Main Bearing Sizes - Why is my case smaller?

[cunning plan]

So we are in the middle of slowly rebuilding the engine and tried to install the new 'Main Bearing Set' from JK:

http://www.justkampers.com/vw-t2-bay-window-parts/t2-bay-engine-parts/general-engine-parts/070-198-461-main-bearing-set-1200cc-1600cc-aircooled-engines-1960-on.html" onclick="window.open(this.href);return false;

It says that they are: 'Standard size bearings, fits all VW (upright - I think they meant flat 4 as VW did not make an upright aircooled) 1200cc-1600cc aircooled engines, 1960 - 1982.

I took my bus of the road years ago, but as much as I know, it is a standard 1600 engine.

Anyway, the new bearings are too loose in the case casting recess, they wobble around, yet the old ones fit mm perfect, flush, tight and do not move.

The new and old bearings are different part numbers.

So I am wondering if the case has been bored out for some reason and if anyone has seen this before?

Old Bearing

New Bearing

I found this excellent resource which seems to suggest that re-boring cases for repair is quite common, although, I have not had a chance to measure my case properly yet: http://61vdub.blogspot.co.uk/2012/01/bearing-sizes.html" onclick="window.open(this.href);return false;

Anyone have any idea what the situation is, do I just need larger bearings?

 

[megaaircooledvw]

Bearing sizes can be a nightmare,3 sizes to measure , case ,crank ,thrust,hundreds of combinations.

 

[dustrat]

Yes it looks like your case has been line bored and depends by how much as what oversize bearing you need.The best thing you can do is buy crankcase and crank shaft gauges from JK or Heritage and measure your case. Also measure the thrust end of case to see if thrust has been fly cut.The standard size where thrust bearing sits is 22mm.Having cases line bored is quite common on older cases because of wear. I line bore and fly cut all engines that I build.When ordering new bearing you need to find out if crankshaft is standard or under size ie has it been reground , if case has been line bored and to what size and if crankshaft thrust has been cut. Type 1 Beetle is fitted with upright engine as are Early Bay campers meaning that they have fan housing. Later campers have type 4 engine that is flat with no fan housing as cooling is different.
Robert

 

[cunning plan]

Thanks guys. arty0047:

Yes it looks like your case has been line bored and depends by how much as what oversize bearing you need.The best thing you can do is buy crankcase and crank shaft gauges from JK or Heritage and measure your case.

Can this be done with a Calliper measure or would it be too inaccurate?

Also, could I just source and buy the same bearings that were already in the case, going by part number?

Also measure the thrust end of case to see if thrust has been fly cut.The standard size where thrust bearing sits is 22mm.Having cases line bored is quite common on older cases because of wear. I line bore and fly cut all engines that I build.When ordering new bearing you need to find out if crankshaft is standard or under size ie has it been reground , if case has been line bored and to what size and if crankshaft thrust has been cut.

Thanks, good information.

Type 1 Beetle is fitted with upright engine as are Early Bay campers meaning that they have fan housing. Later campers have type 4 engine that is flat with no fan housing as cooling is different.
Robert

Ah, that makes more sense, I was thinking Straight 4, Flat 4 etc. Upright being related to cooling, makes more sense.

 

[megaaircooledvw]

A vernier caliper will work.

 

[cunning plan]

A vernier caliper will work.

Thanks for confirmation, I'll give it a good measuring when I'm next there.

 

[cunning plan]

So I haven't had a chance to measure the case as it's not here with me, but I do have the old main bearings and the standard new main bearings, so I measured them:

Old main bearings:
Inside diameter: 55.18mm
Outside diameter: 66.12mm

Standard main bearings:
Inside diameter: 55.64mm
Outside diameter: 65.69mm

Difference:
ID: 0.46mm Smaller than Standard
OD: 0.43mm Smaller than Standard

Old Thrust bearing:
ID: 54.87mm
OD: 65.46mm

Standard Thrust bearing:
ID: 54.87mm
OD: 64.96mm

Difference:
ID: The Same.
OD: 1.00mm larger.

