|
Don't mean to throw a monkey wrench in here, but are you talking "dry compression" or "wet compression"? The "wet compression" is done with about a tablespoon of oil squirted into the cylinder, and should be considerably higher. The 98PSI number sounds a little low to me, not familiar with what the book says, but 125PSI sounds about right, probably dry. As a comparison, I recently replaced a head gasket on an 8N (which runs comsiderably lower compression ratio, i think 5.5 on a flathead) for my brother in law. A compression check afterwards yielded 110 to 117 PSI on all cylinders dry, and 135 to 138 PSI on all cylinders wet. I found these to be excellent numbers, the cylinder bores on this 50 year old engine with about 2000 hrs and no rebuilds looked fantastic! The 8N book calls for a minimum 90PSI and all cylinders within 10%. If you are experiencing low compression on one or more cylinders, and the "wet" number is higher, then the likely cause of the low compression is a bad valve. If the "wet" number isn't much higher, then the likely cause of the low compression is badly worn piston rings. Also, make sure you are doing a correct compression test. Engine should be started and run to bring up to operating temperature. Engine is then shut off (preferably by shutting off fuel supply, thus running it dry), ALL spark plugs removed, choke off, throttle wide open, and compression tester installed on only one cylinder at a time. Make sure to turn engine over a minimum of 5 compression strokes. Hope some of this helps; or if you'd rather, you can tell me to go jump in a creek. Good Day!
|
