Tight wrist pins
06-14-2011, 10:13 PM
#11
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Probably not going to help you out however in my younger days I learned the hard way. I was always one to be extremely clean on engine builds. This was before I was doing most of my own work I cleaned the rods and pistions in solvent just to make sure there was no debris etc. from the engine shop on the rods and pistons. I did oil them after cleaning however would have been better off leaving them alone the way they came from the shop. One of my new rebuilds locked up on the trailer breaking in the cam. I learned the hard way. The machine shop quickly figured what happened. Since then after assm (rods/pistons) I put them right in the oven at about 225 deg and work the red cam lube into the pin and piston. With the heat it just allows the oil to penetrate in much quicker and easier. Not saying this is your problem however just an old lesson I learned years ago.
Hope all works out.
Hope all works out.
Last edited by getrdunn; 06-14-2011 at 10:20 PM.
06-15-2011, 12:16 AM
#12
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What was the condition of the crank when it went into the build? Was it new, reground, used. How about the rods. Were they new? If used how old were they and have they ever been resized? Did anyone set up the clearence in the rod small ends with the pins.
06-15-2011, 07:46 AM
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well something was wrong...block not cleaned and crap got in the oil passages and restricted oiling...that also could have caused a overheat condition on the wrist pins..would not take long and may not have turned blue yet...bearing went 1st, crank not ground right..cleances etc...what oil pressure were you seeing before the knock ?
06-15-2011, 07:55 AM
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That would account for the bearing failure and the tight wrist pins...
In a higher HP marine application, I'll typically increase the pin clearance in the piston to .0012". Plenty of lube on the pins and pin bores is super important during assembly, and is often over looked. Tough to call at this point, with tons of debris in the oil from the bearing failure, as this will also contribute to the tight pins. I'd be looking closely for other signs of detonation, and at the tune up, as detonation may likely be the cause of the bearing failure and the pin issue.
06-15-2011, 08:05 AM
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The engine developed a knock rather quickly. We were moving along at about 3300 rpms. Trailered it and then pulled the motor to inspect. Spun a rod bearing on number 3. It was pretty bad and there was LOTS of metal in the oil and some pretty major chunks of metal in the pan. The engine guy totally tore it down today and it was noticed that the wrist pins were tight. Was it from the metal tainted oil, or did the pins tighten up due to tight tolerances and then take out the rod bearing. Hard to say what happened first. New crank, rod bearings, main bearings, oil pump will be here in the morning. It got a hot bath today and cleaned up very well. There was no block damage.
The engine guy could see no signs of any heat buildup at all in any of the parts, and he said that some of the areas that would be a telltale sign of an oil problem looked good. I am betting on the pin tolerances being too tight for a marine engine, but of course it is too late to be able to check them now. The cam and the cam bearings looked good, but we will be replacing the cam, bearings also. Of course we are also flushing the oil cooler and the remote oil filter lines.
The engine guy could see no signs of any heat buildup at all in any of the parts, and he said that some of the areas that would be a telltale sign of an oil problem looked good. I am betting on the pin tolerances being too tight for a marine engine, but of course it is too late to be able to check them now. The cam and the cam bearings looked good, but we will be replacing the cam, bearings also. Of course we are also flushing the oil cooler and the remote oil filter lines.
06-15-2011, 11:09 AM
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I appreciate all of the replies as we try to figure this thing out.
06-15-2011, 01:05 PM
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What other signs would there be of detonation? The g#d D@*%n thing is so loud that I cannot hear much, but the motor sure seemed to run smooth. Looking at the pipes (big tube headers cooled at the tips), it appears that maybe it was running a bit rich, if anything. In the limited research that I have done, detonation probably did not affect all cylinders, but I guess that it was possible to for it to happen to one, and then the shrapnel took out the rest?
I appreciate all of the replies as we try to figure this thing out.
I appreciate all of the replies as we try to figure this thing out.
