Re: Roller rockers
 

My AMX in D/S had 450#'s open pressure when it was running 10.50's. And I know some guys (multi-makes) running around 480#'s nowadays.
I shifted mine at 6800 RPM, not something I would call "extreme", went through the traps about the same.
Broke rockers all the time. Coated them, cryo'd them, ARP 7/16" studs (AMC is like a SBC rocker assembly) best fix was adjust valves every two to three runs. Guide plates & unlimited style valve spring were not legal at the time.
If I were doing it again I would try 7/16" dual taper pushrods with guide plates & a double (triple?) spring.

Some would say the cam profile was wrong. I don't know, had about a half-dozen in the car over the years, all custom grinds. Didn't break rockers too often until the spring pressures got up to 420. But then again the car got faster with the cam and springs.

Now when you look at it, NHRA will allow $1000 billet or tool steel cam cores, $800 Schubeck lifters (that may take out your engine) or tool steel lifters, they'll allow $600 push rods, they will allow beehive or ANY valve spring you want (neither allowed when I ran Stock) that can approach $500 a set, stainless valves, $750+ BBC 8.2L rockers with the whammy treatment and 1/2" rocker studs....but it would be ridiculous to allow $279 Crane Gold roller rockers that would live with the rest of the valve train! :rolleyes:

Re: Roller rockers
 

But Jeff their not "stock" (unless you have an LT4 vette) besides we get enough sticker money why would we want to get it for rocker rams?

Re: Roller rockers
 

Even with the milder RPM's you ran at I suspect the "square lobe" cam I assume you started running and the increased spring pressure required to make the lifter follow the lobe was a cause of the breakage. Stock just "Ain't" stock anymore. Its wilder than the early early early Modified Production engines. I know they are more modified and wilder than my SS/IA 68 Camaro engine was in 1977-78 !

Re: Roller rockers
 

In regards to the solid lifters being an issue: How is it that bracket racers are running near .680 -.700 lift mechanical cams and not breaking lifters???

The factory rocker arms with the higher spring pressures I understand, but the lifters I don't.

A very good friend of mine was running a custom (BBC) high lift mechanical/solid cam from Crower and never had any issues with his$100 set of lifters breaking. He would easily get 400 passes on them shifting in the mid 7k range.

Re: Roller rockers
 

nothing to do with lift, all has to do with ramp rate. if you have 260@.050 duration on a .750 lift cam that is one thing, now if you have .300 less lift your ramp rate is increased dramatically with the same duration

Re: Roller rockers
 

That's why anybody can build a fast bracket racing type engine.
Likewise, my 3160+ weight stocker with .457" maximum lift cam and a little 600 CFM Autolite carb can beat most Dominator equipped .700" lift engines which weigh 300 #'s less. Of course that's part of the fun...

Re: Roller rockers
 

One of my favorite things to discuss is cryogenic processing. I love when someone tells me I tried that a couple years ago and it didn't work. Well, a couple years ago you ran your computer with dos.....cryogenic processing ain't what it use to be! Additionally, all cryo is not the same! There are new machines,(very important), new programing available, and unlimited control over the process. Some new machines never directly expose the parts to the liquid nitrogen. It even has cause some manufactures to say their parts are already cryo'd. OK, but was it done correctly? Ask what machine was used, old it is, and how long did the process take. Ask questions. ( you can't cryo a part, correctly, in less than 3 days -72 hours-).We've developed programs that have eliminated roller lifter breakage in Pro Stock, eliminated valve spring breakage, eliminated timing chain stretch, and done a very good job with rear end gears and stock stamped steel rockers, among other parts that fail. I will tell you that dry ice in a bucket isn't used, and that all parts are treated with different programs, and, I can make your high speed drill bits last 10 times longer - guaranteed. JB.

Re: Roller rockers
 

All very good points Jim!

Re: Roller rockers
 

Mr. Bailey, i think is right on target with cryogenics done properly it works very well. ive also used the metaltt lax process . what i like about metal lax is before you treat the part it gives you a graph showing how tight the grain structure is before you start, then what it is after a cycle. i know on titanium it machines better and holds up longer. for example, titanium rods in a sprint car used to change , every 2 weeks. after metal lax , 6 weeks without breaking one. anyone else on this?