customer states flathead is leaking ALOT. So it is leaking badly out of the rear main seal area.I pulled the motor and found that the rear main seal has moved and there is about a three eighths inch gap. Okay That's the oil leak problem. I pulled the main bearing To check. And the rear main bearing is wasted, as is the thrust surfaces. The crank seems to be fine As far as gouging, but has a dark spot on one side.. It had very low oil pressure, but it was using the stock shoebox Ford gauges. It was rebuilt at some time as these are 10 under bearings. What say you? Toss in a new main bearing and good oil pump and let it go or tear down.
In the images, that crank does not appear to be "fine" at all. Looks like it needs to repolished at a minimum, and more likely recut to the next size under, depending on the geometry. In addition, it needs to get taken out and thoroughly cleaned to get all the bearing material out of the galleys.
If it was your own stuff, you could consider rolling in a new bearing and trying it. Worst case, you have to regrind the crank a 1000 miles down the road when it spins that main again. However, on a customer engine I wouldn't even think of rolling a bearing in and sending it, because if it returns in a 1000 miles with a spun main, you are rebuilding the entire motor for free then and adding one pissed off customer to the list.
I've let the customer know what's happening and I'm feeling out options. Why would the main bearing be wasted? But the other center and front main bearings be perfect? And the rod bearing is good too.
Looking at the images, especially the close up, it looks like the bearing started to delaminate. Possibly due to a manufacturing defect, possibly due to a crank journal that is slightly oversized and did not leave adequate clearance for the oil film. I also don't like what appears to be uneven wear between each side of the bearing, possibly pointing to incorrect journal geometry, or a bent crank. Journal bearing failure root cause is one of the most difficult things to identify because the bearing is typically destroyed in the process.
I wouldn't attempt any band aid fix on this one. You stated it had been rebuilt at some time in the past, but with the looks of the rear main I don't think it was rebuilt properly. At a minimum the crank would come out and be checked over carefully for size and out of round, also straightness.
I talked to the customer and he says whatever I think needs to happen. Go ahead and do it. So I think I'm going to pull the crank out. But the local machine shop has closed up. And I don't know anybody in my area That could check the crank and h and h flatheads is pricey And may take a long time. I'm in Lancaster, California, if anybody knows anybody at a machine shop close enough that knows what they're doing. Please give me a number or a shout out..
Not all that close but maybe Tim Mcmaster @mctim64 in Hanford? Probably doesn't do cranks in house but might know who to go to. Might even be closer to you. Just a thought.
I would trust Tim's advice but like you Said most machine shops for some reason Don't do cranks inhouse.
I think it might be worth the time to add an experience I had. The 8BA in my '51 started making a funny noise, I decided it was time to swap in the '51 Merc I had ready to install. It had good oil pressure, but was a little tired overall (low compression). When it came time to swap oil pans, I first removed the pan from the Ford engine. While cleaning it out, I came across a piece of triangular shaped metal about 1" X 1/2" in the bottom of the pan. Upon closer inspection, it was obviously a piece of the thrust surface of the rear main. I took it to my engine builder, and he confirmed that was what it was. When I asked how it could happen, he said probably a defective bearing. Similar problem, different manifestation?
To me ,it looks like the bearing shells were not fully seated or the rear main bore was not uniform in diameter. I'd clamp the rear cap on and check with a dial bore gage .
I turn the crank around a few times to see the worst part. And it seems to have chatter marks for lack of a better word.
Crank journal looks bad, that’s probably the cause. Make sure it doesn’t go back to whom ever rebuilt it last time.
Nobody has A clue who built the motor. I called h and h flatheads and left them a message and also an email with pictures. And I'm waiting to hear back from them.
Ive been told on more than one occasion that lugging an engine, shifting too soon, too low an rpm in too high a gear, will kill the thrust surface on the rear main. This inevitably sending bearing material through the oiling system and really making a mess. True? I dunno.
Well, Mike called me back and said basically The best way to go about this is to take him the whole motor. That way, he can check the caps on the block and check the crank. He says that there is likely something else fucked up in the motor causing just the rear bearing to be messed up. He also said just throwing a bearing in it Would probably get you by, but who knows how long
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