I can't imagine seeing a huge difference after changing just the rockers and lifters any way.In my experience if you're gonna change one part of the valve train you'd be better off changing it all(cam,lifters,valves,push rods etc...) maybe I'm stupid I dunno.I had a buddy who tried swapping out his cam for a bigger one and after a month of breaking stuff he gave up.He was goung on the advice of many high performance parts dealers.They just wanns sell you crap.

 

Just to add to the muddyness of this subject, Fulcrum height could be an issue if it's not some sticky liftershelping make variable pre load heights! As the first set of Hughes 1.7 arm's I used on a stock 5.9 with 6.905 push rod length had some of thepre loads variying upon reassembly Iused like one shim per arm out of the two thickness shims supplied after Idisassembled and cleand upthe lifters (several were stuck internaly) andpre loadwas around .050 without removing the heads for any other work.

Second set of Hughes 1.7's came with no shims in the box! and using R/T head P5007141 I ended up using sb Ford push rods 6.804 and the extra shims from the first setto get .040 preload, these head's had .008lb and .014rb taken off and .004 off the deck's (10.8cr).

Third set of Hughes 1.7's on yet another engine came with like 70 shims!! and used the P5007141 heads with .010off both heads, wanted no shims to get a .030 preload using 6.905 push rod length.
Go figure.

Fourth 5.9 with stock not cracked heads! with .020 off them and .008 off the decks Iused 73643 1.7 Crower arms and made it work with a 7/16 stud conversion and again sb Ford pushrods.

Number 5, 5.9 using stock heads with .007lb and .011rb off and .008ld and .010rd off the decks, The client brought Sharps that needed .045 shimming to use stock length 6.905 pushrod but worked fine other wise.

And then I used the 73643 1.7Crower ss arms on myV-10 doing the7/16 stud conversionto use the Chevy arms (+1.97 intakes same time) and used Smith brothers adjustable push rods to get the pre load length of which I didn't record! I drive it daily and if I ever take it apart may measure them!

By the way the 7/16 conversion stud I used isa3/8-16 lower and have7/16-20 top thread.

Just some useless additional info, best thing is to measure things for yerself!, Then you know.

Crower does spec out 5500 rpm V-10 and 6300 rpm Viper part numbers.More mudd for the muddiness!

 

So I guess Cummins is no longer trying to sell these rockers?

 

10-4on fulcrum height. I think problems with this occur when people use the incorrect rockers and try to compensate with pushrod length. You can get them set up right when the valve is closed, but then they are way off when the valve is open. Been there, done that. I know it sounds ****, but , from a piece of mind standpoint,IMO it's best just to get the rightadj. rockers with the right pushrods than to mess around withshims. Though, ifyour customer brings you something, I guess you are obliged to use it.


LomcevakDuck,
If you haven't already, I would try emailing the cummins guy. He only had 7 posts when he started this thread. I doubt he is on here much. Click on his user name, and then click email instead of pm.