F250 compression #s

[formula29]

That sounds reasonable to me, I guess I need to take the vct apart and see whats inside.

[scofflaw]

advanced cam timing will increase cranking compression. Intake valve will be closing earlier beginning the compression stroke sooner.

The purpose of the Schrader valve in a compression tester is so the multiple compression strokes needed for the psi measurement can accumulate in the gauge. Got nothing to do with reading at your leisure or letting air out of the gauge.

[formula29]

I am actually focusing on the vct right now, thinking about it anyway, since the yds shows it is +12 degrees advanced(this is the port bank with higher compression) and it is supposed to be around -2 at idle I was wondering is the advanced intake timing is causing higher compression on the port bank, rodbolt said it should be around 2 degrees but nobody has mentioned what could be the problem, I have the motor all put back together and was going to quit on it but the advanced cam timing is calling to me, I have been searching for advance cam timing and find all contradicting stories, the service manual points out not to hold the camshaft itself when loosening the belt pulley or it will damage the vct,? who knows?

[TownsendsFJR1300]

My OTC DOES NOT have any schrader valves.

As shown above, plugs into the air compressor, plug in the hose to the engine. If the wrong size thread, there's adapters.

Now my compression tester (also OTC-separate unit) has a schrader valve to relieve built up pressure (saves the pressure so you can see it at your leisure).

Now I have used both on both 2 and 4 strokes. My 10 year old, OHV, 7HP B&S engine has a 3% leakdown rate at 100 PSI (which is really good for an older engine).

A small two stroke engine my neighbor gave me, ran real crappy, maybe 1/3 throttle had better than 130 PSI compression. Put the Leak down tester on, you could hear the air coming out of the lower end. Once broken down, the rings were found to be FULL or carbon and not sealing as they should. It should be noted that another small 2 stroke machine(not the same model) had approx 195 PSI compression. Anyway, I replaced the cylinder and piston from another parts engine, runs like a top now and is a spare...

Back to the engine,

Looking at the parts fisch, the one cam gear (I gather adjusts the valve timing with oil pressure??) is obviously very different from the other. Will that other "style/design" make a difference with the compression?

Static, everythings closed tight, but when cranking, (doing a compression test specifically), change?

[formula29]

I am not saying anything.

My comment regarding comparing tests was to 99yam. Not to you.

If the motor starts well, idles well, runs well, and appears to make rated power I don't see a problem. It was you that came here thinking that there was one. At least that is the reason that I think that you came here.

***! yes the reason I came here was to try and find out why one bank has 25 psi more than the other, to ask for some help determining the root cause, so it appears that you say as long as it runs decent and makes rated power there is no problem? I disagree,

[scofflaw]

Well I do, And mine didn't come with the hose that screws into the head. It's the same hose that also connects to my compression tester. Schrader in for compression test, out for leak down.

[99yam40]

He probably didn't remove the Schroeder valve

I do not own a leak down tester, so I do not know if they have Schrader valves like the compression testers, but I would not think so

[scofflaw]

He probably didn't remove the Schrader valve

[99yam40]

OK do you know anyone with a F250 that would be willing to do a compression test on the motor to see what they get?

which one is off the 195 or the 170?

I did ask if he listened for air leaking, no matter what the tester said
with 100psi on the cylinders you should be able to hear something some where even if it was very slight

[boscoe99]

Bosco99 have you ever heard of or seen yourself one or more of these motors having more compression on one bank?

No.

Have also never seen a motor that has 0 loss of air either.

[99yam40]

Bosco99 have you ever heard of or seen yourself one or more of these motors having more compression on one bank?

[boscoe99]

I don't see where I was comparing any tests? as stated from the beginning I am trying to figure out why one bank has 25 psi more compression than the other, for two engines to have the same values does not make sense to me, I did the leak down test as advised to eliminate valves not seating or blow by, so what is left boscoe? you are saying cylinder wear in the middle or bottom of the bore? just on one side of the motor? I guess if one side of the motor runs quite a bit hotter than the other it would be plausible, from what I know anything more than 15% between cylinders in not really acceptable,

I am not saying anything.

My comment regarding comparing tests was to 99yam. Not to you.

If the motor starts well, idles well, runs well, and appears to make rated power I don't see a problem. It was you that came here thinking that there was one. At least that is the reason that I think that you came here.

[99yam40]

maybe if that HF unit was not designed to run at 100 psi the volume of air is too great ,so the outlet pressure reads that high without it hooked up to anything.

Yes please do post what caused this if you find out.
and maybe someone will test another F250 and report what they get also

[formula29]

The air still has to pass through an 1/8" hole exiting the gauge, so that is a restriction that will build pressure, I'm done, I just reassembled everything and it still starts and runs, so at least I didn't break anything else, again thanks to everyone that commented on the thread, you guys are providing help and knowledge to people that need it, I know it can be frustrating trying to explain things to people but for me I would rather help guys out on the net than sit in front of the tv, I will post the outcome if the dealer finds the problem

[99yam40]

The leak down gauge is nothing more than a manifold with a regulator, as long as you have 2 functioning meters on it that's all you need, I have about beat this horse to death here, if its not a matter of a head gasket or wrong head I just don't know, time to take it back to where I bought them.

I agree if the valves and rings (cylinders) are all sealing then the only thing that could cause the different compression #s is size/volume of the combustion chamber.
head ,head gasket thickness, or piston.

I have read that some motors have different compression on different cylinders designed into the motors, but never heard of a whole bank designed that way.
We need someone else with F250s to run compression tests on their motors to see what they get to compare to.

Edit: just had a thought, what if you have over sized pistons on one side of both motors?

and I too though that reading 70psi without it hooked to anything is strange.
That should be 100% leakage