F250 compression #s

[TownsendsFJR1300]

Hey guys, I figured everyone was about tired of hearing about leakdown, differential, and compression test, I can laugh about it now. I bought another used vct pulley so I had a matching set and it is all good now, even compression all 6 cylinders, 170 lbs, and the intake cam timing was even on both banks as well @ plus or minus -1 to 2 at idle, The best guess I have is in 2005 and early 2006 they used the one vct pulley which added the timing and gave 195 psi at cranking speed, and I'm just guessing here that sometime in 2007 they switched to the latest vct pulley which yields 170 psi and basically no cam advance at cranking speed, and my biigest guess is that when these powerheads were redone there was one motor with the old pulleys and one motor with the newer pulleys and the tech mixed them up??

Interesting, glad you got it figured out..

[formula29]

Hey guys, I figured everyone was about tired of hearing about leakdown, differential, and compression test, I can laugh about it now. I bought another used vct pulley so I had a matching set and it is all good now, even compression all 6 cylinders, 170 lbs, and the intake cam timing was even on both banks as well @ plus or minus -1 to 2 at idle, The best guess I have is in 2005 and early 2006 they used the one vct pulley which added the timing and gave 195 psi at cranking speed, and I'm just guessing here that sometime in 2007 they switched to the latest vct pulley which yields 170 psi and basically no cam advance at cranking speed, and my biigest guess is that when these powerheads were redone there was one motor with the old pulleys and one motor with the newer pulleys and the tech mixed them up??

[TownsendsFJR1300]

Back to the thread, any updates Carmen??

[zenoahphobic]

I have no idea on how someone could do the same thing to two motors, but hell, the timing belts were on upside down too, I'm not quite sure how you do that, I bought them from a Yamaha dealer and I really don't think they did this to them, it probably happened when the powerheads were replaced, it would be nice to receive some sort of compensation sense they were sold to me with a clean bill of health, so far not so much.

I have not started the engine to see if the timing problem followed because I am not going to bolt everything back up until I get the right vct, but it had to follow, that is where the increased compression is coming from.

A good mechanic is consistent. Even a person who thinks he/she is a good mechanic but are not, can be consistent - that would explain the reversed belt and perhaps the placement of the cam sprockets, but it might be reasonable to assume the wrong sprockets were ordered or more likely came off a used (for spare parts) engine. What puzzles me is what was wrong with original correct sprockets, and of course what engine were these replaced off/for?

And Boscoe, Rodbolt might be in hiding, but it usually doesn't take much bait to get him to bite.

[formula29]

I still do not understand how/why someone would put one wrong VCT sprocket on the same side of both motors?
where did these come from?
they should not have come from the motors they took apart to repair.

A big question from me is, does the YDS show the cam timing problem the same on the other side now? just to verify that the timing problem followed the sprocket?
it should have if that is truly the problem


I am guessing you will be contacting the shop that sold you these motors to have the proper sprockets/parts replaced

I have no idea on how someone could do the same thing to two motors, but hell, the timing belts were on upside down too, I'm not quite sure how you do that, I bought them from a Yamaha dealer and I really don't think they did this to them, it probably happened when the powerheads were replaced, it would be nice to receive some sort of compensation sense they were sold to me with a clean bill of health, so far not so much.

I have not started the engine to see if the timing problem followed because I am not going to bolt everything back up until I get the right vct, but it had to follow, that is where the increased compression is coming from.

[99yam40]

I would have liked to see a leakdown test done with a known good tester to see if the cam timing at TDC
allowed/showed some leakage on one bank due to it being out of time
but that is just the way i am

[99yam40]

computer showed a problem, but someone( most of us) did not pay attention or did not know it was a problem.
Or what kind of problem it was
I have a hard time believing they did the same thing to both motors without it being on purpose

[boscoe99]

If the compression test is the proverbial teat on a boar hog, and the leak down test is the definitive be all end all test, how is it that the compression test showed a problem whereas the leak down test indicated there was no problem at all?

I be confused.

Mr. Rodbolt - We await your advice.

[99yam40]

I still do not understand how/why someone would put one wrong VCT sprocket on the same side of both motors?
where did these come from?
they should not have come from the motors they took apart to repair.

