Thanks for the help Bob. When I was doing my comparison of valve lifts I was
turning the engine over using the starter motor, so hopefully the lifters
would have not leaked down too much. To measure the lift I used a block of
plastic that is a press fit on a steel rod. By placing the rod on the valve
cover mating surface, and adjusting the block so that it touched the rocker
arm (with the valve closed), when the engine was turned over the block would
be pushed up the rod by the rocker arm. The block would remain at this
'maximum' position due to it's fit on the rod. I could then measure the
distance with my trusty steel ruler. I repeated this for each valve. This
didn't give me the lift of each valve, but I was able to compare them with
each other. As mentioned the spread was less than 2mm between all of them,
which seems ok to me (although I'm looking to avoid a teardown at this
stage).
All a bit crude I agree, but I was looking to see if any one lifter was much
worse than the others - general opinion seems to be that camshafts wear
unevenly, and that a worn lobe would stand out like a sore thumb.
As I said, I'd like to avoid too much work and expense on the engine at this
stage. By the time I replace the cam, timing chain lifter, and get the heads
re-conditioned I'd be looking at about $2000 NZ. For probably only 1.5 to 2
times this I could get a rebuilt engine, so I'd rather save up for that.
I will replace the timing chain though, I have the gaskets required, and a
roller chainset is only about $180NZ.
Simon
-----Original Message-----
From: Bob Wilson [mailto:wilsnfam@cadvision.com]
Sent: Wednesday, 7 April 1999 09:17
To: simon.sparrow@wang.co.nz
Subject: Cam Lobe Wear
Simon: ref: my reply to you on the MGB V8 BBS...I was thinking of solid
(mechanical) lifters/tappets in describing how to measure cam lobe lift and
detect wear.
If you have hydraulic lifters, the technique of measuring valve lift is not
foolproof, as hydraulics in less-than-perfect condition can leak off fluid
in the absence of oil pressure, (you are turning the engine slowly, by
hand) and give apparent valve lifts less than they would with the same
lifters operating with full oil pressure.
The only way I know of to measure lobe lift (hydraulic lifters) with the
cam in-situ is to measure movement of the BODY of each lifter. This
eliminates errors due to leakdown. As you know, on your Rover, this would
require removal of the intake manifold (and valley splash pan/cover if
there is one). You must use a dial indicator for the measurements to have
meaningful accuracy.
Remember that intake and exhaust lobes may have different lifts as part of
the camshaft design.
good luck..and replace that timing chain soon!
Bob
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