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rocker clearance

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twayne24365

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In te process of building the 440 for my 65 coronet, and ran into a problem. after i got the rockers setup and was checking pushrod length i noticed the rocker tips were not sitting on the valvestem. the rocker is hitting the retainer, should i clearance all the rockers or get some rocker shaft shims? they are new 440 source 1.6 rockers on a set of cnc ported stealth heads. had to do a good bit of clearancing for the pushrods already. photo 2.jpgphoto 1.jpgphoto 3.jpg
 
I would not shim the rockers as you may throw off the geometry. So carefully clearance the rockers without removing too much material. If a lot has to be removed then probably should get another set of rockers.
 
I think I would try new rockers before you machine them so you can maybe return/exchange them. You have put a bunch of money into those heads. Why skimp on the rockers?
 
Looks like longer pushrods would solve the problem. That would move the pushrod side of the rocker arm up a little higher, moving the rocker away from the retainer.
 
Garys1969RR said:
Looks like longer pushrods would solve the problem. That would move the pushrod side of the rocker arm up a little higher, moving the rocker away from the retainer.
Click to expand...

This is a joke right? If that would work he could just turn the adjuster screw down farther!
 
After thinking about this a little more, I realize you would need to move the rocker arm away from the valve retainer by shimming the rocker arm shaft, as was suggested earlier. And that may require longer push rods if the adjuster screw reaches its maximum distance. Then you may have valve train geometry issues as Meep Meep said. Does anyone know how to solve this problem other than shimming the shaft or replacing/modifying the rocker arms? I guess a shorter installed height on the valve stems may work too, but that seems like a lot of trouble.
 
This all depends now on how the roller sweeps the valve tip at the present time (part of the rocker arm geometry).

If the pattern allows it............

Shimming the shafts (bandaid approach) may work. If the valve locks were designed for them you could use lash caps. It looks as if there is enough adjuster for the lashcaps which are generally .080" thick. So with a 1.6 rocker the adjuster would have to be backed off about .050".

Without changing the geometry.........

You can use a different retainer/spring diameter combination. The Comp Cams tool steel retainers are thinner, but could also change the installed height.

Depending upon the spring pressures one could change the locks. There are 10 degree locks available at -.050" installed height that would push the retainer down away from the valve tip, but, also increase the spring pressure. On a standard hydraulic flat tappet spring -.050 locks would increase the installed and open pressure about 15#.

Perhaps combinations of the above?

Those appear to be inexpensive rockers (light duty use) and grinding on rockers is never a really good solution. It will increase the chance of failure.
 
image.jpgimage.jpgimage.jpgI ended up clearancing the rockers as my budget wont allow me to get a better set like hughes or harland sharp, turned out to be fine, the roller sits behind center of the valve stem so at mid to high lift the roller will see most of its life on center of the valve stem
 
Just make sure that when you clearance the under side that you make a smooth radius grind. No sharp edges and NO 90 degree cuts..
 
Stumper said:
Just make sure that when you clearance the under side that you make a smooth radius grind. No sharp edges and NO 90 degree cuts..
Click to expand...

sure thing, i smoothed everything out before putting them back on the shafts
 
While I don't think the clearance work was not the direct cause of this failure, you can see where the 90 degree cut created the weak spot.

SDC12033.jpg
 
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