Posted By: '72CudaRacer
RB rocker arms w/ roller cams - 06/01/14 08:42 PM
I have another racers engine in my shop for repair. It has a broke rocker arm, but I feel like the rockers are not of a high enough quality to run with the spring pressures of a roller cam.
We don't know ANY specs on this engine(do not know who built it or what brand parts were used in it) other than what has brand names & part #'s on them or what we can measure.
It is a 500 ci RB(stock block), it has Brodix B1-BS heads with a LOT of hand port work, a mechanical roller cam with .690 lift (w/ 1.5 rockers).
The rockers appear to be PRW's maybe. We are going to replace them with either Harland Sharps or Hughes. Does anyone on here have any real world experiance with Hughes rockers?
Also, I think this engine has way too much cam lift. Any sugustions on this?
Thanks,
Brian
Posted By: Thumperdart
Re: RB rocker arms w/ roller cams - 06/01/14 08:53 PM
Been runnin the rollerized HS`s for years and love em but understand the new bushed ones are prefered by some. No clue on the Hughes though........
Posted By: AndyF
Re: RB rocker arms w/ roller cams - 06/02/14 02:31 AM
.690 lift with 1.5 rocker arms is a .460 lobe lift which is a fairly aggressive race cam. I run a .452 lobe roller cam in my 514 with a 1.85 rocker arm and I've never had any trouble with rocker arms but I use the Jesel setup. A .460 lobe will kill el-cheapo rocker arms fairly quickly, especially if the engine sees much RPM. My guess is with 500 cubes and B1-BS heads the engine is shifted at 6200-6500 so the valvetrain should last.
That engine might need better pushrods. A lot of valvetrain issues are caused by wimpy pushrods. I use 1/2 inch pushrods on the intake and 7/16 on the exhaust. If that motors has 3/8 pushrods in it then I'd start there.
Posted By: Thumperdart
Re: RB rocker arms w/ roller cams - 06/02/14 05:38 PM
Andy, my roller is .680-.660 w/240 seat and 580+ open iirc and I run 3/8 p/rods and they are holding up fine. I was concerned because they`re only .065 wall but Smith Bros. said that`s what they recommended..............
Posted By: FastmOp
Re: RB rocker arms w/ roller cams - 06/02/14 08:17 PM
I also run more lift and spring but with cheep Indy black rockers. The rockers can break if the guy lashing gets to agressive on the lock nuts.
If you stick a smaller cam in it make sure you tell him it's going to slow down.
Posted By: 440lebaron
Re: RB rocker arms w/ roller cams - 06/02/14 08:35 PM
I think anything under .650 lift would be a waste of B1 heads
gary
Posted By: 68Bullet
Re: RB rocker arms w/ roller cams - 06/03/14 10:22 PM
I can tell you from experience that I would be hesitant to run any aluminum rocker on a high RPM engine with high lift cam or spring over say 500 lbs open. I ran a set of Dove roller rockers (sold by Hughes in 2004 until they changed to an in house design) on my 383 with COMP street mechanical roller cam. I broke 2 rockers before I wizened up and bought the COMP magnum rockers, made of steel. Aluminum will stress fatigue and eventually break given a high enough number of cycles. Steel on the other hand, potentially will last an infinite number of cycles if the stress is low enough.
I cannot tell you where the cutoff would be where aluminum is guaranteed to break. My aluminum rockers lasted 10k miles of street driving with 500 pound open pressure springs at only .550 lift. Some may say that is a decent lifespan for aluminum rockers. But once one broke (and I thought it was an isolated incident), the second broke only 60 miles later. The hassle, cost and downtime of all of the repair work makes me wish I'd ponied up for the COMP rockers up front.
Bottom line is to discuss your application and get a guarantee from the seller. Otherwise you should always err on the side of caution and pony up for better components. Granted to I did not consult my application with Hughes when I ordered my rocker arms, BUT Hughes would not support me AT ALL when my rockers broke and I basically went to another vendor to buy the COMP rockers. Don't forget that not all rockers all have the same geometry, which means new push rods may be needed as well, so it's not as easy as JUST replacing the rocker arms.
Last note is to use high quality fasteners to hold down your rocker arms!
Posted By: MR_P_BODY
Re: RB rocker arms w/ roller cams - 06/03/14 10:40 PM
This is interesting.
Aren`t Jesel, Harlands and T&D Alum. Been taking my H&S`s past 7000 for years and I know of 8000+ rpm motors w/Alum. rockers.............
I have TONS of passes on my TD alum rockers with
WAY more open pressure.. mine is in the HIGH 800#
and turning 8200 rpm.. they have been in there for
a number of years... you buy cheap. you get cheap..
also I will say they did work to 9600 rpm but I didnt
have any power up high.. too small of a cam at .705 lift
Posted By: 68Bullet
Re: RB rocker arms w/ roller cams - 06/04/14 02:13 AM
I want to clarify my previous post. I'm not saying that all aluminum rocker arms are "guaranteed" to break. I'm just saying my aluminum rockers did break due to fatigue stress, and that now I personally trust steel rockers in my application (roller cam in a street car).
Now I do agree with the comment you get what you pay for. And with aftermarket speed parts like this, I've found that what you don't get is any support or warranty after the purchase. So do your research ahead of time and buy wisely. I believe '72CudaRacer is smart to be on this board doing just that. Which is why I'm just trying to give him at least one data point as reference. I personally have no experience with the new Hughes rockers or T&D/Jesel/Harland Sharp, but I'm glad to hear that others have had positive experiences.
Posted By: CompWedgeEngines
Re: RB rocker arms w/ roller cams - 06/04/14 02:47 AM
Hear what you`re sayin and as stated, comparing Dove to any of the mentioned bad azz rockers is apples to oranges and if you`ve been around long enuff you should of heard that by now...........
Right on Dom....
Posted By: Thumperdart
Re: RB rocker arms w/ roller cams - 06/04/14 03:48 AM
Just keepin it real...............big problem of mine I guess.........
