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  • March 28, 2024, 11:45:18 AM

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Author Topic: Just rebuilt 258 now it's tapping help!  (Read 7208 times)

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Offline djdelee421

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Re: Just rebuilt 258 now it's tapping help!
« Reply #30 on: September 26, 2018, 09:19:34 PM »
How do I check preload? I just thought you torque it to spec and your done. Are you saying that I could have a couple pushrods the wrong size and some are okay?
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Offline eaglefreek

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Re: Just rebuilt 258 now it's tapping help!
« Reply #31 on: September 27, 2018, 10:03:59 PM »
hi, technically there is NO lifter preload spec. You have hydraulic lifters, so if your lifters/pushrods/rockers are factory, all should be well. A couple of thousands shave to straighten head should not alter anything. good luck, gz

Lifter preload is a thing and needs to be checked especially when  an engine is rebuilt and/or parts are mixed from different engines and machine work has been done. I replaced a cam in my dad's Oldsmobile about a year ago and since it doesn't have adjustable rockers just lie the 258, I had to check lifter preload to make sure I got the right pushrods. I bought a lifter and disassembled it and reoved the spring.. I then found some washers that fit in the lifter that gave me the desired preload figure. I think I shot for .040. Here's an article explaining lifter preload
http://www.laneautomotive.com/PumpItUp.htm
1986 AMC Eagle Wagon 4.2L/4.0L head, AW4,NP242, Chrysler 8.25" rear.
1981 AMC Eagle Wagon As Seen On TV  Lost In Transmission


 

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Offline djdelee421

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Re: Just rebuilt 258 now it's tapping help!
« Reply #32 on: September 27, 2018, 10:47:05 PM »
Wow after reading that I'm thinking that I need longer pushrods and not shorter. Somewhere I read to check the pre load you make a mark on a pushrod at tdc and then loosen the rocker all the way make another mark and between them is the pre load. Am I correct.
83 sx4 driver
83 wagon limited (project)
85 wagon limited (parts)
86 wagon driver
73 VW beetle (project)
68 Kaiser jeep (project)
85 GMC Sierra (project)
98 24valve Cummins work truck (beast)
94 suburban daily driver
93 freightliner FLD 120 (beast)

 

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