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 fullnoise
Fahrvergnugen
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| posted on March 3rd, 2003 at 12:14 PM |
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Rocker Geometry.
Is it all about getting the tappet screw over the centre of the valve stem at half lift?
Or is the angle of the rocker arms a consideration.
I can get a stock tappet screw going through a nice arc on the valve stem and the rocker arms look quite level with the gasket surface on the head.
However if I use swivel feet adjusters the rocker arm screw is obviously longer to clear the head and the geometry doesn't look as nice. Sure the
swivel ball is always over the stem but the rocker seems to be at an uncomfortable angle compared to the gasket surface.
Does it matter what angle the rocker arms are on?
CYA, CT
[Edited on 3-3-2003 by fullnoise]
esratrams
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splitbusaustralia
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| posted on March 3rd, 2003 at 12:49 PM |
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It is all about having the screw over the centre of the valve stem at half-lift.
However, when you fit swivel feet you can't
in fact achieve this unless you shim the rocker
stands and/or shorten the pushrods?
Last time I built an engine with swivel feet
I think I ended up shimming the rocker stand
2 to 3 mm? (I think it was two shims each 1.2mm thick
per stand - this is on a reground standard cam... )
Rocker geometry was good, had enough adjustment
on the feet and didn't have to alter the pushrods (probably
would have to on hotter cam with higher lift.....)
You know about the adjustable push rod
for setting up
geometry/pushrod length of course?
RobK
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OvalGlen
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| posted on March 3rd, 2003 at 07:25 PM |
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and as an added benifit : you get maximum lift and minimum wear.
The aim is to get the rocker to pivot an equal amount
on each side of centre ,,,,,,, or half lift makes the
rocker at right angles to the push rod and valve.
Which probably equates to half lift and tappet centre line of valve stem.
I guess you have a push rod with a section replaced by threaded rod with lock nuts to adjust the length.
And using a dial indicator to measure the valve movement. Yeah.?
This set up is more fun than measuring and adjusting Combustion chamber CC's.
Regards,Glenn>
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fullnoise
Fahrvergnugen
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| posted on March 4th, 2003 at 09:29 AM |
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I had an adjustable pushrod but I couldn't find it.
I had 3 different lengths of pushrod handy and 1 seems like an ideal fit.
The stock tappet screw is flat against the centre of the valve at half lift. There is stil 3 or 4 threads of adjustment either way in the screw. If I
have to use up that adjustment I'll worry.
Thanks for confirming my suspicions guys.
CYA, CT
esratrams
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jeffh
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| posted on March 4th, 2003 at 11:35 AM |
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I have heard, but not done it yet, that when you convert to the swivel foot adjusters, that you need to grind off about 60 thou from the face of the
rocker arm where the adjuster screws in to make room for the swivel foot rather than just having it protrude further.
Jeff
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