SKOOLS - rebuild advice needed

K

kamikaze

Junior Member
Skools:

I am thinking about rebuilding my 235 this winter (compression across each cylinder is currently 75 PSI. Compression was 95 PSI at start of the season).

I recently replaced the head gaskets and verfiied that none of the cylinder walls are scored, so my question is: Can I just hone each cylinder and replace the rings, Or do I need to bore and replace with over sized pistons. What would you recommend is the BEST way to go???

Thanks

Kamikaze
 
Skools:

I am thinking about rebuilding my 235 this winter (compression across each cylinder is currently 75 PSI. Compression was 95 PSI at start of the season).

I recently replaced the head gaskets and verfiied that none of the cylinder walls are scored, so my question is: Can I just hone each cylinder and replace the rings, Or do I need to bore and replace with over sized pistons. What would you recommend is the BEST way to go???

Thanks

Kamikaze
 
There is more to cylinder wear than scoring.  You need to measure the cylinder for taper.  Take measurements at the top middle and bottom of the cylinder.  All engines wear differently, most wear more at the top, a small block Chevy wears most in the center.  Wherever it is widest, if it's out of spec, it will cause premature wear of the piston ring grooves.  As the piston travels down in the cylinder, the ring expands and contracts to conform to varying bore diameters.  Excessive ring groove wear will lead to broken ring lands and piston rings.

If there is no ridge at the top of the cylinder caused by the ring wearing into the cylinder walls, you are generally safe to just hone. I still suggest you have the cylinders measured for taper anyways. Your engine will run quieter and last longer if you build it right.
 
There is more to cylinder wear than scoring.  You need to measure the cylinder for taper.  Take measurements at the top middle and bottom of the cylinder.  All engines wear differently, most wear more at the top, a small block Chevy wears most in the center.  Wherever it is widest, if it's out of spec, it will cause premature wear of the piston ring grooves.  As the piston travels down in the cylinder, the ring expands and contracts to conform to varying bore diameters.  Excessive ring groove wear will lead to broken ring lands and piston rings.

If there is no ridge at the top of the cylinder caused by the ring wearing into the cylinder walls, you are generally safe to just hone. I still suggest you have the cylinders measured for taper anyways. Your engine will run quieter and last longer if you build it right.
 
kamikaze said:
Skools:

I am thinking about rebuilding my 235 this winter (compression across each cylinder is currently 75 PSI. Compression was 95 PSI at start of the season).
Click to expand...

Isn't that odd that all six were 95 and now all six are 75??...
??? ...
 
kamikaze said:
Skools:

I am thinking about rebuilding my 235 this winter (compression across each cylinder is currently 75 PSI. Compression was 95 PSI at start of the season).
Click to expand...

Isn't that odd that all six were 95 and now all six are 75??...
??? ...
 
reelapeelin said:
Isn't that odd that all six were 95 and now all six are 75??...
??? ...
Click to expand...

Was the same gauge used both times? Was the engine cold one time and warm the other? Just a thought.
 
reelapeelin said:
Isn't that odd that all six were 95 and now all six are 75??...
??? ...
Click to expand...

Was the same gauge used both times? Was the engine cold one time and warm the other? Just a thought.
 
a 235 should have have around 120 each cylinder. you won't find a ring groove in an OMC the rings go to the top of the cylinder. This is an outboard not a 350 lol i've got several 350's with a ring groove and honed ran great. one the pistons would almost turn over in the cylinders but that motor made serious horse power. the looser the faster lol. This motor ran low 6's in a 1/8 milein a full body 78 camaro with A/C hooked up.
 
a 235 should have have around 120 each cylinder. you won't find a ring groove in an OMC the rings go to the top of the cylinder. This is an outboard not a 350 lol i've got several 350's with a ring groove and honed ran great. one the pistons would almost turn over in the cylinders but that motor made serious horse power. the looser the faster lol. This motor ran low 6's in a 1/8 milein a full body 78 camaro with A/C hooked up.
 
All:

Same compression gauge used both times. Believe me I checked. It would have been much easier if my gauge bit the dust than the option I'm facing. Warm or cold it doesn't matter - compression doesn't change. Don't forget the motor is 22 years old and has always given me great service. The only reason I'm think of rebuilding is the motor has only been in saltwater less than a dozen times and the majority of the ignition parts are brand new. For a basically about grand I'll be back in business

Skools : No need to worry about replacing the crank bearings unless there is an obvious problem?

Kamikaze
 
All:

Same compression gauge used both times. Believe me I checked. It would have been much easier if my gauge bit the dust than the option I'm facing. Warm or cold it doesn't matter - compression doesn't change. Don't forget the motor is 22 years old and has always given me great service. The only reason I'm think of rebuilding is the motor has only been in saltwater less than a dozen times and the majority of the ignition parts are brand new. For a basically about grand I'll be back in business

Skools : No need to worry about replacing the crank bearings unless there is an obvious problem?

Kamikaze
 
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