Hi Keith...
You message indicated .278 lift at the cam... this would most likely
indicate a re-ground cam, as the stock fed spec. TR6 cams only had about
.232 (early) lift at the cam...
For those that care, you can arrive at this number as follows:
Stock rocker ratio: 1.42:1 == .704
Lift at valve: .330 (early TR6) or .340 (later TR6)
Cam bump == lift at valve * .704 == .232 (early) or .239 (late)
The numbers you quote are quite a bit more than that and would equate to
roughly .394 lift at the valve.
Ergo - you have a regrind in there.
And it's worn.
Now, you left out some important infomation. Presuming your rocker shaft is
intact and the head is on the motor... there's not much you can do.
You should yank the head and check the lifters.
Chances are you have either a bad lifter (the lifter will "take out" the
cam lobe and visa-versa) or a bad cam lobe. In either case, the news is
bad. Time for a new cam. And lifters.
Once you yank the cam out of the block, there will be numbers and letters
ground onto the cam somewhere... depending on what numbers you find, you
can determine exactly which regrind you had. When the regrind takes place,
the shop doing the job usually obliterates the original Triumph part (the
familiar 6 digit number) and either stamps the number on one end of the cam
or re-writes it with an electric pencil on the cam shaft section itself.
Either way, you're about to part with some money.
I'll give you some advice - do the job right and you'll be all set for a
long time... do it not right and you'll be doing it again _real soon_.
I know one guy that got only a couple of hundred miles out of a regrind
because either the cam of the lifters were "soft".
Pay the extra money and do the job right.
Oh - and the most important part of doing this job is to break in the cam
"right". Do it wrong, and the cam/lifters are toast. Do it right and they
should last a while.
regards,
rml
TR6's
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