Align bore and bearings

[Mr Brown]

Hello all. I just got my 2.0 case back from a well known machine shop who did an align bore, crank grind and supplied the bearings. It took six months!

I was double checking the clearances today with the bearings in the case and noticed that the case was spread (can see light through the case halves) at the #2 saddle; the case through bolts were torqued to spec. Obviously the machine shop didn't check the fit of the bearings after the align bore. What are my options at this point? I thought about taking some material off the ends of the two bearing shells until the case halves meet. Anyone know what the crush dimension should be? I will measure the bore and bearing OD tomorrow once I calm down.

Also, I measure the #3 bearing/crank clearance at .004" which seems large and the #1 at .002, not very consistent. The bearings are Mahle .020/.020.

[RockCrusher]

DO NOT modify the bearing.....chances are the case is crap. Take the bearings out and torque the case empty and see if the gap is still there. That should have been check before they line bored it.

Let us know what you find.

RC
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[mark tucker]

hmm # 2 bearing,is that the split bearing?steel split bearing? just wondering.did you check to see if it is the correct bearing?? or was the case like that.

[RockCrusher]

Yes, #2 is the split bearing. #1 is the flywheel bearing and so forth. 99% chance the issue is the case.
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[email protected] Please use email for all general inquiries.

I will be happy to speak to anyone who has a serious inquiry (meaning real potential business for RC enterprises) or a parts order. Due to machining noise causing missed calls all calls will be returned promptly.

[mark tucker]

or bearing tang/pin.oops

[modok]

well now hold on a minute
The #2 steel backed bearing has extra crush built in due to it being steel

I have measured .006 crush, this amount WILL hold the case apart enough to measure with the bearing in there. Most people don't know because they never checked it. .006" does seem like too much, but I would not want less than .003"

You can sand the edges of the bearing some to tighten up the clearance IF you have more than enough crush, and sounds like you do.

[nsracing]

Oh come now, MOdok. Why would the #2 saddle have different specifications than the rest of the mains? I do not buy that for a second.

Do you set the linebore different for #2 bearings?

The split bearings do NOT have extra crush. They are bowed so they do not fall off the case-halves when pushed in place.

VW gave specs on the mains. YOu can measure the new bearings and I can tell you the bearing crush will vary 0.001 - 0.0025 inch.

The case split in there are likely from warping. This case is toast unless you have a giant flycutter and remachine the surfaces over.

[tencentlife]

Make sure the case saddle fastener threads are all chased clean, blown out and lightly oiled so you get the right torque. If not you can arrive at torque well before the case is pulled closed.

Then torque up the case without bearings, the mating gaps had better close right up for the flashlight test. Once you get them closed up, then you can accurately gauge the bearing fit, mic the bore ID's in that condition and compare to the average OD of each bearing. I look for crush to be optimally .002" difference between these measurements, but the real test is the working bearing ID torqued up in the case compared to journal OD, you won't have that true measurement until the gaps are completely closed up.

If the empty case accurately torqued up still shows gaps, might as well look for another case.
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[mark tucker]

just another reason I dont like the steel center main.

[HRVW]

When discussing the merits or results of a align bore case all have their own opinions for doing their particular way.

When building my engines I had three cutters (boring bars) 20/40/60 for my needs...already set up to use w/o having to remove the cutters off and on.

You can put the two halves together lightly and maybe see a little daylight with or w/o a flashlight. I always torqued my cases to 35lbs with a clicker before cutting and on assembly torqued the halves to 25lbs.

There will always be some difference of opinion am sure...we all have our results to deal with.

Generally I would first run a straight edge steel ruler across the main saddles before boring. At times would see a little daylight on #2 saddle but upon torqueing the halves together the daylight disappeared. Never had a comeback on my engines. Maybe my work was real good or just damn lucky.

Just my experience and opinion be what it may be.

