Pushrod length and what would cause longer or shorter ones

[sext7366]

My machine shop guy said he was still working with the heads because whoever rebuilt them last had installed retainers which were offset
Hmmmm I have no idea what this means but he went on to say that it may cause me to need longer or shorter pushrods which could not be determined until the heads were put back on the motor. I am purely guessing but is this because of a different degree retainer? from what I can tell the stock retainers were 7 degrees? and my last cam was a comp cam who offers a 10 degree retainer.  So in essence if my pushrods were also changed it is all ok, but id they are the stock pushrods they may be off?

If I am way off on this let me know he was very brief in describing this to me on the phone because I was at work.  If so what else could cause the pushrods to be off, and how can I check once I get the motor and heads back?

[firefighter3931]

When the heads are rebuilt, valvestem heights need to be uniform. You can check this by placing a straitedge across the tips to see if there is uniformity. Sometimes with old heads the valves will sink into the seats and create an issue where the stem heights vary....this needs to be corrected. The retainer/locks whether it's 7* or 10* won't affect the installed height.

Head milling, block decking and head gasket thickness will influence valvetrain geometry and ultimately pushrod length. There is a fair amount of play with a hydraulic lifter where .020 preload is ideal but up to .060 is acceptable. Solid cams are not as forgiving and everythng needs to be bang on.

Ron