John:
The short tappet/long pushrod combination is about 1/8" shorter than
the long tappet/short pushrod combination.
The rocker adjusters will take up this difference without any
problem.
Your valve openning is not affected by the head thickness. So long
as you can get the valve adjustment correct with the rocker adjusters. (ok,
some subtle differences in geometry do come into play, but we are not going
there. It's insignificant)
As for the valve specs you found. AE who made the original valves
for the engine lists the following.
62-68 Part # Length
EX V3571 4.328
IN V3570 4.359
68-80 Note. 73 Intake valve is a different Part # (larger diam.)
EX V34352 4.328
IN V34401 4.359
The only difference in the valve design is the cotter groove. So no
worries there. I think the printed data you have is erroneous, or shows the
type of tolerance drift that causes migrains.
Put er back together and don't worry about it. Converting to the
short tappet/long lifter set up is pretty much SOP now.
Kelvin.
> -----Original Message-----
> From: John DiFede [mailto:JDIFEDE@cablevision.com]
> Sent: Tuesday, January 23, 2001 8:05 AM
> To: mgs@autox.team.net
> Subject: Cylinder Heads, Valve Train, and Exhaust Valves
>
>
> I am installing a new cam in my 18V engine, and this engine
> has an older style (pre 18V) head installed, with the later
> (short) cam followers and (long) pushrods. I've read that
> the 18V heads were of a shorter height than the earlier
> heads, so I am wondering what effect using the earlier
> (thicker) head with the later cam followers and pushrods has
> on the valve train. I'm guessing that my valves may not be
> opening as much as they would be if I was using the later
> style 18V (thinner) head.
>
> I've looked through my shop manual and I can only find the
> dimension for the earlier head 3 - 11/16" , the size of my
> cylinder head. Does anybody have the dimensions for the
> later head, and the lengths of the early and later cam
> follower and pushrod combinations? The Vicki Brit
> catalogue also lists different exhaust valve lengths. Were
> the valves different
> due to the change in height of the cylinder heads?
>
>
> Any advise , suggestions, or personal experiences would be
> greatly appreciated.
>
> John DiFede
>
> 73 MGB (with early head)
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