[Mr Brown]

Thanks everyone! I rechecked the case today. Without bearings it closes up perfectly tight with little to no torque. With the #2 bearing installed and through bolts torqued to spec I measure a .004" gap above and below the bearing. The bearing is indeed bowed. If I hold the bearings together and measure the OD 90 deg from the split, it is actually smaller than the bore dimension; maybe it will eventually seat, though probably not before the bearing surface is compromised. I checked the bore and it is spot on for a .020" align bore. I think that if it was a non-steel backed bearing it would fit fine once the case was torqued, that steel is not going to budge. I also checked the bearing for out of round when installed and it was. I called the machine shop and they are looking for another bearing. If the bearing was just slightly less bowed, I think it would work. Maybe I could grease up the back of the bearing for another test fit to see if that helps it seat.

[modok]

[nsracing]

Now how in hell do you measure a split bearing for dimension when it bowed. Of course one across will be smaller and the other one across is way bigger.

But if you stick that split bearings in a round hole w/ proper dimension you will have the proper crush which is what VW has specified.

If the split bearing were perfectly round and split down the middle, you will probably not seat them in the saddles. They will just fall out. They are bowed so they will stay put and the "spring-back" is factored in there to give the proper crush when installed.

I set my boring bars exactly to 0.002 inch bearing crush. Exactly and I use a dialbore gauge to confirm the dimension. If you have way too much crush in the middle, there is no way in hell a gap will not show up.

[tencentlife]

^Agreed.

The full-circle bearings aren't round in your hand either (excepting maybe #4), so you mic the largest and smallest OD of each bearing and average the numbers, that is the true OD of the circle. The saddle ID is a true circle that should be .002" smaller than the bearing OD. Split #2 saddle isn't cut any differently.

The split bearing is indeed bowed to fit the saddle tightly, and because of that it may be impractical to calculate the average OD accurately because the two halves may be bowed to different degrees. But if the #2 holds the case open at full torque, and the other bearings fit their bores right and offer the right oil clearances when installed, the split shells can be filed off at the ends to attain the right fit.
_________________
Shop for unique Vanagon accessories at the Vanistan shop:
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Please don't PM here, I will not reply.

Experience is kryptonite to doctrine.

[RockCrusher]

[Mooosman]

[nsracing]

Modok must be too high up in Colorado and getting air-hungry.

You can measure true dimensions of a set of split-bearings but NOT the way Modok is describing. You cannot measure it free-hand.

You can bore a split-jig to proper dimension/roundness and use that to hold the split-bearings. The bearings will then follow the jig dimensions and you are free to measure.

[modok]

so you have done this?
BS
I've been putting off telling you because I know you would not believe it

This is the same as the distributor drive lash thing,
I figured it out in 10 minutes first time I built a type-4, but all you done is use your imagination

averaging the min and max does prove to be a good approximation of the actual diameter, and I know this because I have done it, I have clamped them round and measured the diameter and that is how I know this

[nsracing]

I will even give you a simpler way to guesstimate the dimension of split bearings.

All you need to do is measure the thickness of the bearings. Compare that to the other bearings. Assume the oil clearance is at minimum spec between crank journal and ID of bearing. If your split bearing has thicker material then you will know the OD of the split-bearings will be larger than the rest of the bearings.

Measure the thicknesses and find out.

Why in hell would VW insert a bearing set in there way oversized than the specified hole? If the saddles are too small, the split bearings will buckle! You ought to know since you rebuild rods. This is described in the Sunnen Engine REbuilding/Machining book which I would suspect your shop has one.

The #2 bearings having different dimensions does not make sense. We do not bore the center different than the rest. Nor do we grind cranks different in the center journal. If you are going to maintain the oil clearance between bearing and journal and you stick a larger diameter bearing in that hole, do you think you will still have clearance?

[modok]

mag/aluminum expands about 2 times faster than steel

if it had only .002 crush at room temp, what would it have at 250degrees F?


don't know?
I'll tell you, .0005-.001 CLEARANCE it would be LOOSE

is the bearing supposed to be loose? I don't think so