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cam bearing caps & worries about wear
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Author:  datajon [ Wed May 31, 2006 5:13 pm ]
Post subject:  cam bearing caps & worries about wear
i have a few cylinder heads that require some repairs :( , valve guides, re-facing no problem, but what about the worn camshaft bearing / caps.


a few choices I have.

1) line bore the old cylinder head camshaft bearings out to a suitable size, replacing with shell bearing, adding retaining plates to each set, possibly adding ball bearing races to the front for better support to cam wheels, have noticed that in some cases these particular parts sustain increased wear.

2) Purchase new bearing caps, BUT if like other engines, this is not as simple as its sounds, due to the high requirements for accuracy, replacements can often run out of line, can not line bore back to centre, this will cause an increase to clearance.

3) Purchase a new head, or a very good second-hand one that’s mint.

4) make my own replacement bearing caps ..



So the question is: :?:

would the cam bearing caps be inter changeable on a 205 cylinderhead with another head of the same type and part,& / or replace with new, without the problems of the camshafts running out of true, thus causing excessive wearing problems.


i welcome suggestions

thanks

Jon
Author:  Kris [ Wed May 31, 2006 6:18 pm ]
Post subject: 
I have wondered this Jon, since the bearing surface forms part of the head! It's not just a simple case as replace a shell, the head is actually worn! :(

Personally I can't think of any easy option, and iirc the BGB says, "simply replace the head" :shock:

I'll be interested to hear the solution :D
Author:  two_OH_five [ Wed May 31, 2006 7:52 pm ]
Post subject: 
Line bore and shell is the only way IMO

Can't see any other way

Give me a shout when you've perfected the process :D
Author:  datajon [ Thu Jun 01, 2006 11:11 am ]
Post subject: 
thanks guys, its a nightmare..got to sort something out, Mr T list price per head £1400...need 2..

nice £2800, before i even start.
Author:  Kris [ Thu Jun 01, 2006 7:14 pm ]
Post subject: 
In previous jobs I have had items spiral welded and then machined back...

could the caps/head be lined bored a little larger and the cams machined a little larger?

This would of course mean that "odd" cams would always have to be used in that particular head.

What about a custom cam from e.g. Piper? And then line bore the head to suit the larger diameter cam?

Probably a little too extreme and it would be easier to pick up a decent second hand head! :lol:
Author:  two_OH_five [ Thu Jun 01, 2006 9:17 pm ]
Post subject: 
You could also investigate having the head metal vapour sprayed to rebuild the original clearances

Just an idea, not sure if it's feasable
Author:  Terry_T [ Fri Jun 02, 2006 9:15 pm ]
Post subject: 
Machine a few thou off the mateing face of the caps and linebore back to standard,as the wear is usually in the cap as itr takes most of the thrust.Just my 2p this is what we do at work to recover a head if we can.
Author:  datajon [ Tue Jun 06, 2006 8:09 pm ]
Post subject: 
Hi Terry.

Quote:
Machine a few thou off the mating face of the caps and line bore back to standard, as the wear is usually in the cap as it takes most of the thrust


Yes a good idea, did think about it, only draw back i could see: some of the caps are used for thrust, they seem to show heavy wear. :(

I think the heads i have been neglected when used, hence why they are so bad.

Hopefully have suitable replacement parts now, just need to collect.. :)

Be calling you soon. Terry ……..TT upgrade..


Jon
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