Sand washers for head studs

[37 truck]

I bought an ARP head stud kit for my flathead, and read somewhere that you should sand the washers prior to installation. Anyone have insight on this? The washers seem to have a cross hatch from the manufacturer.

[19Fordy]

Sanding doesn't make any sense as the X- hatching will hinder spinning. QWhy would they sell washers you need to sand?

[deuce_roadster]

I can think of no good reason you would sand washers unless you wanted them thinner.

[JSeery]

I've read this somewhere, I believe it is ARPs advice.

[Ronnie]

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[Frank Miller]

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This is my guess. During mass production a washer can have a burr on the edge. It won't make a difference in most cases but is you take a washer and run it over sandpaper on a flat surface - drill press table will work fine - you will ensure there is no burr digging into the head. High spots will readily show up and you will probably not remove more than a couple of thousandths.

[JSeery]

Found some information on this. It appears that if the washer and the spot face surface on the head are too smooth it allows the washer to spin while being torqued. This over torques the stud. ARP was recommending sanding the washer surface to reduce the chance of the washer spinning.

"Their recommendation is to push the cylinder head side of the washer down the length of a 12-inch length of 60-grit sandpaper three times. This will create a rough finish that will prevent the washer from spinning as torque is applied."

"On ARP head stud kits there is no radius because it’s not necessary. In this case, it doesn’t matter which side of the washer is sanded, as long as the rough side is placed facing the cylinder head."

"This odd situation has occurred because a combination of the smoother finish on the head bolt washer has combined with the smoother spot face finish on many new cylinder heads. The good news is that the fix for this is very easy and costs nothing. ARP’s simple fix is to just roughen the finish on one side of the head bolt washer with 60-grit sandpaper and the problem is solved. That means you should create the rough surface on the cylinder head side of the washer to prevent it from spinning."

There is a long explanation as to why this is an issue, but the short answer is you don't want the washer spinning on the head surface while torqueing head bolts or studs. If the washer is turning it acts similar to a bearing and interferes with getting the correct clamping forces. Basically you end up with an over-torqued situation which has lead to stud/bolt/thread damage.

This information was from the LSX magazine site, and NOT directly from ARP.