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New camshaft - fit bearings or not?


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The block from my 2500S is currently stripped down and due to be refreshed with a re-bore, crank regrind, new bearing shells etc. My stock camshaft is OK with a little bit of wear so I haven't decided yet whether to replace it with a new Chris Witor or Newman shaft, or keep using it, given that I'll be doing fairly low miles and nothing competitive in it.

If I were to replace it, can I just run a new camshaft on the old bearing surfaces in the block? Is there any benefit to having these bored to fit bearing shells? 

Also, a couple of people have offered me good used camshafts - does this change any advice relating to the above? My gut instinct would be to avoid something that's already been worn in to a different block.

I presume with either option the cam followers should be renewed as a matter of course? Mine don't really show much wear and if I reuse my existing camshaft I'll just stick with these.

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No factory built 6 cylinder had cam bearings. The cams run direct in the block material. This is mostly fine and they survive well. Damage is caused by very poor/dirty oil, lack of oil, sustained high rpm In combination with big cam lifts. Also excessively strong or coil-bound valve springs.

If the block cam-way is in good condition, for a road engine there is no very good reason to go to the trouble and expense of having it line-bored for bearings.

Likewise, there should be no issues fitting a new, reprofiled or good used cam, provided the bearing journals are good.

If you do need/want to get the block line-bored for bearings, you use the Mk3 Spitfire bearings. Biggest problem is finding a machine shop with the kit and skills to do the job properly as it is a long, narrow hole. Has to be done in one pass from one end. Avoid anyone who says it can be done in two hits from each end.....

Cam followers: Ideally use new regardless, but if the original cam is going back in the same block and the followers are in good condition with their original position is known, that can be reused.


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Cheers Nick and Pete - good advice.

I was thinking about this last night and think I'll do this one properly with a new camshaft, will probably just run on the existing bearing surfaces as they seemed OK to me. Can always ask my machine shop to give them a glance too.

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