Rocker Arm Clearance

rickbtbird

Registered User
I'm a bit confused about the valve stem-to-rocker arm clearance. The book says it's .088 to .189. Then it says the Rocker arm fulcrum bolts have a two step torque sequence. So with that said, how is the clearance maintained? Do you measure it and adjust it after you torque the fulcrum bolt or do you use different size push rods to get the required clearance?
 
do you mean where the rocker touches the top of the valve stem ,thats at 0 , unless you've installed a different cam and they recommend a clearance

two step torque sequence ,to me means like - torque 15lbs then to 22lbs -for example

cheers
 
do you mean where the rocker touches the top of the valve stem ,thats at 0 , unless you've installed a different cam and they recommend a clearance

two step torque sequence ,to me means like - torque 15lbs then to 22lbs -for example

cheers

I'm talking about the valve stem-to-Rocker arm Clearance. If you look on page 2a of the Haynes (36086) book it's listed there. Then on 2a-6 it talks about Valve Adjustment and talks about using a bleed down tool and setting the number one pistion at TDC for some of the intake and eshaust valves and then rotating it 360 degrees and doing the others while making the value clearance adjustments. Then if you go back to page 2a-2 it list a two step torque spec for a for the Rocker Arm Fulcrum bolts.
I guess the question is, Isn't the Rocker Arm Fulcrum bolts the same bolts you would adjust for valve stem-to-rocker arm clearance?
 
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The stock rockers mount to the pedestal. There is no adjustment, just torque to spec. If there is wear you can adjust the tip clearance through the use of shims, but that could impact push rod length.
 
The stock rockers mount to the pedestal. There is no adjustment, just torque to spec. If there is wear you can adjust the tip clearance through the use of shims, but that could impact push rod length.

OK that's the answer I was looking for. The book also says the clearance can be changed by using different length pushrods "available from your dealer".. HAHA.:p. Since I haven't made that kind of adjustment since the old MG now I understand that it's not a wrenching thing on this motor.
 
The concept has not been well explained here. The theory with hydraulic lifters is to position the pushrod into the mid range of the plunger's travel so that it can compensate for wear and heat expansion.

Hydraulic lifters do not have a clearance. They have a pre-load value. Maximum plunger travel is about .180". The mid point obviously is .090". However, the OE calls for about .060" preload which tells us that they are calling for a little less than the midpoint.

How to measure preload is another thing and this is where your confusion lies. If you collapse the lifter entirely you can measure preload by referencing the bottomed out value and adding .120" to that. Or, take a dial indicator and simply torque everything down and measure the remaining amount of travel. This works great if you have new lifters and this is the method refered to in the manual.

If you have oil in the lifters then that method is not so easy. If the lifters are full of oil, then the easy way is to observe the point at which clearance reaches -0- and then carefully count the turns of the wrench from that point until the pedestal bolt draws tight. If that equals around 3/4 of one full turn then you are about right on .060" preload.

Typically if the cam and rocker arms are stock there is no reason to worry about preload but if either of those things have been changed then you should check pre-load.

The torque sequence has nothing to do with setting or observing pre-load. The torque values are only there to ensure that the bolt stays tight.
 
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