What would you say is good/average compression on a T engine and at what point is it time for a rebuild?
45-55 psi is good for a std head T, when it's more than 10 psi difference between cylinders and/or if it's down to 25-30, I think it's time to check?
First check is to pour a little oil in the cylinders, if that makes a significant improvement you'll know it's the piston rings that isn't sealing good. If not much change but still bad, it's likely in the valves.
It's not sure you'll need a full rebuild just because the compression is low, a valve job may help a lot and keep you going for a few more years.
One of my winter projects has 35 on all 4 cylinders and I was thinking that might be a little low. Thanks for the advice.
Lonnie, If the engine has set for many years the compression will be low, maybe you should try firing it up once and let it run then check it, you may be surprised on the difference in the compression. Just a thought for you.
Always check compression with the throttle wide open too.
Count the revolutions you spin the engine and do the same on each cylinder.
Usually 10 will bring it up as high as it is going to go.
Altitude will affect the compression also, it looks like roughly 3% loss in pressure every 1000'