Rocker Arm Adjustment

[Janusz]

I recently removed my valve covers and found a chipped Crane roller rocker arm. I believe it was due to a clearance problem with the valve cover (came that way). Ordered a new arm and replaced the damaged unit and readjusted the remaining rocker arms following the Comp Cams manual:

Turn the engine until the exhaust pushrod just begins to move upward to open the exhaust valve. Adjust the intake rocker by spinning the pushrod until you feel resistance and then turn the adjusting nut 1/2 more turn.

Turn the engine until the intake pushrod comes all the way up and almost all the way down. Adjust the exhaust rocker the same way including the additional 1/2 turn.

The engine started easy and ran smooth before ....... now it struggles and stumbles, wanting to shut down. I found most of the pushrods spun freely in the above adjusting position prior to making any of the adjustments, so now I'm wondering if the preload is set too high, and if so, is there a better way of measuring it.

Engine is a 351W Sportsman block, with SVO aluminum "High-Flow" heads. Rocker arms are Crane adjustable arms and cam is a Comp Cam 35-430-8. Cam spec's are:

Valve lift .560 int / .560 exh
Tappet lift 280 int / 280 exh
Valve timing 34 BTDC open int / 66 ABDC close int
74 BBDC open exh / 26 ATDC close exh

Looking for any suggestions.

John