Hi Bob,
Good idea, I've observed the pushrods spinning before but I'll take another
look this weekend to check they're all doing it.
I know what you mean about the 1.5-2mm being about 20-25% of total lift,
that was my thought as well. I guess I would be less optimistic if there was
only one or two lobes with this difference, or if I'd seen 4-5mm of wear.
I have no idea of the engines history, it came out of a car in a junkyard.
But last year it was dyno'ed at 120HP at the rear wheels, this is running on
LPG. The inlet and Exhaust system were quite restrictive at this stage as
well. As these engines (P76) where rated at about 190HP at the flywheel new,
it didn't seem too bad to me.
Simon
-----Original Message-----
From: Bob Wilson [mailto:emrmicro@cadvision.com]
Sent: Wednesday, 7 April 1999 11:41
To: Simon Sparrow
Subject: RE: Cam Lobe Wear
Sounds like you used a reasonable technique for your measurements. Bumping
the engine a partial turn every minute or so with the starter wouldn't
bring up oil pressure, so you may be seeing lifter leakoff rather than cam
wear.
Let's hope so, as most "mild" cam lobes have 6-7mm lift, so your observed
differences of 1.5 to 2mm could indicate 25% wear! This would mean the
surface hardening is long gone and the lifters are riding on the core
material (likely cast iron) of the lobes.
A way to tell is to run the engine at idle speed with the valve covers off
and observe the pushrods, which should all be spinning merrily. This
indicates that the taper which was ground into the lobes at "birth" to make
the lifters rotate, is still there, so they can't be worn very much.
Cheers;
Bob
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