Rocker Arm geometry...
Thread Starter
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
Rocker Arm geometry...
So I am mocking up the assembly of my motor tonight, and I used a spare stock pushrod from the vette (not bent) and was playing around with the rocker arms. (1.6 roller tipped rockers)
Well, it looks like on the base circle of the cam the roller rests on the outside edge (not quite the edge really, but near that area) and then at full lift the roller sits about center.
So, I want this to actually go from edge to edge right?
That would be accomplished via correct pushrod length, correct?
Or is this adequate for a mild stroker???
(I have been given too much "advice" and need some sorting out!)
Sorry for the dumb question,
Thanks in advance guys,
Well, it looks like on the base circle of the cam the roller rests on the outside edge (not quite the edge really, but near that area) and then at full lift the roller sits about center.
So, I want this to actually go from edge to edge right?
That would be accomplished via correct pushrod length, correct?
Or is this adequate for a mild stroker???
(I have been given too much "advice" and need some sorting out!)
Sorry for the dumb question,
Thanks in advance guys,
Burning Brakes
Joined: Aug 2004
Posts: 1,110
Likes: 1
From: Geneseo Illinois
St. Jude Donor '06
Melting Slicks
Joined: Dec 2004
Posts: 2,137
Likes: 5
From: Howard PA
How does lifter pre load play into the geometry? Every tip says use a solid lifter, but most of us have hydraulic lifters that that require some amount of pre load, won't this change the pattern or is it insignificant?
Race Director
Joined: Feb 2004
Posts: 12,518
Likes: 19
I usually use the standard factory roller lifter for checking. The solid lifter is 1/2 inch shorter and cannot be used. I use a checking spring inplace of the correct spring. I adjust the valve as I would with the correct parts (preload) I then roll motor over and watch the valve tip.( I use a sharpie to cover the valve tip). The amount removed leaves an easy to view pattern. The middle 1/3 of the valve is the goal. If the wear mark is centered, and measures .060 or less, you are real close or perfect.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
The interesting thing about rocker geometry is that even the big name companies can't agree. Some will say that it is extremely important to center the contact while another says that it doesn't matter if it is perfectly centered as long as the contact patch is as small as possible (thereby eliminiating excess lateral movement)
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
I use a factory OE lifter that is modified so that there is no movement in the hydraulic parts. I also install a light valve clearance checking spring in all cases to check for geometry. This also allows one to use whatever lifter they are using virtually without risk of the lifter guts bleeding down when rotating the engine over. If the lifter bleeds down then you are left with an inaccurate measurement.
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Originally Posted by tjwong
I use a factory OE lifter that is modified so that there is no movement in the hydraulic parts. I also install a light valve clearance checking spring in all cases to check for geometry. This also allows one to use whatever lifter they are using virtually without risk of the lifter guts bleeding down when rotating the engine over. If the lifter bleeds down then you are left with an inaccurate measurement.
I also use the light spring as well
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Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by USAsOnlyWay
So I am mocking up the assembly of my motor tonight, and I used a spare stock pushrod from the vette (not bent) and was playing around with the rocker arms. (1.6 roller tipped rockers)
Well, it looks like on the base circle of the cam the roller rests on the outside edge (not quite the edge really, but near that area) and then at full lift the roller sits about center.
So, I want this to actually go from edge to edge right?
That would be accomplished via correct pushrod length, correct?
Or is this adequate for a mild stroker???
(I have been given too much "advice" and need some sorting out!)
Sorry for the dumb question,
Thanks in advance guys,
Well, it looks like on the base circle of the cam the roller rests on the outside edge (not quite the edge really, but near that area) and then at full lift the roller sits about center.
So, I want this to actually go from edge to edge right?
That would be accomplished via correct pushrod length, correct?
Or is this adequate for a mild stroker???
(I have been given too much "advice" and need some sorting out!)
Sorry for the dumb question,
Thanks in advance guys,
INBOARD with the lifter of the base circle;
CENTERED with the valve at mid-lift and
OUTBOARD at full lift.
Seems that the pushrod you're using is too short.
Rule of thumb: it's always better to have pushrods that are a little too long than ones that are a little too short.
Jake
Thread Starter
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
Thanks everyone, I am going to get a solid lifter and attempt it again. I believe the hydraulic lifter actually compressed which caused it to act as if it was a shorter pushrod.
I don't understand how a decked block with 64cc heads could require a longer pushrods when I know of several people running stock lenght pushrods on their motor with these heads.
I'll update as things progress.
I don't understand how a decked block with 64cc heads could require a longer pushrods when I know of several people running stock lenght pushrods on their motor with these heads.
I'll update as things progress.
