Puzzled by main bearing issue

[minirailz]

Hi!

By the end of last summer I decided to rebuild an engine, for the learning proces and also to have a spare on the shelf.

I try to do it by the book, replace or refurbish, depending on the state of the materials.
I'm doing a mostly stock 1300 F-block.

I send my case over to Germany to get it alignbored by Ahnendorp, an aircooled engine rebuilding specialist.
They decided to bore the case to +1.00, thrustbearing -1.00 (21mm), the new CSP crank was balanced and kept it's STD measurements.
Bearings were supplied by Ahnendorp and are silverline.

When installing the main bearings, the thrustbearing at the flywheel is a really tight fit.
When closing the case, using the 6 M12 bolts, the crank binds to the case.
The bearings are not pinched or blocked by the dowel pins...
(because I already pinched my first set, so learned that the hard way )
I did try without the pins, but no difference.

When using the trick to set the other half of the splitted main bearing on the crank, while installed in one case half, it has about 0,7mm of slack.
Way too much. There's no slack without the last bearing installed.

So it seems that the thrustbearing is not aligned with the other bearings.

Question now is: how do I proceed, what can I still test to confirm or fix this?
Could it be a warped case or would that have been noticed during alignboring?

Any advice much appreciated!!

Thanks!
Dennis
ps: sending the case back to Ahnendorp is a costly business, so I can't just jump in and ask them to take a look.

[Glenn]

[modok]

I can talk about it all day, literally, but it's up to you to decide what to do about it.
This is in response to many similar questions over the years.
https://www.thesamba.com/vw/forum/viewtopic.php?t=777121

[mukluk]

Have you checked the crank to see if it's bent?
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1960 Ragtop w/Semaphores "Inga"

[SGKent]

It must spin freely using something like SAE30. Use a plastic mallet or something to tap the bearings into the case. Were it me at this point I would have the crank gear off to make it easy, then try it with #2 and #3 main. See if it spins freely or not. If not try #2 and #4. If it does then you know it is #3. Try to see if they are all tight or just one. It sounds like someone screwed up either doing the cutting, or with the bearing set. You can also spin it with the bearings in one case half to see how it feels. It could be as simple as they sent the wrong bearings. On the back of the bearings there should be marks that show what size they are.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[modok]

Some people believe the thrust bearing should be a near zero fit in the case front to back.
I don't agree, but it can be done and work fine IF done right.
To make it a tight fit and still work you will probably need to freshly machine both sides to below a half thou runout, which is not easy and not typical.

I commonly find several thou runout on the thrust faces most engine blocks, including these old VWs, and the bearings are similar.
I think the reason some people THINK it needs to be a tight fit is because they don't actually check anything or have no way to check it except by feel and it feels tight to them.

Not saying this is the problem, but may help explain whatever you find if you measure the thrust width of the engine case all the way around, which you might do based on what you said so far.

[modok]

I prefer to first bolt the housing together and check the size of the bores, BEFORE checking the alignment of the bores.
This lets you check all the way around AND tell if deviations from straight is difference in size VS alignment.
Would be rare to have an alignment problem on a freshly lined bored case, check the sizes and bearings first.
Checking the squareness of the thrust surface is rather difficult and I don't have a easy way to do that. It can be done lots of ways but you should never need to do that. Probably set it up in the machine you'd use to fix it and just check it that way, because then it could be corrected if it's too far off.

[minirailz]

Thank you all for the replies.

I think the crank is straight.
When not bolted down it does turn quite alright, without any differences in resistance.

The thrustbearing shows wear on the bottom left and top right of the inside.
Confirming that the crank is in on an angle.
It did a little math, it seems the crank is 0,1mm higher in the split-bearing if the thrustbearing is mounted. So that last bearing is probably 0,15mm too high/out of round...

Since this is my first build and I asked an aircooled specialist to do the machining, I didn't bought a micrometer to measure the inside of the bores.
I was expecting them to do a good job and/or let me know if it was off.
I might have to acquire such micrometer now I guess...

If the case is warped, would that be my responsibility or would that have shown during the alignbore-process?
I checked the webbing inside and no light comes through...

Dennis

[modok]

I don't think you fully understood what I have said so far about the squareness of the thrust faces, but....if you want to keep going....
Try it with just #1 and #3 bearings, & check the bearing thickness and housing sizes (aka case holes)

the #1 has to be aligned to the main seal and the transmission centering ring, so that would be how you check it's alignment.
#2 just needs to be-in line with the bearings on either side, which you can check with a straightedge in the bores.

So IF the crank spins with just #3 and #1, then put an indicator on the crank and indicate the bellhousing surface and main seal bore, if you want to see if #1 is in the right spot or not. Perhaps check the gap around the pulley seal bore to see if that is centered also.

[txoval]

Also, since it’s your first engine build…#1 bearing is the thrust bearing…#4 is by pulley.

Just want to make sure you know

Also, at what torque does it bind? You should check at each interval 10, 15, 20, 25

[minirailz]

OK understood, it's the #1 that is causing me trouble, I think.
I haven't checked yet at what torque it binds. It just get's tougher and tougher I guess. It still sort of moves when it's almost torqued down...

@modok: thank you for the extra information.

I will visit a local engine builder next wednesday, I feel I need some physical advice/help.
Also he has plenty of tools I don' t have to measure or correct the cut, as far as possible of course.

Since I assembled the cam gears, I'm currently unable to remove the #3 bearing.

I tried it before without the #2 bearing, that gave the same result as with all the bearings mounted.
I only feel it's seating properly without #1 and it also turns very smooth in that setup...

I will keep you posted on any progress!!

Dennis
ps: results are same in both case-halves

[johnnyvw164]

In the "Bergman Bomb" thread an issue came up where the #1 crank journal had a very slight taper towards the end opposite the flywheel...might want to check that, just in case.

[Dusty1]

[minirailz]

The above is very true.

IF I warped the case, or it was warped before, I will definitely ask for a new linebored case.
I want a fully assembled short block, it's just a pain and costly affair if you're like me and having not enough experience to get it right...

Dennis

[minirailz]

Ok, so I went to a local VWAC engine builder to have my case checked.
(I wish I knew him before I went to the German firm)
It appears the line-bore on the #2 was not done exactly straight.
He made a bit more room on #2 and made sure the #1 bearing fitted correctly by machining a little bit off.

Apparently this firm I choose to have it alignbored is known for doing it in 2 stages. 1 or 2 bearings from one end and then they flip the case and do the other side.
Not sure how much of this is true, but it would explain the minor offset.

Afterwards we closed (and sealed) the case together so I can continue my build.

Bottomline:
1. If you go to a aircooled specialist, for premium engine works at a premium price, that's no guarantee it is indeed as good as advertised.
Nevertheless I believe that they still provide good end-products...

2. Rebuilding an engine is fun, but the case/bearing/crank alignment is so critical, it might be worth letting a pro do this particular work.

Thank you all for your advise and wisdom.
Wish me luck on the oncoming challenges

Dennis

[nsracing]

did you check the bearing crush? Use a dialbore gauge and see how much crush on the bearings.

Not all linebore jobs are created equal. You get what you pay for -

[minirailz]

The crush was not measured unfortunately.
I guess this only applies on the split bearing?

I payed top-dollar (top-euro?) for a linebore by an experienced well-known ACVW/Porsche tuning company.
I guess they just blindly bored and returned the case.
If you buy a full engine, they figure out themselves it needs more machining I hope...

Dennis

[Clatter]