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Aftermarket heads. RHS Pro Torkers. 350 SBC. hydr. flat tappet @.500 lift cam. roller rockers. 7/16 studs. My valves are +.100 longer than stock. WIth a solid lifter a +.100 longer pushrod put the pattern right in the middle of the stem. With a hydr lifter a stock lenght 7.80 put the pattern right in the middle of the stem and with the +100 it was way to the outside. My plastic length checker puts it at about +.050. I would think the stock length 7.80 would be correct? It shouldn't be this difficult.
 

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Typically, SBC lifters....solid flat tappet has a lower seat height for the pushrod cup than the hydraulic lifters do. It's just how they are made.

Use the video posted previously ^^^^ to determine correct pushrod length.
 

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You would have to start with the need to use a .1 inch longer pushrod. The reason is the entire spring pad and rocker stud are moved up .1 inch. This is the result of using thicker walls than the OEM to gain strength while still allowing suitably sized coolant passages. This drives a longer stem valve and requires a longer length push rod.

Now if your deviating from the ranges of factory cams in lift and or duration especially if going to aftermarket roller lifters then you need to use an adjustable push rod with a lighter pressure check spring in an engine mock-up assembly to check for actual sweep on the stem. The sweep pattern will then determine the actual pushrod length when using stud mounted rockers. If you convert to shaft rockers the details are a little different as these use shims under the shaft mounts and the rockers have a threaded adjuster that either sets preload on hydraulic lifters or sets lash for solid tappets. If you’re using aftermarket retro rollers you have to go through this process as not all aftermarket cam assemblies fall on factory push rod dimensions.

Bogie
 
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