Lifter preload discrepancy
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,185
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From: Virginia
Lifter preload discrepancy
Hey guys just wanted some input on this. I was measuring lifter preload today because I know I’m a little on the high side currently with my Johnson lifters and 7.425 pushrods. When measuring with an adjustable pushrod I’m coming up with about .065-.070 preload but when I do the rocker bolt turn method it takes slightly over 1 1/4 turns to hit 22ft lbs, which from what I understand should be around .100 of preload.
With the adjustable pushrod (and lifter on base circle of cam) I measured zero lash at 7.355 and with a 7.425 pushrod that should be right around .070. I was about to order a set of 7.4’s but now I’m confused
With the adjustable pushrod (and lifter on base circle of cam) I measured zero lash at 7.355 and with a 7.425 pushrod that should be right around .070. I was about to order a set of 7.4’s but now I’m confused
Last edited by bwill03z; Oct 12, 2023 at 12:04 PM.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,185
Likes: 265
From: Virginia
Right. This is exactly what I did…. Like I said with the cam on the base circle I got about 11.15 turns on my adjustable pushrod (approx 7.356 length) to reach zero lash. With that info and using a 7.425 pushrod I should be about .070 preload.
when I torque to 22ft lbs it’s 1 1/4 turns of the rocker bolt, and according to the chart that is nearly .100 preload… so what am I missing here?
edit: I just read step 6 that says AFTER 10ft lbs of torque you start counting the turns… maybe that’s where the difference is?
when I torque to 22ft lbs it’s 1 1/4 turns of the rocker bolt, and according to the chart that is nearly .100 preload… so what am I missing here?
edit: I just read step 6 that says AFTER 10ft lbs of torque you start counting the turns… maybe that’s where the difference is?
Last edited by bwill03z; Oct 12, 2023 at 02:35 PM.
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2021 C6 of the Year Finalist - Modified
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From: Erlanger, Kentucky
I go by the pushrod checker reading as it is a direct measurement and should be more accurate. I used the number of turns as a 2nd check just to verify the pushrod tool but it is much less precise.
And something to add, if you replace the rocker arm bolts with the ARP studs, the above preload checking method is invalid because the thread on the ARP studs that holds the rocker arm down is different.
I have the ARP studs so I have to use the pushrod checker.
And something to add, if you replace the rocker arm bolts with the ARP studs, the above preload checking method is invalid because the thread on the ARP studs that holds the rocker arm down is different.
I have the ARP studs so I have to use the pushrod checker.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,185
Likes: 265
From: Virginia
I go by the pushrod checker reading as it is a direct measurement and should be more accurate. I used the number of turns as a 2nd check just to verify the pushrod tool but it is much less precise.
And something to add, if you replace the rocker arm bolts with the ARP studs, the above preload checking method is invalid because the thread on the ARP studs that holds the rocker arm down is different.
I have the ARP studs so I have to use the pushrod checker.
And something to add, if you replace the rocker arm bolts with the ARP studs, the above preload checking method is invalid because the thread on the ARP studs that holds the rocker arm down is different.
I have the ARP studs so I have to use the pushrod checker.
For rocker bolts, whether I go with oem rockers or the shaft kit, would there be any difference in using the BTR trunnion kit bolts vs stock bolts? or are they about the same? If there’s no benefit I’ll just reuse the stock bolts
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From: Erlanger, Kentucky
Yeah I agree. I checked the intake on both cylinder 1 and 2 and came up with the same measurement using the adjustable pushrod so I’m going with that. I just bought a set of 7.4 pushrods so that should put me a lot closer to the correct preload for the Johnsons.
For rocker bolts, whether I go with oem rockers or the shaft kit, would there be any difference in using the BTR trunnion kit bolts vs stock bolts? or are they about the same? If there’s no benefit I’ll just reuse the stock bolts
For rocker bolts, whether I go with oem rockers or the shaft kit, would there be any difference in using the BTR trunnion kit bolts vs stock bolts? or are they about the same? If there’s no benefit I’ll just reuse the stock bolts
BTR bolts are likely a higher tensile strength bolt. But the GM bolts are excellent so I would re-use them. To me if I am going to upgrade bolts, I just go with ARP.