Poor Compression 221 2 cyl's

T

tucker6077

Member
Would putting in a colder or hotter plug help fire a lower compression cyc? 1933 ford 40, aluminum heads. Also any known reputable mechanics to work on this vehicle in NJ,PA,OH,or Delaware
 
No, low compression is unaffected by plug temperature. If you are fouling plugs due to a worn bore and a lot of oil getting into the cylinder sometime you can limp things a little longer with a hotter plug, but it isn't recommended.
Why the low compression: valves, rings, gasket, other?
 
The engine was supposed to be rebuilt 80 miles ago. When the car is run the plug shows no sign of being fired but is does have adequate spark. Cyc comp is 60. Plug when pulled is wet with fuel. Could this correct with a longer break in period? Thank you for any help !
 
What plugs are you using? don't use resistor plugs. Where did you check for spark? Pull the plug and grounded it or pulled plug wire and grounded it? What kind of plug wires are you using? use wire core not resistor carbon core. Have you changed plug with a cylinder that is firing? Does the engine have a good ground.
Is this an original 33 V8 engine with original distributor and coil?
 
If they cylinder is wet and you have compression, then you most likely have an electrical issue as the cylinder is not firing. I'd have the distributor, wires and plugs checked out.
 
If what B&S checks out OK, I would suspect bad valve adjustment. Good luck. Were you checking compression with WOT (wide open throttle)?
New rebuild, were heads retorqued at least 3 times?
 
60 psi cylinder pressure is low in my opinion. Was that checked on a cold or warm engine? In the last year I have put 1,000 miles on a 1937, 221ci engine that has between 65-70 psi warm. It uses oil and is low on power. I will be replacing that engine with a fresh one this fall.
 
A leakdown test done by somebody with the right equipment and knowledge would be a great idea. But, if he is truly seeing 60 lbs of compression, the cylinder should fire. Maybe it doesn't fun perfectly, but it should fire and the plug should not be wetted down. Another suggestion is to put NGK plugs in it.

If you happen to be using Champion plugs, I've seen many cases where once they're fouled, they will not fire again. Folks have argued with me about this, and I've had to show them (multiple times) at the racetrack!
 
Bored&Stroked said:
If you happen to be using Champion plugs, I've seen many cases where once they're fouled, they will not fire again.
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I have read that the porcelain was not sealed properly and once fouled would absorb carbon, oil, and short out internally. No amount of cleaning would fix the shorted porcelain with internal carbon tracking. I think Champion was not the only plug with that problem, but they were the easiest fouled.


Try swapping plugs from running cylinders to the not firing cylinders. If the engine has only 80 miles it is possible the rings have not seated because the cylinders are not firing and are gas washed. If swapping plugs gets those two cylinders to fire then a new set of plugs is needed.
 
Seth, my 85hp 37 has about 70lbs compression across the board and runs like a raped ape, no loss of oil.
 
tucker6077 said:
Well That last post has given me hope ! Anyone know of a flathead mechanic in NJ ? :)
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Even with low cylinder PSI, the engine can run. I could probably drive another 1,000 miles on my tired engine but I'm looking for better power. I'm also getting tired of the blow by smoke.
 
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