[Cliff R]

Use the hydraulic lifters that you are going to run when measuring for pushrod length, or you will have to take one of them apart (not recommended) and shim it up to where you are going to run it to make the measurements.

What we do here is to set the pre-load where we are going to run them, then bottom out the lifters and measure the additional travel. With the lifters bottomed out, mark the valve tip and adjust the pushrod (adjustable) until you determine the ideal pushrod length. Then subtract the additional travel from your measurement, and you have the correct pushrod length.

Look for the narrowest pattern as close to being centered on the valve tip as possible. This may take some time, but it is worth the effort.

For example, the 455 we just finished use HR lifters that had a total of .140" travel. this was apprx 1.5 turns with the locknuts. We set the pre-load at .070", or about 3/4 turns down from zero lash. We bottomed out the plunger then did the measurements, then subtracted .070" from the result.

The pushrod lengths required on these engines are all over the map these days, due to the different items used with the valvetrain, and decking/squaring blocks and milling heads. Just going from one brand of rocker to the next will typically come up with a different length.

Other items in the mix change the length required as well. Cam base circle, brand/type of lifter, type of head, valve length used in them, and brand/type of rocker arm.

The shortest we've used to date have been 8.900", and have needed clear up to 9.850's for a few engines.

I would also recommend going to heavier wall pushrods if you find yourself buying a custom set, unless it is a near stone stock set-up with stock spring loads/small cam, and will never see much past 5000rpms.

Although we've never had any failures with .080" wall pushrods, they few engines we've been back into that used them had "witness" marks on the pushrods where they were flexing around quite a bit and rubbing where they go up thru the heads. This problem does not happen with the thicker wall pushrods, as we've been checking several engines used for street/strip action that we built here in the past few years, including my own.

Another problem we run into as it relates to this topic, is not enough engagement with the locknuts. I will not assemble one of these engines and put it in service with at least 5 full turns with the locknuts. We've had to get longer studs or shim up the ones supplied with the heads on occassion. The length of the locknuts also has them hitting most stock covers, so we find ourselves using thicker gaskets, or getting shorter locknuts or machining down the set supplied in the lathe for the needed clearance......Cliff