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Going from stock 1.5 to full narrow body roller 1.6 ratio are guide plates needed on 1987 non-self aligning heads?


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2012-04-18 22:14:44
2012-04-18 22:14:44

The pushrod cup in the rocker arm is moved closer to the center (i.e. towards the rocker arm stud where the rocker arm pivots) on a 1.6 ratio rocker arm versus a 1.5 ratio rocker arm. You have to check for clearance problems where the pushrod goes through the head since it is moved slightly toward the rocker arm stud.

Comp Cams makes a tool to remove material from that side of the push rod slot in the head -- the heads have to be removed to do this as it requires you to use a drill and metal shavings are going to be created.

You can check this by putting the rocker arms on and setting the valve lash and then turning the engine over by hand while checking for interference between the pushrod and the slot it passes through in the head. Need to check all 16 pushrods for interference through the entire rocker arm motion by turning the engine over by hand and making sure the pushrod doesn't bind in the slot where it passes through the head. If there's going to be an interference problem it will be on the side of the pushrod toward the rocker arm stud. You should be able to check one pushrod at a time by simply turning the engine over until the rocker arm is in a position where the valve is closed, then screwing the rocker arm nut on and setting the valve at zero lash, then turning the engine over by hand while checking for interference as you slowly turn the engine over and run the valve through an open/close cycle. Repeat for all 16.

To compare just do this procedure with a stock rocker arm and look at the pushrod/slot clearance in the head as you turn the engine over, and then do the same thing with your 1.6 rocker arms and you should see the difference and be able to tell if there's going to be trouble.

My own advice would be to have a machine shop convert the heads from pressed in studs to screw in rocker arm studs with guide plates as a 1.6 rocker arm places more strain on the studs and pushrods and it's just a good upgrade to get rid of the pressed in studs and use screw in studs and guide plates. When a machine shop does this conversion they just drill out the original pushrod slots in the heads because the guide plate keeps the pushrod in line and the rocker arm centered on the valve and it's just makes the valvetrain much more stable and reliable. Downside is it costs money and you have to use higher quality hardened pushrods with the guide plates -- which is not a bad idea anyway.

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2, one in the front and one in the rear.


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