I received a diagnostic from a shop that bank 1 timing is off by 1-2 teeth. I have asked for a quote but was curious if we had anyone in here near Lakewood, CO or anywhere in the Denver area willing to do a chain replacement and what your labor rate would be. I would like to supply the Ford OEM parts and a Melling M360 oil pump.

I would also like to ask a question about compression. The shop said cylinders 3,5,7 (which they compression tested due to misfires) had higher than normal compression. Would the timing have caused this or is there another underlying issue that's causing this high compression? I appreciate anyone's feedback and attempt to help me with a quote.

 

Yes, if the timing is off one way, it can cause higher than normal compression.

 

Thank's Roadie! I know it's so the shop is protecting themselves but they're already hinting towards a new rebuilt engine due to the high compression which they're saying could mean bent valves and if you redo the top end you need to redo the bottom end, yada yada, and I just don't think it's necessary so I appreciate that feedback.

I read somewhere else someone saying if a valve was bent there'd be low compression. Not sure of the validity of that statement though.

 

It's true. If the valve is bent, it won't seat completely and the compression will be low or noexistent.

 

It wouldn't hurt to borescope the cylinders just to make sure, and pull the valve covers to look for cam and follower issues.

If they check out, do the job right - replace the entire VCT system, chains, tensioners, and guides. Clean the junk out of the oil pan and clean the pickup screen.

 

On cylinders 3,5,7 - because timing is off 1 or 2 teeth on bank 1?

Not aside from the bank/cylinder problem I have with that, how can timing off (any direction) actually result in compression being higher. Or was the mechanic saying 1,2,4,6,8 were 'not' as high as 3,5,7?

I agree with the bent (or burnt) valve theory if it isn't 'high'. And I agree with borescoping (or further diagnostic) and if necessary doing the job right - replace everything.

 

If one side is stretched, the other side probably is too.

 

They are not just trying to protect themselves. They are trying to play you for a fool. And you've already beat them at that game. There is nothing (related to timing) that will result in compression being an ounce higher than normal under perfect conditions. A non-compressible liquid in the cylinder (water or oil) is the only thing that would cause compression test to give a 'high' result. If that were the case - same recommendation - run like hell from that mechanic if he didn't figure that out instead of telling you it was a couple of teeth off in timing. You are right on what you read - and like @Roadie said, a bent valve would result in 'low' or 'no' compression.

 

Agreed, compression can never go up, only down

 

You guys are wrong. There are posts on this forum about the 4.2L V6 having high compression numbers due to the timing chain slipping due to worn keyway.

 

With all due respect to ALL my fellow forum members - posts don't make it so.


A turbo or blower acting up could increase compression - but even variable valve timing functions to 'reduce' compression by retarding intake valve opening (thus regurgitating a little exhaust gases) and wasting a few cubic inches of downward stroke needed for drawing in max breath of air.


Over advanced of valve opening (up to piston contact) would just belch a little exhaust into the Intake manifold - and then close before piston bottom inhaling a little less air than it could have to compress.


That mechanic, like so many, was speaking mumbo - jumbo and needs to be avoided at all cost.

 

So you are saying that advancing or retarding the cam timing has no effect on compression. Think about that.

 

NO! NO! I guess I didn't esplain myself in a suitably understandable way. Certainly EITHER advance AND retard will BOTH have an effect on compression.


For benefit of the OP's proper reliance on the mechanic's statement, I was trying to say how & why EITHER will have the same effect --- DOWNWARD from normal compression - but _NEVER_ upward.


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EDIT
W E L L. On further thought - in respect of this directive, we should further clarify "COMPRESSION - PSI?" or "COMPRESSION RATIO?"
I assume the mechanic was talking about Compression "PSI" - or his statement just got even stupider if he was talking about the Compression RATIO being higher than normal on cylinders 3,5,7.

 

Compression ratio cannot vary (see below). PSI sure can.

When testing compression PSI, "higher" or "lower" than "normal" is immaterial. You are simply looking for all cylinders being within 15% of each other. Cylinders lower than the others usually have head gasket, ring, or valve leaks. Cylinders higher than the others usually have abnormal combustion chamber deposits (will increase the effective compression ratio). I suppose valve timing issues CAN affect this, but this should affect all cylinders on the same camshaft.

 

It's also possible that the head and/or block has previously had some machine work done to it. Machining the deck or head surface removes material, which will raise compression ratio, and thus could also raise pressures