230 M115 engine head need rebuilding? - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 09-17-2011, 02:34 PM Thread Starter
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Question 230 M115 engine head need rebuilding?

My (new to me) 1979 230C Coupe issues blue smoke ONLY at high speed when passing traffic.

The fuel consumption is goofy bad and I have a wee bit of blowback when I open the oil plug on the valve cover.

A compression test revealed 157#, 157#, 153#, 159# PSI from cylinder 1 thru 4.

Some of the valve adjustments are too tight to the cam lobes (I did not check all - only what was evident once I opened the valve cover box), but with no significant cam wear.

The inside of the engine has no varnish build up after 141,000 miles (211K kms) and there is evidence that the car has been serviced with AmsOil since forever.

I am going to assume that the valves have worn into the seats on the head, eliminateing the important valve lash and the guides are a little sloppy causing smoke at speed. Therefore the head needs rebuilding.

Can anyone agree, differ, tell me I am stuffed on my diagnosis or offer an opinion?

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post #2 of 3 (permalink) Old 09-19-2011, 01:02 AM
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Is it smoking under high engine load in any gear? If so, we would suggest worn bores and/or piston rings. Our experience has indicated that the test for valve guides is the bottom of the hill trick when you put your foot down again and you get the puff of blue smoke. Blow back tends to indicate too much positive crankcase pressures, once again combustion gases leaking past the compression rings into the crank case. Obviously poor fuel consumption can be many things, but also supports worn bore/rings. Pull off the head, all will be revealled. You could adjust all the tappets and see if there is a change. thanks CMRL
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post #3 of 3 (permalink) Old 09-19-2011, 10:21 AM Thread Starter
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Thanks for the comment CMRL.

I did not notice any smoke except @ high speed in top gear. I will have to run it out in 1st and 2nd gear range and see what transpires. Compression test came back at 153 to 158#.

I just replaced the transmission, but I am going to have to re-think the car now. Drop the money for the engine overhaul (top end at least), and still have underwhelming performance?

I am wondering how difficult it is going to be to slide a 420 driveline in it? Being that my differential will be needing attention at some point, it can be changed out at the same time.

I guess I have some research to do.
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