a rag or paper wadding got left in intake manifold??? Or "maybe" the exhaust might be plugged???
Bill W.

[1955cj5]

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You might try a different (new) set of plugs, or swap the ones you have around and then see which cylinder stumbles...

[George Miller]

Originally Posted by George Miller

I would check for a vacuum leak at the intake. You also could have a sticking intake valve.

The reason I said it could be a sticking valve is because you had a leaking head and then it set for many years.

I have seen sticking intakes on many Model A's that had been sitting over the years. They could have compression when turning slow with the starter, but slow to close when running. If it is not the intake manifold leaking you might try mystery oil in the gas, or through the carb intake.

[5lugnuts]

Change the condenser!

[heneste]

Is it possible the number 4 spark plug is cracked anywhere? You would still get spark but it may be shorting out under load.

[Dollar Bill]

I had the same symptoms you describe. Resolution was vacuum leaking between intake and block due to a faulty gasket.

[johnbuckley]

Originally Posted by heneste

Is it possible the number 4 spark plug is cracked anywhere? You would still get spark but it may be shorting out under load.

Surely as I read #1 , it's cyl number 4 that's doing most of the work!? Or is something missing on this transatlantic transmission?
Is idling and powering under load equally bad, Tin Cup?

[johnbuckley]

Originally Posted by Dollar Bill

I had the same symptoms you describe. Resolution was vacuum leaking between intake and block due to a faulty gasket.

test for this by spraying Eezy Start at the gaskets there- careful it's explosive!

[MikeK]

The dizzy body may have an internal arc-over short. Try a different one.

[pooch]

Try running it with the brass plug strips off and about 1/4 inch away from dizzy cap, forcing the spark to jump to each strip, and then short out each plug.

[daveymc29]

I had a valve slow to close. Put Marvels Mystery oil in the cylinder and cranked it over with the key of, put a tad more in the spark hole, put the plug in, cranked again a few revs with the key off, let it sit over night and have driven faithfully for the last several months. I do put about 2 to 4 oz of MMO in the gas tank on each fill up if I remember to do it. Helps with the carb float valve sticking also. Our gas-o-crap is awfully dry, doesn't lube anything passing through.

[meteorgray]

Had the same issue with my 40 buick. Seemed like a fuel problem. I,m with 5lugnuts it was the condenser.

[TinCup]

Change plugs today with no improvement. Also reinstalled the original distributor with another diz body that I rebuilt and there is no change in the behavior. The lopping is more pronounced at low rev that higher rpm's. Added some MMO to the gas and oil today and ran it for a good 30 minutes. Going to let it set overnight and see if it has any effect on the valves.

I replaced the exhaust and intake gaskets but I am going to pull it tomorrow and replace them along with another intake and exhaust and see if that is the culprit.

I have a little water coming out the *8 stud but it's just a drop or two. Other than that the head was torqued to 55.

If I hook up the vacuum gauge what should I be looking for.

[Tom Wesenberg]

Look for a bouncing needle if you have a sticking valve.

[1955cj5]

I agree with John from across the pond........If the car stumbles badly when shorting #4, I would say #4 is doing it's job correctly, but when taken out of the picture the stumble is more noticeable.

If you short the stumbling cylinder the stumble should go away... the engine will run poorly, but smoothly...

[jm29henry]

Check the la,laminated timing gear ?

[TinCup]

Replaced the intake and exhaust manifolds with a spare and the car now runs. One of the middle exhaust had a cracked ear and was blowing directly on the intake port. Vacuum gauge showed the manifold leak. All is back together and even took it down the street for a drive but it is a tired motor. More noise from the valve chamber than I would like and according to the vacuum gauge either sticking or worn valves. Placed my gauge on a newer Ron Kelly motor this morning for comparison and it showed what it should be not what I have. Between the shorted coil and the manifolds this has been anything but usual. Thanks for all the input. I am now a firm believer in the use of the vacuum gauge.

[Mike V. Florida]

Originally Posted by TinCup

I am now a firm believer in the use of the vacuum gauge.

for those that have little knowledge of the gauge;

http://www.secondchancegarage.com/public/186.cfm

[BILL WILLIAMSON]

Originally Posted by Mike V. Florida

for those that have little knowledge of the gauge;

http://www.secondchancegarage.com/public/186.cfm

And if you SLOWLY rev it up to about 2,000 RPM & the gauge SLOWLY goes to "0"--the exhaust is PLUGGED UP.
Bill W.