Standard Deck Height?

[MtyMous]

Hey guys. Looking to see if anyone knows the standard distance between the top of the piston and the block deck also know as "piston deck height".

I'm trying to take some measurements and set my rocker lash but I need to put spacers under the rockers to accommodate the amount of material that was removed when my block was zero decked. Unfortunately, my machinist didn't measure that before he decked it. soooo. I'm looking for the standard measurement.

Anyone know what it is?

[jeff10049]

It varied a lot depending on piston pin height in different years but a .020 shim should suffice. He may have taken off as much as .033 from the block.
If the head was milled too maybe a .030-.040 shim really the adjusting screw should be enough to handle it is it not? If not did the base circle diameter of the cam change?  Normally the adjusting screw can be backed off to over .125 of clearance I doubt that much was removed something big seems to have changed.

[MtyMous]

Thanks jeff. The block was zero decked. The head was skimmed. But it's a custom build from specialist components so I'm not sure exactly how much.

With the high lift of the 286 cam, the MED 1.5 LDX rockers, and the deck height adjustment, id like to get the intended pushrod and lifter geometry close to design spec without having to crank the adjuster screw to the limit and create an unintended stress point.

You're right. I probably could, but i already have shims. Lol

Thanks for the info though!

[MiniDave]

You can pretty much eyeball this, you want the rocker to contact as close as possible to the center of the valve  and you don't want the rocker to be off the tip either direction (front or back edge of the contact tip on the rocker) if they only took that much off it should be fine with std rocker geometry. They're going to be off to the sides somewhat due to the location of the posts, but you can shim for this too. I used the solid shim kit MiniSpares offers but in the future I'd probably just use the usual springs and shim the rocker over as needed and as much as possible. You want the rocker slightly offset so it will rotate the valve a little each time it contacts it.

Like Jeff says, the piston pin height/piston top height will determine how much it's safe to take off the block, in the engine I built for Dan I left .005 clearance for future needs.

[jeff10049]

Shimming the rocker pedestal may not be the way to go but rather a shorter pushrod to keep the geometry right. 

As Dave Said the rocker should stay close to center on the stem normally it starts slightly to one side of center and ends at full lift slightly on the other side of center. some engines cross center and end up back in the same spot at full lift the important thing is that you are never on the edge of the stem or worse yet run off the stem and hit the retainer.

Shimming the rockers would be more to correct valve installed height, not the deck/head milling or cam base circle that is normally done with pushrods.

You do have different rockers though so you may need to shim anyway I have also had to remove material from the rocker pedestal. who knows what the installed height is on the valves at this point.