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2.1 WBX Crank Journal Measurements, Rebuild As Is?
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mbwesty
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PostPosted: Fri Sep 18, 2020 11:27 pm    Post subject: 2.1 WBX Crank Journal Measurements, Rebuild As Is? Reply with quote

Hi, I am in the processing of rebuilding a 2.1 WBX engine, and I can definitely use some serious input from those who had done this before.

So I spent the last couple nites taking measurements, and I had used a dial bore gauge and a mic to measure everything except for the smaller #4 bearing bore diameter. For the #4 bore I had used a snap gauge as my dial bore gauge only goes from 2-6".

Anyway, the case was cleaned by a machine shop, and the bearings and crank (came with the case) I had cleaned them myself. The bearings and case was then put back together and torqued back to spec per the Bentley for taking the measurements.

So here they are:

Crank Main Journals, no out of round and within the blue dot specs:

#1 - 2.3620"
#2 - 2.1649"
#3 - 2.1649"
#4 - 1.5746"

Rod Journals, within specs, I guess with some +/- errors like the rest:

#1 - 2.1651"
#2 - 2.1650"
#3 - 2.1654"
#4 - 2.1654"

Case with old bearings and clearances (basically, main bearing bore minus journal dia.):

#1 - horizontal=0.0028", vertical=0.0020"
#2 - horizontal=0.0041", vertical=0.0016"
#3 - horizontal=0.0036", vertical=0.0016"
#4 - horizontal=0.0035"

I guess I kinda found out that the main bearing clearance really wasn't an exact science as it was definitely not a perfect circle. I think taking the horizontal measurements was ok, but taking the "vertical" measurement was difficult and it could only be done at an angle because of the oil passage channel inside the top and bottom of the bearings.

I am thinking I should just get the crank send to a shop to get polished and then go buy a std. set of main bearings and continue the rebuild. So anyone think that perhaps I should go get some undersized bearings and regrind the crank journals for some tighter tolerance (like less than 0.003")?

oh, I am planning on getting some new rods and 2.2 P/Ls...thanks and appreciate your help!

Tim
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MarkWard
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PostPosted: Sat Sep 19, 2020 1:35 pm    Post subject: Re: 2.1 WBX Crank Journal Measurements, Rebuild As Is? Reply with quote

It would be nice to have less than .003Ē clearance. I would not grind the crank yet. It sounds like you were using used bearings? If so, I would try new bearings and remeasure.

Grinding the crank removes some of the outer hardness. Itís also a more complicated grind because the main journals are not all the same diameter. Youíd need a machine shop to really understand whatís needed.
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mbwesty
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PostPosted: Sat Sep 19, 2020 5:30 pm    Post subject: Re: 2.1 WBX Crank Journal Measurements, Rebuild As Is? Reply with quote

Hi Mark:

True and these were bearings from the engine when it was being disassembled. I was hoping it would gave me a baseline on where the engine was at since it was a donor.

Hmm...so no possible way to avoiding owning a set of new std. bearing to find out if a regrind is necessary? And is it common to have roughly a 2 thous difference between the horizontal and vertical clearance? And as far as the less than 0.003" clearance is concerned, is that for horizontal clearance as well? It seems that the bearings may be "ovaled" from the interference fit in the case...

I have a machine shop that's 20 minutes away that I can use for the polishing work, but for regrind I think would drop it off at DPR as they are like 25miles from me...decision time...

Thanks again for your help!


MarkWard wrote:
It would be nice to have less than .003Ē clearance. I would not grind the crank yet. It sounds like you were using used bearings? If so, I would try new bearings and remeasure.

Grinding the crank removes some of the outer hardness. Itís also a more complicated grind because the main journals are not all the same diameter. Youíd need a machine shop to really understand whatís needed.
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MarkWard
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PostPosted: Sat Sep 19, 2020 5:57 pm    Post subject: Re: 2.1 WBX Crank Journal Measurements, Rebuild As Is? Reply with quote

.003 is probably at the edge of the spec of new bearings. Used bearings would be acceptable. I donít build these engines, so I donít know the specs off hand. Iím thinking .0019Ē would be as tight as youíd want to run. So, your only out .001Ē of that. You almost canít measure that. I imagine new bearings would have the .001 your looking for. Then you have room to grind the crank next time. Iím assuming you are resizing the big ends of the connecting rods. That will likely tighten those clearances some.
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mbwesty
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PostPosted: Sun Sep 20, 2020 4:02 pm    Post subject: Re: 2.1 WBX Crank Journal Measurements, Rebuild As Is? Reply with quote

yeah, torqued the case back up and plasticgaged the #3 main clearance today, and the vertical axis clearance was 0.002". Close enough to the calculation from the mic/dial bore gauge. I think its good to go with a new set of std bearings.

Now, the strange thing was the cam clearance was way over 0.003"...hmm...what's going on here? I hope that with a new CAM and some new cam bearings it will be good to go.

Yeah, I am gonna get new rods and, if not, the big ends on the old ones will be completely re reworked.

I am also gonna go with AA's 95.5mm P/L as it was supposed to have the correct pin height...cool beans...

Thanks, Mark!


MarkWard wrote:
.003 is probably at the edge of the spec of new bearings. Used bearings would be acceptable. I donít build these engines, so I donít know the specs off hand. Iím thinking .0019Ē would be as tight as youíd want to run. So, your only out .001Ē of that. You almost canít measure that. I imagine new bearings would have the .001 your looking for. Then you have room to grind the crank next time. Iím assuming you are resizing the big ends of the connecting rods. That will likely tighten those clearances some.
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MayorMcCheese
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PostPosted: Sun Sep 20, 2020 7:00 pm    Post subject: Re: 2.1 WBX Crank Journal Measurements, Rebuild As Is? Reply with quote

.003 would be nice, but book specs are about .0045 max.
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