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MG MGA - Bearing condition???

Well, I used a 10 pound slide hammer with a 1/2x20 threaded bolt in the bearing caps and they came out like a champ...seconds compared to how long it took me to get the rear cap off.

Anyway, several things of concern. 500 miles since the last rebuild and I two of the three main bearings have one "side," that is, one of the two flat surfaces on either side of the oil groove in the middle, are a gold color. The color of the bearing originally is silver, but these now have a gold petina.

I also removed the oil relief valve and it had some significant scouring on it. They were in the direction of movement of the valve, but the scours looked almost like when you clamp a vice grip on a bolt and it leaves marks.

Both of these issues make me a little more concerned about the fact that I always had 60-80 PSI of oil pressure (hot or cold motor, idle or at speed).

I felt the bearing journals on the crankshaft where the bearings had the gold color and they were a little rougher than a brand new crankshaft, but I didn't investigate further because I didn't want to get my feelings hurt...if that makes sense!!!??? Frankly, I'd like to take Suze Orman's advice from Larry King Live and invest my money in myself (as in my bank account) rather than spend the $600+ on a new crankshaft and bearings 500 miles after I already did the same!
J DeRienzo

Is there any evidence of "spun" main bearings? This would be, wear marks on the steel back of the bearing shells, wear marks on the bearing seating areas in the block and the cap, damaged or missing tabs that prevent the bearing shell from turning in the block.
Badly worn main bearings after 500 miles since new, excessively high oil pressure, and gouge marks from steel particles on the oil relief valve could point to spun main bearing shells. All these could result from the hole in the main bearing shell not lining up with the oil holes in the block.
As oil goes from the main bearings, through the crankshaft drillings, to the conrod bearings, what do the conrod bearings look like?

Mick
Mick Anderson

J. Sounds like residue from the oil has stained the bearings. A little shellac like varnish. Will it clean up with brake cleaner?

The color of worn bearings is copper as there is a copper base metal with some form of lighter metal applied over the base copper. Copper, has never looked golden colored to me.Thus, I suspect that it is a product of the oil, which I have seen in low use engines.

In addition to what Mick has posted, scratching of the bearings is always bad and can frequently be mated to scratching of the crankshaft journals. If you have scratching, you need to have the journals turned and fit the proper oversized bearings. If, however, the surfaces are smooth, I would not worry about it.

Mick makes a good point about using connecting rod bearings as an additional indicator. The markings on the oil pressure relief valve can only come from some form of grit in the oil system or some internal roughness in the hole in which the plunger operates. A through cleaning of the hole and an inspection can tell you if there is any roughness in the hole. If you had grit in the block, which made its way into the oil system, I would expect to see scoring on the main and connecting rod journals of the crankshaft--the mechanism is the grit embeds itself in the softer bearing material and cuts grooves in the journals. If that is not present, you may have had a minor bit of grit which was captured by the oil filter and did not affect the engine as a whole.

Do not know why you needed to tear down the engine at 500 miles, nor do I know how carefully the block and parts were cleaned prior to and during assembly. I find that the cleaning of the parts takes longer than the actual assembly process.

Les
Les Bengtson

To judge bearing condition a picture would be more than helpfull.
R J Brown

Oil stains/varnish definitely add up more than anything else.

To answer a couple questions... The reason I had to tear the motor apart is because the #11 head stud sheared in the block. After many green-type attempts at using a screw extractor, I got to the point where #1 I had to get a professional to extract what remains of the broken stud #2 A machinist to helicoil the hold #3 resurface the head and block because of surface rust on both mating surfaces.

The reason the first teardown was done was because of a #3 conrod spun bearing. I did not replace the oil relief valve (as I should have) because it seemed like the biggest issue with that valve was the spring being the right tension (which it was). The damage to it was probably from the first teardown where there was a bearing chewed and circulated through the oil system. I don't have that issue now.

Every conrod bearing looked perfect. The backs of all the main bearings also looked stellar and all the oil holes were lined up as I took things apart.

I would have taken pictures (I am not where the parts are), but due to time contstraints I had to give up on that, thus no pictures. This is the life of having multiple vehicles in multiple area codes...

Thanks for the fantastic input. I'll rub my fingers over the journals one more time before I start putting things back together, but otherwise I will hopefully be getting stuff back together for warmer weather. Thanks again!
J DeRienzo

Bearing journal surfaces on the crankshaft must be absolutely smooth to the touch, ground to almost a mirror finish. If you can feel any texture at all on the bearing journals, it has to be reground. The slightest roughness will eat up a new bearing shell with only a short time in operation.
Barney Gaylord

This thread was discussed on 25/01/2008

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