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Mikez73

compression test results

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My car hasn't been driven very much since I bought it last November..maybe 6 times total for less than 5 miles each time. It's been driven once in the last six months...about a one mile drive.

The previous owner rarely drove it. I did a cold compression test today. I figured this engine had high compression pistons but the piston, cam, and any other specs were known only to the original owner who is unfortunately no longer with us. Well, it has high compression on 4 cylinders LOL.

I'm not sure what to make of the results. Too much sitting up or sticky valves or both. Rings? Any thoughts?

1-185

2-200

3-100

4-195

5-185

6-115

I tried 3 and 6 again after a couple squirts of oil. 120 on both.

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Could be both. My original 70' Z motor was real bad, Less that 120 per and #3 and #6 were the worst of them all with barely 90 in each. That's why I pulled it and replaced it with my already rebuilt 2.6 liter. The 2.4 will be rebuilt one of these days.

Well, 3 out of 6 ain't too bad LOL

Dave

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Probably not rings, since the oil didn't bring them up much. I'd suspect sticking valves.

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Put some Marvel Mystery oil in the oil and gas and drive-a lot! All that sitting around isn't good for it. Get some real heat in the cylinders from some long drives and short ones too, then see what she does. I have been amazed more then once how these engines will come back to life. The marvel might help loosen the valves.

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You qualified the results by saying you did a COLD compression test:rolleyes:

With that, I would not get unduly concerned about the figures, since a meaningful CT is done on a motor at normal operating temp.

I'd drive it and see how it performs THEN, if you so desire, do an other CT when you get home, on a nice warm engine.

As an aside, low compression in #6 can be an indicator of a corroded head or damaged head gasket.

Since #6 is the lowest of the head and any sludge in the cooling system tends to attack the head and gasket at the lowest point.

Same happens to #4 in the L4 series and #4 in the FJ20 and.... I'm sure you get the pattern:ermm::ermm:

However a good quality coolant additive and regular use and periodical flushing of the cooling system is a good plan:bulb:

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Thanks guys but the carbs are off so taking the car out and driving it are out. I don't think it's that serious but that's just my opinion. The motor is strong and when I last drove it I could smoke the tires which seems pretty good for an L24 with 245/50 tires.

But when you're trying to sell a motor and the compression test says problem then it is a problem.

Thanks :cool:

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When you get it back together, if after a hot CT test you have the same problem, get a helper to keep the motor running and squirt some automatic transmission fluid in each carb. It's an old mechanics trick, but really works. Don't panic at the big white clouds coming out the exhaust! The fluid burns really hot and will burn off any deposits on the valves.

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When you get it back together, if after a hot CT test you have the same problem, get a helper to keep the motor running and squirt some automatic transmission fluid in each carb. It's an old mechanics trick, but really works. Don't panic at the big white clouds coming out the exhaust! The fluid burns really hot and will burn off any deposits on the valves.

Thanks Bob. They used to use that or water back before Seafoam right?

At any rate the carbs are not gong back on the car. Since I can't seem to sell the car I'm trying to sell the carbs, motor, tranny, header, gas tanks, etc and install an L28et.

EFI + turbo=happiness to me.

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