Dennis,
I'll bet there's nothing seriously wrong with the rockers, but if you did
indeed install new exhaust valve seats, there-in lies the problem. The valve
seats are not all at the same depth. All 4 of the seats need to be lowered
so that the distance between the face of the seat and the rocker is a little
less than the length of the new valve. They need to be as close to each
other as possible in length, so that the combustion chamber volumes are the
same. Once you've got the seats at the correct height (depth if you prefer)
you can than grind the valve stems to give you the required rocker/camshaft
clearance, AFTER you have set the eccentric bushes correctly.
There's nothing complicated about a MMM head but it is certainly different
from most. I've been playing with them since the mid 30's.
Cheers and Good Luck, "Bob".
> From: DENKLEMM@aol.com
> Reply-To: DENKLEMM@aol.com
> Date: Fri, 23 May 2003 14:40:16 EDT
> To: mg-mmm@autox.team.net, Mgbbk@aol.com
> Cc: bputnam@powercom.net
> Subject: MG PA Head
>
> Hi All,
> I've worked on a lot of different MGs and restored quite a few, but this PA
> is by far the hardest! Here is the problem.
>
> The head was cleaned, cracked tested and new seats and guides installed. New
> exhaust valves were purchased as the intake valves were deemed as good. The
> shafts of the intake valves are various lengths within a few thousands of each
> other.
> The exhaust valve shafts are all the same length as they are new. I assembled
> the cam shaft, rocker shafts and rockers (exactly in the same order they came
> off). The rocker bushings are set to they beginning position as directed in
> the manual.
>
> All of the intake valves are long (.006 clearance to the cam) by a few
> thousands. OK, fine they can be ground. The exhaust valves are short. #1
> cylinder by
> .070, #2 cylinder by .045, #3 cylinder by .20 and the #4 cylinder by .012.
>
> The machine shop is trying to tell me that the rockers are worn that much and
> that different. I sure cannot see that big a difference comparing #1 to #4
> rockers. Anybody got a clue as to what else to look for? Anybody got a drawing
> of a rocker?
>
> Confused and frustrated
> Dennis
> PA1518
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