look at these compression numbers (1 Viewer)

[Nemesis Gnat]

it sounds like a good procedure to me... i couldnt tell you why youd get a high number randomly... maybe someone smarter than us will chime in?

by the way, im now in the final prep stages of pulling the motor and doing a full overhaul of the motor itself and of other parts of the truck, all as a result of this compression test. when life gives you lemons, you put headers and a cam on it... details will be in my rotm thread

 

[Kief]

maybe

I did a compression test on a rig that I just bought but want to verify the way I did the test to make sure I did it right. This is the guide I used. What will a compression test tell me? — Yahoo! Autos

I took the plugs out and disconnected the ignition coil, place the tester in the cylinder(s) and cranked for a few seconds. I cranked it for about 3-5 seconds. With each sec the PSI seemed to jump up until it would not go any higher. All readings were above 145psi's but occasionally I would get a reading of 180psi. I tested that cylinder again and got a reading of 150psi. Am I doing something wrong?

What kind of tester? Screw in or push in ? I'm assuming that you used a screw in if you did it yourself..

You ideally want to see uniform readings from 140 to 160. I have an old rig that had 100#'s on a cylinder but still ran smooth and didn't really used much oil. Spec's say 140 at the lowest I think. 145 to 150 meets the within 10% range. While you are there you should check oil pressure too with a true pressure gauge and see what it does. I think you want 35 to 60 lbs. More than 10 or 15 at idle but I am not positive what spec is.
While you had those plugs out did you notice their condition? Compare them with the pics found in most repair manuals..

I helped a friend do an in-frame refresh at 195(or more)k (on a rig I sold him) due to a bad head gasket and it still had hone marks in the block and no noticeable ring ridge. It needed some valve work but aside from that the bottom end was still in spec. (.002 or better on rod and main bearings). If well oiled the 2f is one tough motor..

 

[klinetime574]

it sounds like a good procedure to me... i couldnt tell you why youd get a high number randomly... maybe someone smarter than us will chime in?

by the way, im now in the final prep stages of pulling the motor and doing a full overhaul of the motor itself and of other parts of the truck, all as a result of this compression test. when life gives you lemons, you put headers and a cam on it... details will be in my rotm thread

I can't wait for your ROTM.

 

[Nemesis Gnat]

well i already did the rotm, ill just add to it... but i think we're on the same page

agh i need a place to pull a motor! i hate living in an apartment complex!

 

[rover67]

do a leakdown test and see where it's leaking.

 

[alaska60]

The added oil tells me rings and not valve, as far as I know.

XXXXXXXXXXXXX22222222222!!!!!! That sucks!!!

 

[GLTHFJ60]

Yup, rings it seems. You can replace the rings and HG without taking the engine out, you know.....

 

[lehiguy]

On the test procedure, you should remove all the plugs first, use a thread-in gague, and hold the throttle wide open so the cylinder can fill. Then you will get a true reading. On these tractor motors, if they were all 120 or better, and fairly even across all six cylinders, I would run it.

 

[rfj62]

agh i need a place to pull a motor! i hate living in an apartment complex!

I feel your pain, I don't have my own garage either.

On the test procedure, you should remove all the plugs first, use a thread-in gague, and hold the throttle wide open so the cylinder can fill. Then you will get a true reading. On these tractor motors, if they were all 120 or better, and fairly even across all six cylinders, I would run it.

That's exactly the way I did it and got psi all above 145. Some old mechanic told me I might get higher compression numbers with a high carbon build up. Does that make sense?

The truck has 260k miles on it, runs good, but I am parting it out because of rust. I just wanted to make sure the rings are good before I sell it.