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Discussion Starter #1
2 years ago engine starts blowing coolant out overflow, did bottle test, sure enough head gasket, took to private mech trained in cats, sure enough blown between 5 and 6, asked obout liner protrusion and he said only checks when overhauling an engine. The engine never did seem to run right, allways had a boost leak, now only 20k later its pushing coolant again(I only truck when I find decent paying short haul freight). Took back to same mech, tore it down, headgasket blown between 5 and 6 again, pulled liners this time, 4 5 6 have about 1 or 2 inches of (wear or corosion?) under the liner flange where it sits on the block, mech said I need to counterbore these 3 and three new pots. The engine has about 900k and doesn't burn any oil between changes. I'm leaning towards a 6NZ gold rebuild kit, is this the best option for this rebuild(I can't convince myself to use the 3 old pots even if they look really good). The head last time had a furrow burnt between 5 and 6, got sent out, fixed, shaved, pressure checked, had cracks between valves but not leaking and still not leaking, but I think I will put reman head on. Should I counterbore all 6 or just the 3 that need, and what should the protrusion be, I've read anywhere from .0045 to .006, but looking for advice. I have in this engine a 800 marine cam, 58's, stage 2 ecm, 4 core high eff rad and one of Kurt's turbo's. I am asking for help to fix this engine right so it does have to come apart again. Any and all advice or comments very much appreciated. tks
 

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I always recommend .005"-.006" protrusion. You should cut all 6 cyls. evenly, which means cutting the counterbores .002"-.003" less than the shims.
Another option, if the other three cyls. have no wear, is to machine the shims flush, and then using the .003" thinner spacer plate. I probably have cut a hundred Cat engines like this with almost no failures.
 

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Discussion Starter #4
Thanks guys, talked to a shop today and they're gona get back when they can come up to do the counterbore, it's good to know what to expect! :goodluck tks
 
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