Broken Rocker Arms-consistantly?
05-14-2008, 11:57 PM
#16
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Colin Belton from 9M in England has machined from solid billet rockers that are DLC coated. I would check there. They also have revised geometry so you can run a larger than .525" camshaft which is about the practical limit of the stock rockers. However, if you are breaking the rocker ams with the regularity posted above, I would have to look at something mechanical in the valvetrain.
05-15-2008, 09:54 AM
#17
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funny u mention the early rocker substitition. I "scrounged" and found several early (pre-cast) rockers the other day as part of the "price is right curtains', you know; what's behind curtain 1, now what about the other two? . I am now (today) putting this "thing" back together. I will conclude within the time of "coffee break" as to what I'm installing. I DO believe in the cast rockers, I HATE the buttons! I know I'm running a bit of extra lift too....Ahh, guess we'll see....Watkins Glen next week will the moment of redemption or continuous road to pergatory.....Sucks as I've got so many other jobs to concern myself with! NYC-dingy day!-M signing off
05-15-2008, 10:54 AM
#18
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I suffered for 18 months with this exact problem. I used modified 993 hydralic rockers with the solid adjuster and they would break randomly between 30 minutes and 20 hours. The modified 993 rocker looked sometimes as though the shaft was startiong to pick up in the bore, the earlier bushed ones did not show this. I tried standard rockers, shot peened and polished and these did not seem any better and like you I thought I would have to go with the Porsche race rocker. I have lots of these so it was not a money issue its just they are such a pain in the ****! Of course, I use the later cam carriers from the 993 with the pressure lubricated rocker shafts. Don't try and use 993 rockers in the early carriers as even if you drill them for lubrication the pad on the end of the rocker can run off the cam!
Before I tell you what was the solution for me I should tell you a little about the engine. Its a 3.4 litre twin turbo runing boost between 0.8 and 1.2 bar. Power is significant as you may imagine! I use a Porsche cam profile from an old IMSA spec 2 valve 962, centre lubricated, so I suspect it is not far from yours in terms of overlap and lift. Sufice to say its pretty severe!
I fixed these problems over the winter by investing in a set of Porsche 993 RSR adjustable race rockers and DLC coated shafts. They are very light and so far appear very strong. I compete in the UK Britcar championship and the engine has already done around 22 hours this year without any rocker mishap. I took the top end down after 15 hours as part of our standard maintenance and everything looks good.
I can't say this will cure your problem but it did mine. Trouble is the parts are a silly price!! I can find the motorsports part number if you want it.
Good luck.
Richard.
Before I tell you what was the solution for me I should tell you a little about the engine. Its a 3.4 litre twin turbo runing boost between 0.8 and 1.2 bar. Power is significant as you may imagine! I use a Porsche cam profile from an old IMSA spec 2 valve 962, centre lubricated, so I suspect it is not far from yours in terms of overlap and lift. Sufice to say its pretty severe!
I fixed these problems over the winter by investing in a set of Porsche 993 RSR adjustable race rockers and DLC coated shafts. They are very light and so far appear very strong. I compete in the UK Britcar championship and the engine has already done around 22 hours this year without any rocker mishap. I took the top end down after 15 hours as part of our standard maintenance and everything looks good.
I can't say this will cure your problem but it did mine. Trouble is the parts are a silly price!! I can find the motorsports part number if you want it.
Good luck.
Richard.
05-15-2008, 01:00 PM
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spot on
Your input has been spectacular(RICHARD) in firming up my conviction that the fairlue(s) have been created by running a cast rocker and cam combination. Steve and the "gang" have helped in creating this most frustrating yet informative thread too. Had it not been for them keeping me participating, Richard may not have noticed this discussion. While I would prefer an adjustable rocker, I'm pretty much out of time. I am going ahead and installing button rockers along with the pain they will cause upon installation. For all of "us", take note-this particular configuation of this engine we "bastardize" must never use adjustable cast rockers. Steve's comment on the early rocker was great except for the fact the I've only 4 left from the "early dayz" (UGH!)
I do PROMISE to let u guyz know how this turns out in a few weeks-It'll take me that long to get twelve buttons to fit this in a mid-engined car, even with my old tricks. :-) tanks too much-Mark-sunny day in Nueva York!
I do PROMISE to let u guyz know how this turns out in a few weeks-It'll take me that long to get twelve buttons to fit this in a mid-engined car, even with my old tricks. :-) tanks too much-Mark-sunny day in Nueva York!
