The compression readings are fine on both motors. I am sure if you add oil to a brand new seated ring motor the numbers are still going to go up. If you are checking ring seal only,they have too. By adding the oil you are making a better seal and slightly decreasing cylinder area. Adding oil to a low cylinder, I mean like 40 points lower is used to help determine rings vs. valve leakage. A cylinder leak down test is much more reliable. The numbers gathered from both have to be considered in making a diagnosis.
Bad rings??
- Thread starter bobpogoman
- Start date
AND.....you can have 150psi readings, and still be blowing blue smoke out the tail pipe !!
How can that be(you're asking quietly inside your brain)??
Because the 'oil rings' can be bad (stuck or worn out).
It allows a larger film of oil to remain on the cylinder walls, and can actually make the compression ##s stay up some.
When performing (not doing) a compression test, just hold the throttle nearly wide open by wedging a tool or piece of wood at the linkage.
Perform on each cylinder 3x, writing down the 2 #s.
1st # is the 1st jump of the needle. This tells the condition of the valves. S/B about 90-100psi. If this 1st jump is below 70psi, you have a burnt valve starting.
60psi and lower, and you better do a valve job very soon.
I've seen many, many readings of 50-60psi (burnt valve) 1st jump, then work on up to 100psi final reading.
9x outa 10, its burnt valves that lowers your readings way down below 100psi.
Usually its only one exhaust valve that burns before you can't seem to get that 'miss' at idle to go away.
150psi on any motor is a good reading. It says the rings and valve are in good working order. :icon_bigg
How can that be(you're asking quietly inside your brain)??
Because the 'oil rings' can be bad (stuck or worn out).
It allows a larger film of oil to remain on the cylinder walls, and can actually make the compression ##s stay up some.
When performing (not doing) a compression test, just hold the throttle nearly wide open by wedging a tool or piece of wood at the linkage.
Perform on each cylinder 3x, writing down the 2 #s.
1st # is the 1st jump of the needle. This tells the condition of the valves. S/B about 90-100psi. If this 1st jump is below 70psi, you have a burnt valve starting.
60psi and lower, and you better do a valve job very soon.
I've seen many, many readings of 50-60psi (burnt valve) 1st jump, then work on up to 100psi final reading.
9x outa 10, its burnt valves that lowers your readings way down below 100psi.
Usually its only one exhaust valve that burns before you can't seem to get that 'miss' at idle to go away.
150psi on any motor is a good reading. It says the rings and valve are in good working order. :icon_bigg
According to online TSRM, your numbers are fine. As long as you're above 140psi I think. When you start dropping below that is when you might want to consider a freshen up.
Guys, don't forget that a compression test must me done when the motor is warm, AND!!! you must have the fuse pulled for the fuel pump. You do not want the injectors spraying fuel into the cyliders during your test because this will raise your compression and give you a false number.