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Discussion Starter #1
I own a '89 5.9 cummins engine that I bought for rebuild and eventually drop into a project.

So today I opened up the engine and was able to take a good look at all cylinders. Cylinders #1-4 are flawless with cross hatching.

However 5 & 6 have cavitation on the the cylinder walls with #6 being the worst.

Question is what now? How much is too much?. Does this automatically trigger a trip to the machine shop?. I haven't measured, but compared to photos on the net, the cavitation depths is minor, but definitely there.

Any input or advice would be great at this point.

Cheers
 

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Selling 4bt & 6bt parts to all of N.America
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General rule is if you can feel it with your finger nail, it needs at min a hone. If hone doesn't fix it, then it is bore time.
If you need a bore, be careful going to just any machine shop, as spec for any cummins 3.9 or 5.9L engine requires a bore plate, torqued to head spec's to stress the engine while boring. Most machine shops don't have the heavy 2" thick cummins bore plate. No bore plate, then you get round holes at idle & oblong holes under heavy load.
 

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joestjean - Cummins shouldn't be susceptible to cavitation, as they don't have wet liners.

Having you been using heavy doses of SCA coolants without removing leftover SCAs every couple coolant changes?

You may want to remove your water pump & check for any pitting as well.
 

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Discussion Starter #4
Well I say 'cavitation' but I guess 'pitting' would be more accurate. Its just unfortunately there on the last 2 cylinders. And even then only on the front side.

I guess i was wondering if this was something that was acceptable to a degree given the good quality of the other cylinders.

I have sourced cylinder boring at $450 which is bearable, but I was hoping to buy a rebuild kit, clean it all up and put her back together.
 

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My guess those cylinders have had water in them at some stage. Rust pitting. If no sign of current rust it was run after the water was in there. A good hone may get you going. Have seen some horror cylinders that have run quite well with rust pits, grooves and scoring, BUT that was a case of needing to get it running as quick as possible.
May pay to get a machine shop to have a look and get their opinion.
Cheers Steve
 
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