Piston scoring

[CAPTahab7]

I have a Merc 4.3 L on a 2003 Stingray. Ran acompression check and get values between 185,130,180, 95, 20, 120. The 20 and 95 psi are the #2 and 4 cylinders. I opened up and found:
scoring on #2 cylinder.
water in piston
my Q:
1) Do I need to get engine rebored for light scoring of cylinder.
2) Are 185 psi 'normal' for other cylinders (seems high)
3) Do I have leak in gasket (water in cylinder): scored cylinder coiuld not cause this could it?
4) Exhaust manifold have some light rust in them.
5) motor is low hrs (107), should I just be looking to get new motor or refab this one?

Advice sought!

 

[Aatcman]

Re: Piston scoring

Hi,

Hopefully we can get some of the guru's to chime in here....

It seems to me that you have mixed up some of your compression readings -- any fluid in a cylinder should cause the compression to go up -- not down -- by taking up space, it reduces the compression area, causing the compression ratio to go up.

As far as the scoring it's self -- depends on how bad the scoring is. At first, no. But if the cylinder is so badly scored that the scores go right through to the water jacket, then yes. Usually you will get water in a cylinder from other sources first, though. Likely candidates are rotted out or freeze damaged manifolds or risers, hard stops with bad or missing flappers, etc....

Look for rust trails or spots -- there should be a rust trail or spot where the water is coming in.

A rotted out (or blown) head gasket can allow water into the cylinder(s) too -- how did the head gaskets look when you pulled the heads?

How did the exhaust ports on the heads look? Rust there is an indication that you have water coming in from the exhaust manifold.........

Hope this helps!!

 

[Pete104]

Re: Piston scoring

You need to find a reliable machine shop in your area. Other poster is right, 185psi. Are you sure you didn't fill your gauge with water?

 

[CAPTahab7]

Re: Piston scoring

Traced this back to a blown head gasket. Thanks for the help guys!