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New Lifter Preload Question

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Old 08-13-2011, 11:08 AM
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daningraham daningraham is offline
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New Lifter Preload Question

I purchased a new "rebuilt" 390 and broke it apart to see what had been done to it and found that it only had a stock cam and spring set in it. I purchased a new Comp 268H cam and lifter set and reinstalled it, along with the brand new pushrods that came with it and according the the directions from Comp the "preload" setting is measured by installing the pushrods/rockers and tightening them down at TDC and then measuring the travel of the pushrod as I untorque the rocker shaft bolt till the travel stops. Their spec calls for this to be between .045 and .060.

I did this procedure using a caliper, resting it on the head gasket flange and setting it to zero and then reading the gap as I unbolted the rocker. Using the new 9.62 pushrods that came with the motor, I came up with .123. If this is the correct procedure, I am going to need to find a set of pushrods that are in the 9.55 range, which appears to be an atypical size for a Ford application.

The Ford manual I have calls out a "collapsed lifter gap" for this motor to be between .119 and .169, is this the same thing as "lifter preload".

This is the first top end work that I have done and really don't want to screw something up from the beginning. Thanks in advance for any info on this.

Am I doing this procedure correct?
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Old 08-14-2011, 07:57 AM
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Sleepy445FE Sleepy445FE is offline
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Quote:
Originally Posted by daningraham View Post
I purchased a new "rebuilt" 390 and broke it apart to see what had been done to it and found that it only had a stock cam and spring set in it. I purchased a new Comp 268H cam and lifter set and reinstalled it, along with the brand new pushrods that came with it and according the the directions from Comp the "preload" setting is measured by installing the pushrods/rockers and tightening them down at TDC and then measuring the travel of the pushrod as I untorque the rocker shaft bolt till the travel stops. Their spec calls for this to be between .045 and .060.

I did this procedure using a caliper, resting it on the head gasket flange and setting it to zero and then reading the gap as I unbolted the rocker. Using the new 9.62 pushrods that came with the motor, I came up with .123. If this is the correct procedure, I am going to need to find a set of pushrods that are in the 9.55 range, which appears to be an atypical size for a Ford application.

The Ford manual I have calls out a "collapsed lifter gap" for this motor to be between .119 and .169, is this the same thing as "lifter preload".

This is the first top end work that I have done and really don't want to screw something up from the beginning. Thanks in advance for any info on this.

Am I doing this procedure correct?

Check out the links in this thread. https://www.ford-trucks.com/forums/1...binations.html

That's the way the Ford manual says to check it. With unused lifters it won't be a pain to bleed them down either. You can get quality custom sized pushrods from Smith Bros. if you have to. The stock ones come in .060 increments.
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Old 09-04-2011, 01:13 AM
neon tony neon tony is offline
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get a set of adjustable pushrods. with the cam on the base circle, adjust to zero lash, preload 1/2 turn and measure the pushrod. go with the closest factory length. my stock ones are 9.59. iirc there's a shorter one.
for measuring, 12" digital caliper from harbor freight. only $50.
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Old 09-04-2011, 02:46 PM
85e150six4mtod 85e150six4mtod is offline
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Valve springs. Did you upgrade valve springs? Your springs must play with your cam. Stock springs might coil bind or cause valve float if that cam and your set up runs much over 4500 rpm.
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