Which rocker arms?

So I busted a rocker Friday and I'm thinking now that one has failed others may be right behind it. I was using COMP Pro Magnum Steel full roller rockers... the one that failed busted what I guess you would call the steel trunion on the bottom that captivates the fulcrum roller...

Anyways I'm guessing the plain jane steel roller rockers just won't cut it... what should I use?

I'm running Lunati .630 mech roller cam with 250# on the seat and spin the motor up to (and maybe past) 7000 rpm.

Is there any weight penalty going to stainless or is extruded aluminum better... what are you guys running in your high revving big blocks?

Could this failure have occurred because I had the motor sitting for two months while I rewired the car and had too much pressure on the few valves that were open?

Thanks...

-Chris

i have used PBM / yellow terra .crane /lunati . scorpions/hoards. harland sharps. t@d . ss crowers i like them better then comps .i check them at mild lift so i know i get the right length push rods . all maker of rockers have dif geometry

Crowers have always been my favorites... Got 3 seasons on one set, still no problems.....

Thanks guys... good point on the geometry: Will I likely need to change push rods if I change out the rockers?

So stainless is best for durability? Are they not much heavier than aluminum?

Thanks for the suggestions... I'll do some more looking. Might not be something I get to this week but I'll feel better when I don't think another one is going to let loose.

Quote:

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Originally Posted by skids72

Thanks guys... good point on the geometry: Will I likely need to change push rods if I change out the rockers?

So stainless is best for durability? Are they not much heavier than aluminum?

Thanks for the suggestions... I'll do some more looking. Might not be something I get to this week but I'll feel better when I don't think another one is going to let loose.

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some do not like ss rockers a alum rocker dampens better less hamonics ? the crower not heavy whatever you do check your push rods this is a big deal you need to check it with your rocker arm you going to use not some blue plastic $5.00 thing

thanks again, Pat

so aluminum may be better cause the ringing don't come through the valve train too much(?)... I'm just thinking about what is not going to break... yunno you break something and replace it with something stronger and find out what will break next :whacked:

Sounds like swapping out rockers will be more than I should tackle for a race motor that needs to run hard soon... I was hoping it would be more straight forward but if I need to check/change push rod lengths I should leave it to the pros this time cuz I don't want to screw it up

I appreciate all the feedback...

-Chris

Quote:

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Originally Posted by skids72

thanks again, Pat

so aluminum may be better cause the ringing don't come through the valve train too much(?)... I'm just thinking about what is not going to break... yunno you break something and replace it with something stronger and find out what will break next :whacked:

Sounds like swapping out rockers will be more than I should tackle for a race motor that needs to run hard soon... I was hoping it would be more straight forward but if I need to check/change push rod lengths I should leave it to the pros this time cuz I don't want to screw it up

I appreciate all the feedback...

-Chris

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well you can check them with blueing on the valve stem roll over by hand should hit about middle of stem i do not do it this way but will work

roller tip should be a little on the outside of the center of stem fully closed and a little on the inside of center fully open, right?

I think I'll hold off on replacing them all for a while and just keep an eye out for any signs of cracking etc...

Thanks Pat and Dave for all the feedback...

-Chris

Opposite.....starts on the inside and travels outward or you'll wipe out the guides.

why are you running 250 on the seat of a 630 lift cam that you only want to turn 7000?

hey nitro... thanks for the clarification!

-Chris

Quote:

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Originally Posted by jerry clayton

why are you running 250 on the seat of a 630 lift cam that you only want to turn 7000?

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hi jerry,

why not? Is this overly excessive? Motor was built to hold together to 7500 but doesn't pull much beyond 6800 in it's present configuration (I think this is mainly limited by the 280cc oval heads)... what does it take to keep the roller lifters on the lobes at these revs? I was under the impression the springs were kinda tame compared to some of my similarly equipped counterparts...

thanks,

-Chris

With today's faster ramp rates on camshafts just about everyone is going to 225 to 250 for a seat pressure on a BBC at least for bracket type cars.

i run that much on the seat it works and push rod lay out is right photo is like MR Nitro shows allmost middle to out side but like i said i check at mild lift with a ferry geometry checker:3dSMILE:

Yep--and broken rockers, pulled studs, extruded keepers/retainers, bent pushrods, busted lifters----
Bracket racing???? come on --half the time they are on a throttle stop

I only ran around 200 seat pressure on 800 + lift that saw 9500= several times

if your valve train is light then you do not need as much spring and can go faster with less spring less chance of pushrod flex stud flex and every thing else flex. but when in doubt in run abit more spring in the sand drag engines i see things hit that never should

there is some things wrong i think with the big block heads as to how the rocker studs (stud rocker arms) are not at the same angle is the valve guilde you would think this would be the way you would want it ?? i have spent hours checking things at mid lift and working with the contact foot print i have a hard time with the rocker is on one side of the stem valve now it is over here now it should be right there ?? well

I'm just running the stock springs on these heads:

Trickflow PowerOval

Another guy running a 8.9xs Chevy II with the motor built out of the same shop is running .8xx lift in a ~650ci all aluminum big block that spins to 8000+ with 450# on his springs (but that's a whole different ball game :rolleyes: )

I know you know your stuff, Jerry, I'm just trying to reconcile the differences... I think most of the bracket racers (did I detect a tone of disdain there? :o ) with roller cams are up here in the same ball park with the springs. BTW I'm not on the throttle stop (and won't run in the classes that are) and still footbraking (to a 1.670 60' last time out :) hope I can get closer to 1.60 but we'll see).