According to the VWH website, the bearings are measured: Crank / Case / Thrust.

https://vwheritage.mobi/GB/#/GB/page.cfm?iPageID=2185" onclick="window.open(this.href);return false;

So I'm fairly sure the Thrust bearing is +1.0mm larger than a standard bearing, however, I'm not totally sure how to identify the Crank and Case measurements from the values I have?

I would assume the ID is the 'crank' measurement and the OD is the 'case' measurement?

Does anyone know? :?

 

[Trikky2]

Yes internal diameter will be the crankshaft size and outside diameter will be the case size.

Your old bearings would seem to indicate the engine was previously reconditioned and that case has been align bored to a larger size and your crankshaft has been ground to a smaller size than stock.

 

[dustrat]

Phone JK and explain your problem that you have ordered wrong bearings. Send them your old bearings and ask them to supply correct bearings. If you have not damaged the bearing you got off them they may refund you cost against new correct set.
Robert

 

[cunning plan]

Phone JK and explain your problem that you have ordered wrong bearings. Send them your old bearings and ask them to supply correct bearings. If you have not damaged the bearing you got off them they may refund you cost against new correct set.
Robert

I might do, depending if I can get the gears off again without damaging the middle bearing.

Yes internal diameter will be the crankshaft size and outside diameter will be the case size.

Your old bearings would seem to indicate the engine was previously reconditioned and that case has been align bored to a larger size and your crankshaft has been ground to a smaller size than stock.

Trikky!! Again, thank you! arty0047:

So with that information, I can say my case is:

Crank: 0.46mm Smaller than standard.
Case: 0.43mm Larger than standard.
Thrust: 1mm Larger than standard.

Allowing for a slight inaccuracy of the Vernier Calipers (or exactly where I was measuring / dirt etc etc), the closest measurements to the above on the VWH website would give the value of:

0.50 / 0.50 / 1.00

I am now 95% sure these are the correct bearings for my case and crankshaft configuration:

https://www.vwheritage.com/shop/bay-bus/111198475A/main-bearing-set-0-5-0-50-1-00-1-2-1-6/?crumbStartPage=1&crumbStartRow=1" onclick="window.open(this.href);return false;

That's logical, right? :?

I have learned a little more! :mrgreen:

 

[lhu128l]

It's a bit more complicated than just replacing like for like ....you need to accurately measure the crank to see if in tolerance .look for wear and scoring ...if any or out then it will need grinding again which will affect new bearings ....Same with case it may need a line bore and again with thrust .....it's not as easy as just replacing

 

[cunning plan]

It's a bit more complicated than just replacing like for like ....you need to accurately measure the crank to see if in tolerance .look for wear and scoring ...if any or out then it will need grinding again which will affect new bearings ....Same with case it may need a line bore and again with thrust .....it's not as easy as just replacing

Understood and good point, however I have checked the crank and bearing 'seats' for obvious wear, the crank seems in pretty good condition, along with the cam shaft.

The bearing seats seem fine, with only one having a very slightly raised part in the middle (just about feel-able with your finger), where the convex-side of the bearing has the recess for oil-flow.

I guess to be sure, I need to check that the crank is within tolerance by measuring it.

Although, I don't think the engine has done many miles since someone reconditioned it as Trikky has identified, I certainly didn't do many miles with it before I took my bus off the road to work on it, probably less than 500 miles!

From what I can remember, the engine ran OK when it was running, but most of the time it had a problem with stalling, which I would assume is head / fuel / air / spark issue rather than wear from a major component in the case. I wanted to renew all wearable components in the case whilst I had it all apart anyway, but as I say, there was no real need to open the case, but you know how it is when you have taken most of it apart already and you're curious..... :lol:

So, the plan was to simply replace all wearable components, set everything back up, seal it all, then rebuild the heads etc (which I think is what really needed doing).