Just rebuilt 258 now it's tapping help!

[djdelee421]

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?

[eaglefreek]

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

[djdelee421]

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.