Adjustable rockers necessary??

Lil Demon said

Hi, I am getting ready to build up my 340 with X heads. I will be using the XE268 from Comp. My machinist insists that I use adjustable rockers. After shopping around I don't really feel like dropping that kind of cash for them. Are they really necessary? Or will a new Mopar rocker set be sufficient? I imagine he is concerned with uniformity in lifter preload. Can that be obtained with non-adjustable rockers? Any advise would be appreciated.

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Absolutely go with a set of 273 Adjustable Rockers.

The deflection in the stamped steel units can be up to .005"
under a high-load rate.

In normal driving, you won't be able to tell the difference, but
in upper RPM's there is a noticeable HP edge, as there is less friction as well.

The Comp Cams XE268 has a .477" Lift and 268*/280* Duration, so clearance
between the Valve Spring Retainer and under-side of the Rocker Arm should be
adequate.

If you're going with the Com Cam #901 Valve Springs {101 lbs. @ 1.625" and 242 lbs. @ 1.250"}
there again should be adequate clearance.