[DeTomaso] rocker arm adjustment

Charles McCall charlesmccall at gmail.com
Mon Jun 14 11:23:52 EDT 2010


All possible causes. 

Just to talk about point 1 a little but - you know that you can't tighten
the rockers sufficiently by just tightening the set screw, right? 

There's a little technique where you set the desired height, back off a
little bit, and rotate both the set screw and the outer nut (which adjusts
height) a the same time, which really cranks down on the set screw. 

An allen wrench won't cut it and your rocker arms will not be tight. 

Charles McCall
1985 DeTomaso Pantera GT5-S #9375
"Raising Pantera Awareness Across Europe"
http://www.poca.com/index.php/gallery/?g2_itemId=2323

-----Mensaje original-----
De: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] En
nombre de Paul - Home
Enviado el: lunes, 14 de junio de 2010 17:18
Para: detomaso at realbig.com
Asunto: Re: [DeTomaso] rocker arm adjustment

I can think of a few reasons why they could be loosening up.

1. the set screw is backing off
2. the cam lobe is wearing down
3. when initially setup, there was oil in the hydraulic lifter that has 
now bled away, ie the lifter was pumped up and now isn't.
4. the tappet pre-load was set hot and now is being measured when cold.
5. the pushrods are bending and now they are "shorter"
6. when the tappet pre-load was set the tappet wasn't on the base circle 
of the cam, but it is now.

You may need to mark your set screws.  It is easy to check the pushrods 
for straightness.

Paul
#9270

Justin Greisberg wrote:
> question for cleveland experts -- 
> 
>  
> 
> I have stock block, crane linked hydraulic lifters, harland sharp roller
rockers.  i adjusted the rocker arms by going one valve at a time with the
engine on a stand to be sure I got it just right.  when I recently changed
head gaskets, I noticed several of the pushrods were just a tiny bit loose,
as if I had set the rocker arms a little too loose.  i reset them all, and
next time I changed the head gaskets (dont ask) a few weeks later, I noticed
the same thing again.  i gave up and have run the engine a bit and it seems
fine.  any thoughts on the tiny-bit-loose pushrods.  (tiny bit loose means I
can spin them easily and there is even a tiny bit of slack in them.
normally when I adjust, I tighten the rocker set screw until the rod no
longer spins by fingers, and then 1/2 turn more.)  justin
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