low compression

I am trying to start a 53 ford flathead that has not run for several years. It will not fire at all. I checked the compression and got a reading of 25 lbs. I added oil to the cylinders and got a reading of 50. I don't understand why the reading is this low. I pulled the heads and checked the cylinders for excessive wear and did not find anything obvious. I am confused. Does anyone have more things to look at?

 

Valves crusty and not closing all the way?

 

I lapped the valves

 

How much wear in the cylinders? Rings could be stuck in their grooves.

 

I had a 1938 Ford Truck with a no start condition. I checked and had spark and fuel.
In desperation I poured a little gear oil down the carb.
Got the the thing started.
I certainly wouldn't try this on a newer OHV with higher compression. Might hydrolock the motor.

 

Marvel's Mystery oil may help with stuck rings. As mentioned, take a good gauge and see if your cylinders are tapered or oval.

 

I checked the cylinder walls and there is no ridge at the top at all. No scratches on the walls either. I t seems odd that there is low compression and no visible reason.

 

Is your gauge known to be good? Did you check all cylinders?

Has it been bored?

 

I did not check the bore size, but I do not believe it has been bored. The gauge is the type with the rubber end that you hold in the spark plug hole.

 

Be sure when you go to start an engine treated with a Marvel Mystery Oil soak to loosn the rings that you do it outside or have several several box fans blowing from inside to outside the garage. When that baby fires it will lay down a smoke screen for 5-10 minutes or more and cover the nearby area in a thick aromatic bue fog.

 

That keeps the skeeters away! It says so on the back of the can...

 

See if you can a hold of a cylinder leak down tester. Was the throttle held open when cranking on the compression test? Is something blocking the intake?

 

If the cylinders are not tapered and the pistons tight in the bores and you ground the valves the only other explanation is stuck rings.

Here is what you might do. Pour MMM in the cylinders as suggested. Let it soak for a week. Put the heads back on. Oil the cylinders one more time and try starting it on the end of a tow rope. If it starts keep it running at a fast idle for 15 minutes to a half hour. Be sure the crankcase is full of oil and the rad full of water of course.

After 5 or 10 minutes it may settle down, run smooth and idle down to a normal idle. If it runs smooth with no knocks or bangs, good oil pressure then it will probably come back to life and gain its compression back. It may take a few hundred or a few thousand miles of driving to free up completely.

 

Those gauges suck.

What history do have on this thing ?
Valves that don't close = zero compression.
Valves that open or close early or late = low compression.
Rings kinda sticky in the piston grooves can give low compression.
Rings stuck hard in the ring groves usually gives no compression and a tight to turn engine.
Adding oil and seeing a rise in compression is pretty text book for a ring issue-
Sticky or worn.

 

Damn it Dane I had to explain to coworkers why I was sitting here laughing my ass off again

Jerdan, remember that that engine has been sitting for X# of years and there was a reason that it was setting and that may have been that it had low compression when it was parked.

I'd say that if everything else was right it still should start with around 50 or 60 lbs of compression especially if the compression is even all across.

I'd go along with squirting some Marvel Mystery oil down each cylinder, crank it over a few times to get it splashed around and worked in and screw the plugs in loosely and let it set for a few days and then pull the plugs and crank it to make sure you blow any excess liquid out and put the plugs in and see if it will fire up.