Subject: Re: [Healeys] Cam and crank gear timing update

From: [email-masked]
Date: Sun, 11 Nov 2012 08:59:26 -0500 (EST)

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 <[email-masked]>
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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From: Michael Salter <[email-masked]>
Date: Sun, 11 Nov 2012 09:19:55 -0500

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, <[email-masked]> wrote:

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-- 
Michael Salter

                         *I have BJ8 water pump kits!!*
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From: [email-masked]
Date: Sun, 11 Nov 2012 18:17:37 -0500 (EST)

Mike,
Your description refers to #4 cylinder being at the end of the exhaust stroke
& at TDC both of #4's valves will be partially open.
But Bill's message refers to #4 cylinder being on the compression stroke &
neither of #4's valves are open.
In your scenario, we would be adjusting the valves on #1 cylinder. In Bill's
scenario we would be adjusting the valves on #4 cylinder.
I thought the discussion was about setting the cam timing!
Gary

-----Original Message-----
From: Michael Salter <[email-masked]>
To: warthodson <[email-masked]>
Cc: healeys <[email-masked]>
Sent: Sun, Nov 11, 2012 8:19 am
Subject: Re: [Healeys] Cam and crank gear timing update

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

-----Original Message-----
From: WILLIAM B LAWRENCE <[email-masked]>
Subject: Re: [Healeys] Cam and crank gear timing update

[email-masked]

--
Michael Salter

                         I have BJ8 water pump kits!!
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Archive: http://www.team.net/archive

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---

From: "David Porter" <[email-masked]>
Date: Sun, 11 Nov 2012 17:21:50 -0700

The original discussion was about setting the cam in worse case
circumstances. No marks, repositioned keyway, etc. And even then it was
trial and error at best. Plus or minus a tooth.
 Relative to adjusting the lash the beauty of this knowledge you now
possess, one can adjust the valves (from any point in the firing order)
without any extra rotations of the engine. 
dave

[email-masked]

Porter Customs   2909 Arno NE
Albuquerque, NM USA 87107
505-352-1378
1954 BN2  1959 AN5
Porter Custom Bicycles

cars:
 www.britishcarforum.com/portercustoms.html
gallery:
http://picasaweb.google.com/porterscustombicycles/PorterCustomBicyclesStuff

GO HERE: http://porterbikes.com/  nice pictures-fun facts-my world

Mike,
Your description refers to #4 cylinder being at the end of the exhaust
stroke

[email-masked]

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From: richard mayor <[email-masked]>
Date: Mon, 12 Nov 2012 02:29:15 +0000

When the valves in a cylinder are "on the rock" -- that means they are
"rocking". One valve is closing and the other is opening at the same time. You
can see the movement. When you see one starting to open and the other starting
to close  - at the same time, they are rocking,  as when you rock the engine
back and forth. And then you now know that the opposite cylinder is at TDC on
it's compression stroke.
You can also use this method to adjust the valves by following the firing
order and doing it when it's opposite cylinder in "on the rock".
Richard Mayor, BN7-466, Vintage Racer,  Portland, Oregon

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> From: [email-masked]
> Date: Sun, 11 Nov 2012 08:59:26 -0500
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