I sent a list of questions about cams and lifters to a friend who
works in engine engineering at a major diesel engine manufacturing
company. He talked this over with his friends and following are the
message and two replies. Nothing earth-shaking, and some we may not
agree on, but this is what the people who do it for a living say.
>uncle jack
Gary --
The question being discussed on the Triumph list at the moment is
whether or not it is important to replace the lifters to the same
lobe after a rebuild.
Sooooooooo............I have a series of questions, and they really
should be answered by someone who knows, rather than us Trimph owners
with only opinions:
1. Should old lifters remain with old lobes?
2. Is it ever acceptable to use old lifters on a new cam? How about
new lifters on an old cam?
3. Is there any reason why an old lifter can't be reground to the
proper radius and reused?
4. Is Rockwell C hardness the only criteria for successful lifter life?
5. Is there anything wrong with just making the lifters out of good
steel and heat treating it to, say, Rockwell C 56 - 60?
Jack --
>We believe your cam and lifters are probably made out of chilled iron.
>That is a good thing. There are very hard carbides in the surface of
>both the cam lobe & lifter surface. The RC should be around 70. The
>amount of carbon in each is close to the same which allows them to live
>together.
>
>If you tried to use steel and did HT to RC 60 on the lifters the cam
>would eat them alive in very short order. Probably what you got
>imported.
>
>If the lobe surface and follower surface looks shinny and smooth, then
>leave them alone. Match them back up to each other and use them again.
>
>If you have to regrind the lobe, use a new follower.
>
>Always use molybendium disulfide in large amount when rebuilding.
>
>DO not regrind followers, they may not be designed to be flat and even
>if they are it is too easy for all but an expert in this process with
>chilled iron to have micro cracks develop and your in trouble in short
>order. Buy new ones done right, pay the little extra and have a happy
>valve train.
>
>So to answer your questions.
>
>1) Yes, definitely
>2) NO & NO
>3) Don't do it. 98% chance you can't get it done properly.
>4) Heck no, see my discussion in my previous response.
>5) Everything is wrong with this idea, you will waste time, effort and
>have junk in short order.
uncle jack
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