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MG TD TF 1500 - Mobius at the machine shop

I finally decided to go after the disease instead of the symptoms. I puled the engine and am having the cylinder bored out. They were at 0.040" and after a rough machining to 0.060" they sent me this note and the photo.

"The pictures we are sending you are of #4 cylinder rough bored to .060. As you can see from picture it didn’t machine whole cylinder. We still have about .003 to hone. We think it should be ok. May leave a small shadow. "

I told them to proceed and the honing cleaned it up very nicely.

I had suspected a lot of blow by resulting in excessive crank case pressure. Which of course manifested itself as oil leaks. What I found interesting and confirming is that the rough bore did not clean the cylinder. Therefore there was a substantial leak at least at that point and perhaps at other locations as well.

Currently waiting for custom pistons to continue the rebuild. More news later.

Mort

Mort 50 TD

It looks like you had it decked as well. Are the custom pistons because of that? Or to raise/lower the compression ratio. I seem to think your car is supercharged.
JE Carroll

MORT,
As long as you are this far, are you planning on a new crank??

Steve
Steve Wincze

Yes it is supercharged.

Steve,
We can find nothing wrong with the existing crank. The magnaflux was fine.

Mort
Mort 50 TD

Mine also magnafluxed fine,,, but I wanted to make sure that this was the last time I had to do any major work on/in the motor, so I'm going with a new crank,

Steve
Steve Wincze

Steve,
Where did you get one and what did it cost?
Thanks,
Mort
Mort 50 TD

Mort,
I'm going with a Moldex,, but as expected, it hasn't arrived yet. Price will be a bit more than Moss, but I will also have a bit more comfidence in it. I'll probebly try to sell my old one.

Steve
Steve Wincze

Mort, I would put in a Moldex or the MOss one. Know it is expensive but I blew and original crank useing a Judson, very expensive to do this twice. The original cranks in my opinion have a lot of spins on them being as they are 60 plus years old, made of old alloys or cast or what ever.My new engine is built to take a supercharger with new modern rods and pistons specifficaly designed to take the heat of a supercharger.Just my humble opinion, but if it was mine that is what I would go with. Nothing like supercharging but broken cranks are not fun.
TRM Maine

I'm finishing up an engine not unlike yours, Mort. It had been punched out to 1466cc about a half century ago and at .010" wall thickness (think about that), there's nowhere left to take it out to. Light honing is all that it'll tolerate. I had the new pistons knurled professionally- at $5 per piston, it saved me an afternoon of dinking around knurling them on my lathe. Cylinders definitely not abolutely perfect, but I expect probably 125++ psi compresssion across the board, imperfections and all. Your bore picture is better than any of mine, which have run for many years this way and will for many more.
Bear in mind, even with a large S.Co.T. blower, we're still talking about less than 20 hp per cylinder, about the same as a single cylinder garden tractor.
Moldex is only about 20 miles from here, and one of their masterpieces is going to spin us down the road for many years to come... it'll outlive us and the next bunch of owners, too. The roller lifter cam should outlast a few generations of owners, too. Wifey has promised our '50 TD "H. Mariah" to her great niece, so it'll stay in the family at least one genration.
I had blown numerous head gaskets, normally aspirated, years ago. Had the head milled, but the block was .005" low between cyls 2 & 3, so it came out a decade ago to get decked.
We had an outfit at a club meeting that "shot peens" goodies. I asked how much they'd charge to shot peen our TD's rods, and he said around $35. That sounded like it'd save me a bunch of aggravation doing it myself, so I dropped them off. Come to find out, that was $35 PER ROD. They look like they were just sand blasted as the number stampings show absolutely zero blemishing. Well that was $140 down the tubes.
Nothing like supercharging but broken RODS are not fun.
JRN JIM

This thread was discussed between 11/02/2016 and 24/02/2016

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