F250 compression #s

[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.

[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,

[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 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?

[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]

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

[TownsendsFJR1300]

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.

A shrader valve (as in your cars wheel) strictly holds air in (and more air as pressure allows) and allows you to release it.

And yes, when you push the valve in, it releases the air stored inside.

I guess we're playing with words today...

Sorry OP for the hyjack, but I'm on the same page as you with both engines, same banks, with the advanced timing are all the one thing in common..

Does the dealership have a variable cam engine (used, on a boat being fixed, etc) that you could do a compression test (for the high and low #'s) on EACH BANK?? Curious if another motor with that set up does the same.

One way or the other, you can make a more informed decision on what to do next...

[formula29]

I just got off the phone with a friend that has the same motor, he went out and scanned his motor and it was 1 to 2 degrees at idle on both banks so that confirms what rodbolt said about it being way off at +12 degrees at idle,

[TownsendsFJR1300]

So does that mean the cams are simply not installed correctly?

I worked on a small Yammy 40 HP maybe where the one cam was OFF TWO belt cogs and still ran good. We popped the belt off and the cam, on its own, jumped into the correct position.. (non-interference engine)

[formula29]

I have checked all of the timing marks, they are kind of idiot proof, I think either something is wrong with the cvt or it may be the wrong one maybe from an 05, I only say that because the port and starboard share the same part# but they look a little different, they have different markings on them. I need to go look at my friends motor tomorrow,

[TownsendsFJR1300]

Well, sounds like your narrowing it down...

Perhaps the dealer would replace both cams with new, correct ones...

[99yam40]

Did you not say that it all comes back into matching degrees at a higher RPM?
I am not sure how the ECU/scan sees the cam timing
Something is a problem at cranking or idle, but not higher RPM?

Seems strange that if the cam timing is off then the sealing of the cylinders would show a problem

I would try to find a different tester to try just to make sure

[formula29]

The ecm sees the cam timing through a cam position sensor, there is one on each cam, evidently the cam is advanced at cranking speed, the vct doesn't do anything until oil pressure builds up, so either the wrong vct pulley is installed or mine in broken and not letting the intake cam retard to its resting position, I don't know, I have never really had to mess with one of these so I will figure it out, there is in no way a need for another leak down test or new gauge, that will not change the timing,

[zenoahphobic]

I thought the leak down test was the cats meow. The be all and end all to solving problems.

For having 900 hours, a leak down test showing 0% loss of air is quite remarkable.

What is the objective? Is there a problem with the motor?

This is the issue when one does not fully understand one's instruments.

An "inappropriate" leakdown tester can easily show "0%" loss of air on quite a wornout engine!
I use the word inappropriate because each case must have the correct tester. If we assume the OP tester is operating correctly, but there is a chorus out there that says you must have some leakage, a scenario could be:
He has a large compressor that puts out lots of air easily at 100 psi.
His regulator responds readily to maintain that pressure.
His orifice (not getting personal) between the two gauges is also large allowing air to readily flow.
His leak is small or even a bit more (all engines leak).
His second gauge reads 100psi.
We are told this means there is no leak.
Nonsense, all it means is that the compressors air in the entire system can be maintained at 100psi!.
Air could be hissing out everywhere! But his tester doesn't pickup the leak because his orifice (not getting personal) is too large and/or the gauges orifices are too small acting with too much dampening restricting their reactions.
The only useful thing he has, if the above is true, are his ears. Listen for the leak(s).
Just a word of caution.

[zenoahphobic]

I have checked all of the timing marks, they are kind of idiot proof, I think either something is wrong with the cvt or it may be the wrong one maybe from an 05, I only say that because the port and starboard share the same part# but they look a little different, they have different markings on them. I need to go look at my friends motor tomorrow,

The variable cam timing on these engines was raised some time back. You may want to search past threads. Off the top of my head I think it was concluded there is no "serviceable" parts to it.