Like the title says - why adjustable rockers with a hydraulic cam?

This question came up recently with some car guys I know. I have used them before in a 340 - but really don't have a good answer.

I can answer that question! Dealing with that right now on my 383. In order to get reasonable preload, not only did I need custom pushrods, but they needed to be 2 different lengths. Since the pushrods tend to be within 0.005" tolerance of each other, I optimized the lengths and now have preload of 0.035" to 0.044" = right where I wanted to be.

Real pain and if I had adjustable rockers you just turn the adjuster screw instead of 2 different length pushrods.

Preload seems legit. I was thinking that people ditched stamped rockers because they weren't a true 1.5 ratio- but that's just a guess.0

I have heard this too.

I run adjustable roller rockers on all my toys, smblk and Bblk RB, I like the 1.6 ratio arms, usually Crane or Isky, plus I run anti pump up hyd. lifters on all the motors as well, so I need the adjustabilty factor, plus the 1.6 is good for up to another .050 lift on the cam with out getting the additional duration

mainly for preload #2 wipe pattern 3rd is pushrod angle at adjuster cup

Does the preload become more important with a larger, more aggressive cam? Just curious why most stock engines had non adjustable rockers.

Also if you run a decked block and or milled heads it changes the lifter preload so they are nice to have to set preload as was said. Ron

Are ductile iron adjustable rockers ok for a 500 horse street 440?

Yes, iron rockers are good for a decent sized cam. Iron rockers were about all you could get for a long time. Ran a bunch of 557 and 590 mechanicals using iron rockers.

OEM they weren't used because stamped rockers are a bunch cheaper to produce/buy than iron pieces.

Stamped rockers don't always hold up well to stiffer springs and more rpm too.

I ran them on my 383 with no preload, zero lash. It would turn 68-7000 with no pump up. I was skeptical when told this, but it worked. Told to do the same with the stocker 340 engine that turns 75-8000 in the as yet unfinished race car. Those lifters only have 0.015 of compression though.

you really need adjustable rockers for any cam that's higher than stock lift. with stock rocker arms, the higher the lift of the cam, the deeper you sinking the pushrod into the lifter. go high enough with with the cam and you'll bottom out the lifter. adjustable rockers will allow you to compensate for this problem.

the very first 440 i ever built was with a .509 purple cam and stock rockers. I didn't know any better at the time. within 100 miles, wound up wiping the cam and all the metal destroyed the engine. costly lesson.

Plus custom push rods to keep it all happy.

The last 2 hyd. cam builds I did I went with adjustable pushrods, I got the exact amount of preload I wanted on every lifter.