Roller Rockers
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From: Mesa AZ
Roller Rockers
I am confused about the rocker arms on my 04 C-5. People refer to them as roller rockers. However, pictures seem to indicate that these are partial rollers. The only roller is the trunion part. I think my 1996 Grand Sport (LT-4) has full rollers produced by Crane. Am I correct about all of this? If this is correct, why would GM not use full rollers on the C-5. Does the C-6 have full rollers? Maybe it has to do with the redline on the Lt-4. Any ideas?
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They are not true roller rockers. I'm not sure why the factory didn't use true rollers. You can install yella terras, harland sharp, etc... if you want true rollers. Some people have had an issue with the stock rockers spilling their needle bearings, especially after continued high rpm use. Others have done just fine with the stockers.
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Even the LS7 or LS9 has what you have (although the intake rocker tip is offset for geometry of valve placement) -The GM slider tips, only the fulcrum has roller bearings.
They are roller fulcrum.... But not full rollers. and another thing... it's been proven that valve lift over .550 requires full rollers shimed correctly for geometry. Bolting up stock rockers will lead to (issues) such as valve guide wear, burnt valve tips, and possibly broken springs over time. You can trash a nice set of heads with the wrong rockers.
They are roller fulcrum.... But not full rollers. and another thing... it's been proven that valve lift over .550 requires full rollers shimed correctly for geometry. Bolting up stock rockers will lead to (issues) such as valve guide wear, burnt valve tips, and possibly broken springs over time. You can trash a nice set of heads with the wrong rockers.
Last edited by ~Josh; Jun 19, 2009 at 09:07 AM.
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From: Mesa AZ
Thanks for the info on the roller rockers. I guess the General did not want to spend money for full rollers, if it were not required to meet factory durability requirements. As best I can tell, the LT-4 engine must have been designed for a bit higher rpm.
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My thoughts...
With that being said, GM wanted to send the Gen II small block out with a bang (LT4) with the added extra rpm they needed a more robust rocker arm compared to the cheap 1.5 ratio stamped units used since '55.
Cheap stamped rocker:
Without investing money in R&D for a better rocker to handle the extra stress of the LT4's intended rpm... they decided to outsource (buy) full rollers from Crane since the Gen II engine program was on it's way out anyway. It was a limited production run.... and in my opinion, they made a great choice.
They did spend the money on better equipment for upcoming Gen III since it was a long term future powerplant. Not full rollers mind you... but better than before.
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Thanks for the additional information and picture. I have seen the Rollers on my GS engine and they are really nice pieces of work. One can coax a lot of power out of the GS engine, but as with others, it costs.
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From: Machineguns, because I don’t compromise
Running .600+ lift with stock rockers is flat out rediculous. Full roller rocker arms (full ark) have HUGE advantages over slider tip (partial ark) units. And it has nothing to do with aluminum.
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St. Jude Donor '03
Slider tip rockers are limited by geometry. Running more than .550 lift on stock LS1/2/6 rockers means the user has no idea what he's doing to his valve guides, etc.
Running .600+ lift with stock rockers is flat out rediculous. Full roller rocker arms (full ark) have HUGE advantages over slider tip (partial ark) units. And it has nothing to do with aluminum.
Running .600+ lift with stock rockers is flat out rediculous. Full roller rocker arms (full ark) have HUGE advantages over slider tip (partial ark) units. And it has nothing to do with aluminum.
It was a glorified advertisement for Trickflow, with zero actual data backing it up, only theory and cute drawings.
Going on 4 years with .615" lift on stock rockers...no problem here!
BTW, aluminum rocker bodies are VERY susceptible to fatigue failure, that's one reason GM chose steel...
The other is they are very light over the valve, much moreso than any roller-tip rocker available today. No need for a crazy-heavy dual spring to support them in the fight against high RPM valve float.
The OE valvesprings and pushrods are the weak links the valvetrain. Upgrade both, and it will be stable to 7500+ RPM easily. Riocker arms included.
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Honest question...Too many people have proven otherwise, I'm curious to see the other side of the claim.
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From: Machineguns, because I don’t compromise
In my own engine swapping to 918 springs with a new cam (.588 lift) the valve had almost no play within the guide. After 20k miles doing a routine spring swap checking the same play... A very fair amount of wiggle room.. in just 20k miles. So... it went from almost nothing on a virgin with 30k miles to "loose" with another 20k.
Not a single cammed car has had super tight spec (by feel) like a factory spec would.
I have nothing on paper, but I know.