Re: [alfa] Dial Indicators for Finding TDC

["Daegrigg (Don)" <daegrigg@xxxxxxxxxxx>]

Having use both the dial indicator method and the pulley pointer method, in
my opinion the differences are moot and not enough to affect 99 percent of
Alfa engines.  Not a waste of time but perhaps not time well spent.

Don

----- Original Message -----
From: Ed Lutz <edlutz@domain.elided>
To: Paul Bayly <thebaylys@domain.elided>; alfa digest <alfa-digest@domain.elided>
Sent: Saturday, October 25, 2003 9:27 PM
Subject: Re: [alfa] Dial Indicators for Finding TDC


> You may find a bit of error is possible in using this method. this is due
> to the slowing motion of the piston as it rocks over TDC, it can be
> difficult to decide just where in the cranks rotation true TDC is really
> at. The most accurate method of determining TDC is probably (in my
opinion)
> the use of a degree wheel and piston stop. Mount the degree wheel as you
> would in timing cams. Insert the piston stop in the spark plug hole and
> turn the crank one direction until the piston stops on the piston stop.
> Record the reading on the degree wheel. Rotate the engine in the opposite
> direction and record the reading where the piston is stopped. True TDC
will
> be in the exact middle of these two readings. This method removes the
> "slop" inherent in the dial indicator method.
>
> Ed
>
> At 11:40 AM 10/26/03 +0930, Paul Bayly wrote:
> >Albert,  Good idea on confirming TDC.
> >
> >Most dial indicators I work with have some means of being attached to a
> >sliding rod, which in turn is attached to a clamp or magnetic base.
> >
> >Now obviously the magnetic base won't be any use on the alloy head, but a
> >suitably shaped iron plate simply held down across three head nuts will
> >suffice.This method would need a second pair of hands to rotate the
crank.
> >By using three resting points instead of four there is no rocking of the
> >plate. There will be very little force applied to the indicator by the
> >piston so variations in readings shouldn't present any problems due to
> >distortion of the dial clamping device/attaching arm.
> >
> >Alternatively, you could build some form of attachment using an old spark
> >plug, suitably hollowed out to allow the point of the indictor to feed
thru
> >onto the piston crown.  You may require an instrument with a longer point
> >than standard.
> >
> >The absolute value/measurement of the height of the piston relative to
the
> >top of the block is irrelevant, so is it's relative 'squareness' to the
top
> >of the block You are only after an indication of when the piston has
reached
> >the top of its travel, and you will be measuring the rotation over only a
> >few degrees as you rock the crank.  Once confirmed as correct, you can go
> >back to using the pointer on the front of the engine.
> >
> >Beatle
> >Oz
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