[Healeys] Cam and crank gear timing update

Michael Salter michaelsalter at gmail.com
Sun Nov 11 07:19:55 MST 2012

Bill's message is missing a bit of information I think.
When #4 cylinder is "on the rock" you set the clearances on #1 cylinder...
In most 4 stroke engines, at the end of the exhaust stroke the inlet valve
opens before TDC and the exhaust valve closes after TDC .
that means that at TDC at the end of the exhaust stroke both valves are
open, at least partially.
As you move the engine back and forth past that TDC point the valve rockers
for #4 cylinder will "rock" i.e. one will open as the other closes hence
the term "on the rock".
When that is the case when #4 is "on the rock" #1 cylinder is at the top of
its compression stroke. At that point the cams (on the camshaft) for #1
cylinder are both pointing away from the lifters for the valves of #1
cylinder which is where they need to be for setting the clearances.

Michael Salter

I have body panels check here <http://www.netbug.net/blogmichael/?p=445>

On Sun, Nov 11, 2012 at 8:59 AM, <warthodson at aol.com> wrote:

> I understand the statement below, but I am not familiar with the term "on
> the
> rock". Does anyone know the origin & exactly what does it refer to?
> Gary Hodson
> -----Original Message-----
> From: WILLIAM B LAWRENCE <ynotink at msn.com>
> Subject: Re: [Healeys] Cam and crank gear timing update
> A point of clarification: when you set the camshaft to "on the rock" on the
> number four cylinder you are setting it so that both of  the valves on
> number
> four are closed. In other words you are setting it so that number four
> cylinder is on the compression stroke.
> Bill Lawrence
> BN1 #554
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Michael Salter

                         *I have BJ8 water pump kits!!*

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