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TR6: Indexing the Piper270 cam, part 2

To: Triumph List <triumphs@autox.team.net>
Subject: TR6: Indexing the Piper270 cam, part 2
From: Rob Christopher <robc@cisco.com>
Date: Wed, 12 Jun 2002 11:41:43 -0400
Hi again everyone,

Based on the responses from my first question on this topic (thanks to
everyone Hugh, Randall, Bob) I had another shot at the cam last night
using 'Method 1', crankshaft to 112 ATDC, find max intake lift on #1 and
chain together.

Now, the question is how close is close enough.  I am using the original
cam sprocket so I have the 1/2 tooth adjustability using the two sets of
holes, and there is some slop in the bolts holes on the sprocket so
there is a little adjustment there as well.

Using the 'centreline' method in the cranecams.com document Hugh pointed
me to, I get the following results:

1st set of holes, moving the cam within the slop of these holes, I can
achieve 104 to 109 ATDC for max lift on #1 intake.
2ns set of holes, moving the cam within the slop of these holes, I can
achieve 114 to 117 ATDC for max lift on #1 intake.

Note, neither of these gives me the 112 ATDC the spec calls for.  So,
which of these two would be the better choice?  109 ATDC or 114 ATDC?  I
think as the chain stretches, the 109 would slowly become 110, 111...

Should I just drill a new set of holes 1/4 tooth away from the others?
Create a little more slop in the current holes?  Or stiffle my
engineering gene that won't allow me to accept 'close enough' and bolt
it up at 109 or 114?

Rob
74.5 TR6  CF28217UO  (now on the 5th hour of indexing the camshaft....)

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