On 10/17/2013 3:45 PM, John Hasty wrote:
> What is the group's wisdom on roller rockers for a 4 motor.....assume it is
> not "stock" & has a billit crank, proper rods etc?????
>
I suppose it depends primarily on two things--what the roller rocker
weighs compared to stock, and the intended maximum rpm. There's
probably a marginal increase in valve guide life--if they're set up
properly--pushrod length/pedestal height is just as important as with
stock rockers. The roller rockers I've seen, although from 6061-T6
aluminum billet, actually weigh _more_ than the stock rocker, so the
advantages of reduced friction are offset by the need for somewhat
stronger valve springs to maintain the same point of valve float, and
that latter disadvantage increases with the square of the rpm.
That said, virtually all makes are CNC machined today, so there's a
uniformity to them that isn't present in the stock rockers. One can go
through dozens of stock rockers to get a set that has a uniform ratio
and weight. And, beam strength counts as the rpm goes up, and modern
roller rockers are superior in that regard. If you're redlining the
engine at or near 6000, I doubt you gain anything by using roller
rockers over a well-prepared set of stock rockers, but, if you're aiming
for stratospheric rpm, roller rockers are probably a necessity, since
stiffer valve springs are usually required to reach those higher revs,
anyway.
Cheers.
--
Michael Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking distance....
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/archive
|