A big question from me is, does the YDS show the cam timing problem the same on the other side now? just to verify that the timing problem followed the sprocket?
it should have if that is truly the problem


I am guessing you will be contacting the shop that sold you these motors to have the proper sprockets/parts replaced

sorry i missed your last post on them not interested in talking to you.
too bad it would be intresting to find out how this happened

[formula29]

I am going to have to say the 170 psi is the correct range since that bank had the correct timing, the bank that had 195 psi had the 12 degree advance at idle, it made my morning when I switched the vct with each other and pulled another compression test and the numbers reversed, now to round up a couple used vct's, the dealer was not very interested in talking to me,

[zenoahphobic]

Since my problem has been solved I will oblige you here, although my HF home made gauge did hold 100 psi on the output side I could not hear any leakage through the intake runners or exhaust, when I removed the oil filler cap I could hear a slight air flow, probably a few psi that my gauge was not showing, I failed to mention it because we know where that would have went, I knew that the few psi that was leaking past the rings was not the problem I was chasing. In my case a simple compression tester was the first line tool in determining if there is a problem, then we move on to a differential test to further diagnose, there are multiple ways to go about doing things, I like to listen to all ideas and figure out what makes sense for me, even with the aggravation of the differential test experts, in the end rodbolt confirmed my intake timing was off and was not right, and that helped me to switch direction to the port bank being the problem, so it all worked out, thank you to everyone that participated in this thread!

Formula 29 I think you determined your intake timing was wrong. You haven't told us which one was wrong! the 170 or the195 one?

[formula29]

Point taken that too small to worry about, and quicker to do leakdown than compression test.

But I thought we had determined the leakdown test on this engine tells us nothing, so would you have then done a compression test? I infer you would not have! As the engine runs fine you probably would have told the customer the engine is fine! Logically you would not have had a reason to suspect anything wrong with the cam timing!

Sorry I see a little flaw following your postings, that's all.

That is a valid point, a leak down would have not shown the compression difference in my case, but what I just went through should have never happened

[zenoahphobic]

Point taken that too small to worry about, and quicker to do leakdown than compression test.

But I thought we had determined the leakdown test on this engine tells us nothing, so would you have then done a compression test? I infer you would not have! As the engine runs fine you probably would have told the customer the engine is fine! Logically you would not have had a reason to suspect anything wrong with the cam timing!

Sorry I see a little flaw following your postings, that's all.

Sorry referring to Rodbolt's last post.

[formula29]

if I tested 6 cyl's 4 were 5% or less and two indicated 0 then I would figure the leakage is to small for my equipment to measure and all is good in the hood and continue on.
this stuff aint hard if you don't over think it.
don't get hung up on stupid stuff.
remember that motor is actually 6 little motors that share a common crank and a common air intake.
if the compression test shows 195 on one bank and 170 on the other its FREAKING trying to tell ya sumptin ya think?

the next clue, the freaking cam timing IS NOT where it should be.
the cams should pretty much stay within a few degrees of each other at all times.

intake cam timing WILL affect compression.
it is NOT designed to have unequal compression unlike some 2 strokes of years past.

the compression test indicated a POTENTIAL [problem.
that needs to be looked at via a LEAKDOWN test.

now if it was your 100 bucks an hour,and its faster to do a leakage vs compression, would you like to pay for BOTH tests or just the more accurate of the two?

so that leaves did someone use the wrong parts that physically fit?
did someone reinstall a cam incorrectly?
did someone improperly shim the intake cam during a repair?

but something is wrong and its time to follow a logical rabbit trail.

not all throttles will open at just key on.
then you have to disable BOTH spark AND fuel.

Rodbolt, did you catch the part where I switched vct's from port to starboard and the compression #s reversed? I have two different vct's,, and on compression test I do remove the kill switch, however I do not disable the fuel,

[formula29]

Since my problem has been solved I will oblige you here, although my HF home made gauge did hold 100 psi on the output side I could not hear any leakage through the intake runners or exhaust, when I removed the oil filler cap I could hear a slight air flow, probably a few psi that my gauge was not showing, I failed to mention it because we know where that would have went, I knew that the few psi that was leaking past the rings was not the problem I was chasing. In my case a simple compression tester was the first line tool in determining if there is a problem, then we move on to a differential test to further diagnose, there are multiple ways to go about doing things, I like to listen to all ideas and figure out what makes sense for me, even with the aggravation of the differential test experts, in the end rodbolt confirmed my intake timing was off and was not right, and that helped me to switch direction to the port bank being the problem, so it all worked out, thank you to everyone that participated in this thread!