orwell84 Samba Member
Joined: May 14, 2007 Posts: 2539 Location: Plattsburgh, New York
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Posted: Tue Apr 13, 2021 5:14 am Post subject: Re: 1800cc Type 4 engine rebuild - 74 westy |
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white74westy wrote: |
raygreenwood wrote: |
orwell84 wrote: |
I did the whacking thing with the thrust bearing which allowed the cam to turn freely. The endplay was still a little tight so I used a sharpening stone to adjust it a bit. I think I tried about 4 different sets of bearings. The reground stock cam I used fit fine. Maybe the webcams are a little tight. Sanding thrust bearings seem to be SOP with aftermarket cams. |
Not really.....not until you have seated it in. Don't sand the thrust bearings until last resort. The cam needs to be rapped pretty sharply...and in both directions.
Make sure the case is buttoned completely up...all bolts...not just the six big ones.
Rap it fore and aft. Turn about three revs....repeat. Take it apart and inspect.
Each time you put it back together...you will have to repeat at least the initial for and aft rap. The primary thing that is getting aligned when you rap it fore and aft....are the open legs of each bearing shell along the case centerline.
What happens is that they twist and squirm as they make contact with each other putting stress on on the shells as they warp.
Your cam thrust surfaces do look rough. Ray |
NOS bearings are on the way from Europe. I will do as you have outlined above.
Orwell84 - I guess I figured out where I'd read the rapping on the camshaft thing. Disregard the question in the PM. |
I wrote you a big long thing about it when I was on a plane, but haven’t sent it. It’s as Ray explains it, although I missed the part about buttoning up the case and it still worked for me. Following the above directions allowed the cam to spin freely and got the endplay just a little under the minimum spec. I probably could have run it like that but was afraid of it being too tight so it got a couple swipes on a 1200 grit sharpening stone to get it on the numbers. The thrust surfaces kind of flare outward out of the box and the rapping sets them parallel. A lot of times people just sand them to get the correct endplay, but then the thrust faces eventually end up aligning themselves after miles of running and the endplay opens up or at least that’s how I have understood it.
I think there are probably a number of factors that contribute to premature thrust bearing wear or failure. I think the one size fits all gear many of us end up using doesn’t help. VW went through the trouble of making many different gear sizes and they were not known for making things more complicated or expensive than necessary. The instructions in the books for checking a gear are pretty sparse. I’m sure the workers assembling these could do it by feel and really quickly too.
Anyway, keep at it. The above instructions did work for me even though rapping the cam gave me the willies. |
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