I'm guilty of putting way too many street miles on what really is more of a race motor and I should expect to break stuff when I do that :HMMM:

Thanks,

-Chris

well i do not know one damn thing:D i run the isky 1.625 240 @2000and 685 @1.250 part #9685 i run them in both street cars for over six years but have SS valves and heavy roller lifters with no rev kit i do not think this is to much but it is alot. could less work? maybe but it works to 7500 rpm this i know:3dSMILE:

... forgot to mention I also am running a rev kit... apparently I don't need it but does it make a difference in all this?

-Chris

oh you will just wear out your roller lifters faster you may want to look at them sounds like yours could be on the way out

I like my throttle stop!!!! Best way I know of to keep the thing at 9.90!!!!

Quote:

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Originally Posted by jerry clayton

Yep--and broken rockers, pulled studs, extruded keepers/retainers, bent pushrods, busted lifters----
Bracket racing???? come on --half the time they are on a throttle stop

I only ran around 200 seat pressure on 800 + lift that saw 9500= several times

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I would like to know who made those springs and a part number.
In or USMTS engine that see's 8,200 lap after lap we run Isky Tool Room Gold Strip springs.
Part number 9935.Seat pressure is 245 lbs. and open pressure is 590 lbs.
We run a Jessel system and we have had no broken rockers,pulled studs,extruded keepers/retainers,bent pushrods,busted lifters etc.
In one race on a 1/2 mile track we have five hot laps,ten laps in the main,twenty laps in the feature.
In two nights of racing we will put on more time than an averge bracket racer does in half a season of bracket racing.
At around twenty nights we are putting in new springs.

No distain for bracket racers--just that those engines don't need as much to race---I think that most are buying way more engine than they need to run the brackets they do.

I ran probably one of the very first Jesel setups for BBC--rocker system and belt drive--Spring part numbers I don't remember but we used Isky's that Van Luven had stashed in the rafters when he worked there---

Did not use a rev kit!!!!

With racers running so much seat pressure---lots of them are getting into coil bind and this breaks parts big time---first a stud or rocker, then bend a valve, hang open and smack piston and then the biggie---all because of trying to run a high seat pressure with components that didn't match

I'm not saying this as slam toward anyone, but many times I've seen results of very sorry parts choices--and other times we get info on things like spring pressure, bearing and wall clearance, cc, etc that aren't even remotely close to actual engine specs and they wonder what went wrong.

Erik---I also have thousands of springs off late models and stock block Indy car engines---probably keep them because they cost so much I can't just throw them away--wish they were gold!!!!

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Originally Posted by jerry clayton

I also have thousands of springs off late models and stock block Indy car engines---probably keep them because they cost so much I can't just throw them away--wish they were gold!!!!

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yes i have some boxs of PSI springs to there getting recycle i using them in my streets engine if they check out there fine for me:3dSMILE:

Quote:

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Originally Posted by jerry clayton

No distain for bracket racers--just that those engines don't need as much to race---I think that most are buying way more engine than they need to run the brackets they do.

I ran probably one of the very first Jesel setups for BBC--rocker system and belt drive--Spring part numbers I don't remember but we used Isky's that Van Luven had stashed in the rafters when he worked there---

Did not use a rev kit!!!!

With racers running so much seat pressure---lots of them are getting into coil bind and this breaks parts big time---first a stud or rocker, then bend a valve, hang open and smack piston and then the biggie---all because of trying to run a high seat pressure with components that didn't match

I'm not saying this as slam toward anyone, but many times I've seen results of very sorry parts choices--and other times we get info on things like spring pressure, bearing and wall clearance, cc, etc that aren't even remotely close to actual engine specs and they wonder what went wrong.

Erik---I also have thousands of springs off late models and stock block Indy car engines---probably keep them because they cost so much I can't just throw them away--wish they were gold!!!!

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Jerry,you are preaching to the choir.
There is very little difference in a Late Model engine and a USMTS engine.
If racers are "getting into coil-bind" it is plain to me they have a spring that is to weak for their application.

Thanks everyone for your insights... I'll talk this all over with my engine builder and keep a close eye on everything in the meantime... double check lash every week and examine all the parts...

Here's a video of what happened:

http://videos.streetfire.net/video/F...ter_159857.htm

-Chris