How often is it necessary to mill rocker stands to accommodate high-lift cams? My net valve lift will be .485. 

It is not patently necessary.  Milling (or shimming) is used to correct geometry, which has many benefits but it is not a necessity for most cases.  There may be extremes where it becomes necessary.  I'll let others who may know expand on that.

Assuming that geometry starts in an ideal configuration, any subsequent change to the valvetrain will require an adjustment be made, whether that is milling stands or shimming stands in order to return it to an ideal configuration.  Items that affect geometry are pushrod length, rocker ratio, rocker tip style, cam lift, valve stem length, depth of valve at the seat, lash caps (not common), probably others I'm forgetting.

If using roller rockers, I think you will most likely need to shim the stands.  It may be possible that with factory style rockers milling is required.  You do need to check before you do either.  Exactly how much adjustment is required is something that has to be determined on a case-by-case basis.

The bottom line is if you want the geometry to be correct, shimming or milling will be required.



Lawrenceville, GA

Several things needed to be addressed before moving the rocker stands.  Was the block decked?  How much?  Were the heads milled?  How much?  New camshaft?  New lifters? New pushrods?  New rocker arms, or different rocker arm ratio? Valves replaced?  Stock or longer valves?  Valve job completed after all machine work on block and heads?  Typically milling the heads, decking the block and new longer stem valves will require adding shims, not milling the stands.  I had to add a 3/16" steel shim on my iron heads after all the above work was accomplished to get the rocker arm centered on the valve stem tip at mid lift.  Joe-JDC

JDC

Thanks, Joe. In my case, it's theoretical until the engine is assembled with rocker assemblies installed. After reading Ted's article, I thought that more valve lift would require milling the stands, not adding shims. Are the shims readily available? I will hold off on pressurizing the rocker arms until I know for certain. 

A lot of factors affect geometry, with lift being one of them.

For mine, I needed a shim just under 1/4" thick.  I'm not aware of any readily available shims.  I did use arbor shims to help determine the thickness needed but made shims out of a piece of 1/4" thick aluminum strip, 3/4" wide.



Lawrenceville, GA

The early OEM Y-Block stand oil trays I have are around .043”, if that’s any help.  If your target measurement is in the ballpark, finding a used set would likely simplify things (?).

6 VOLTS/POS. GRD. NW INDIANA

I have the oil tray baffles from my 55 heads. I will determine rocker arm geometry on 57 G heads with & without baffles to see which is better. Thanks, Daniel.

if you are using new style head gaskets(like I did) I did not use the metal spacers that wher suppose to direct oil.when I measured  new style head gaskets the increased thickness and the thickness of the plates ,returned the rocker geometry  back to stock
I would recommend 302 valve seales,but trim them so they are a bit shorter ,not as short as corect seals for y blocks
 I have found supper lube going to all valve train as well as plenty of drainage back to pan both ends.
my own truck with 292 y never had to change rockers to valve stem adjustment as whole valve train gets proper lubrecation

have only rebuilt 4ys the last4 years but no complaints from any  one

I would expect those changes to require pushrod length be altered but not require any significant change to stand positioning.  Since the Y uses shaft mounted rockers, the relation of the rocker to the valve stays the same no matter how much is removed from deck surfaces.




Lawrenceville, GA

have you  measured the latest head gaskets,in my case the thicker gaskets wher the same thickness as the trays.so with trays removed should be a time to check other changes (re surfacing heads and block).
also be careful with the head cap screws. the picture of ones being used(in 1 picture spells trouble