http://www.cranecams.com/master/radiarc.htm

Any longevity durability problesm with them? Woud a steel rocker such as a promag keep valvelash better than an aluminum body? They say for 1.50 diamter sprigns, could they be ground to fit 943s or no? ANy experience with these rockers?

 

With the high lift rates (high "cam velocity") possible with solid rollers, the stiffness of the rocker arm, or it's resistance to bending when loaded, is the most important attribute.

I believe the Comp Pro Mag is stiffer than most/all aluminum rockers.

The variable ratio feature just means you can change pushrod seats to more or less offset. Anytime there are removable pieces, the overall stiffness may suffer.

Anytime you remove material from a rocker arm, you are probably compromising stiffness.

My $.02

 

Do they make a 1.7 ratio promag?

 

Not for the Small Block.

There is a High-Tech Stainless 1.7 for SBC. P/N 1117.

http://www.compcams.com/catalog/

 

Crower makes ratios everywhere from 1.5-1.9:1 in stud-mount sbc rockers. #73643 is a standard type rocker that'll clear springs up to 1.56" in diameter... the #73673 is their long-arm/backset rocker and it'll clear spring diameters up to 1.65. Made very similiar to the Pro Mags, just in 17-4PH stainless and a little steeper in price. Very nice rockers though.

-Mindgame

 

I'm running the Crane variable ratios on my car, granated I'm still running a stock cam. I do not see any problem with these rockers working well with a mild solid roller. Also these rockers a not roller tip which makes setting lash a bit easier & more accurate in my book. I really do not know what the limitation is for these rockers as far as handling VERY high spring pressures.
I do plan on using a set in my next motor which will be a solid roller in the .630 lift range.
Steve...

 

Why do you think it makes settng lash easier, or more accurate? Somethin I should consder possibly.

 

Well in the past I've had an easier time setting the lash on various types of engines equipped with solid lifters (roller & flat) when the rockers are not roller tipped. With a roller tip you really need to slide the feeler gauge horizontal in relation to the roller so that you are not "rolling" the tip. It's easy to have the lash a hair too tight and the roller move and make things feel looer that they really are. It's just some thing I noticed years back when I set two solid cams in one afternoon. Granted the engines were very different, but the principals were identical. The first engine was a solid roller 327 in a 280Z. The owner had installed a set of Comp Cams 1.52 RR's (this was when they first came out) and asked me to run through the valves for him. I wound up running through it twice since the 1st time I slid the gauge with the rollers. Going back through a 2nd time to check myself I slid the gauge in a front to rear motion in relation to the engine and noticed a tighter feel. I don't recall the difference I found between the two passes, but I did loosen it up a bit on the 2nd pass. The second engine that day was a 903ci V8 turbo marine diesel. Solid roller, 4 valve per cylinder with a 3rd lobe per cylinder for mechanical fuel injection. The cam/valvetrain setup on this engine is almost identical to a chevy in geometry... push rods actuating rocker arms. On this setup the two int/exh valves were connected per type with a bridge that the rocker arm pushed down (one rocker operates two valves). The rocker arms were roller fulcrum, but radius tipped. On this arrangement the feeler gauge could be moved in any direction and still have the same feel, I found that I could run through the settings easier since I was dealing with two "fixed" surfaces and would get consistent resistance in all directions when checking clearance. I hope this helps to illustrate my reasoning... clear as mud??? lol
Steve...