I just sent this to the wrong list...
Sure, spacing the rocker shaft up is sometimes a "close enough" solution,
but the amount of shim needed depends on the rocker arm ratio. If the arms
are 1:1, the shim height would be about half the thickness removed from the
head.
However, spacing the rocker shaft up any amount raises the rockers above the
valves, thus tilting them and changing the geometry. More shim = more tilt.
The only way to maintain the geometry is to change the pushrod length, which
as Bob pointed out, is simple.
Karl
TC 6370
> John what was actually done back in the day was to install spacers under
> the rocker arm stands to bring them back up to height for the push rods.
> The spacers would be the thickness of the amount removed from the head.
> This restores the geometry of the rocker arm,.
> Dallas
>
> ----- Original Message -----
> From: "Bob Grunau" <grunau.garage@sympatico.ca>
> To: "Bob Howard" <mgbob@juno.com>; <gunnellj@athenet.net>
> Cc: <Mg-t@autox.team.net>
> Sent: Wednesday, April 22, 2009 10:17 AM
> Subject: Re: [Mg-t] Fwd: Shaved Head
>
>
>> John,
>> You should have no problem using the original or Moss 'long" pushrods.
>> But
>> why buy new pushrods? Check eack end of the pushrods to see if they are
>> loose, if loose, clean, compress and tig weld the end to the tube.
>> Adjusting screws will almost certainly take up the small amount shaved
>> off
>> the head. Short or long adjusting screws will work as you are in fact
>> shortening the screw/pushrod combination by 0.022" to accomodate the head
>> shaving. Bugger all.
>> I would not use two head gaskets unless trying to reduce compression
>> ratio
>> ( which you are not ).
>> Bob Grunau
>>
>> John,
>> Be of good cheer. When you get the rocker assy back in place you can
>> figure out the necessary length of pushrod. Once you know that, it's easy
>> to shorten a pushrod. Pushrods are really push-tubes with fitted ends.
>> One end can be pulled off and you use a "parting tool" in a lathe to
>> shorten the tube. When I rebuilt my XPAG a decade back, Moss was out of
>> the short pushrods, sent the long ones, and a friend shortened them for
>> me in a half hour.
>> Bob
>>>
>>>
>>> Hey Mates
>>>
>>> I am trying to figure out which push rods I need for my MG TD engine
>>> build. Or rather, in the "real world" situation, if I can safely
>>> still use the "long" push rods Moss sells. I say this because they
>>> no longer have the short push rods.
>>>
>>> The Moss catalog states the factory head depth is 3.022. The shop
>>> resurfaced mine. My mechanic says it measures out with a very slight
>>> taper, but within spec, and averages 3.00 inches. So is my head
>>> "excessively" thinner to the point where the "long" push rods won't
>>> work?
>>>
>>> Moss says that they now have only the long push rods. The rep told
>>> me that Crane is out of business and no longer making push rods. I
>>> checked Crane's Website. Sure enough. Today (April 22) they are
>>> auctioning off all their inventory, equipment and intellectual
>>> property rights. Since they make the T-series camshaft that Moss
>>> sells, I don't know the implications of this to the T-Series
>>> community.
>>>
>>> As far as my situation at present, I have the head torqued down and
>>> the rocker arm assembly has been sent to Rocker Arm Specialists. So
>>> I hope I do not have to go with two head gaskets and I cannot tell
>>> you is my rocker arm assembly has the long or short adjusting
>>> screws.
>>>
>>>
>>> John Gunnell
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