Barry & Tony,
The biggest enemy in making Hp is friction. The only time a bushing would have
less friction than a needle bearing is IF the bearing has a "full compliment"
of needles (no cage separator of the needles). With a full compliment needle
rocker 2 things happen:1. under load the adjacent needles are touching and
trying to rotate in opposite directions at the point of contact (high
friction). 2. In a relaxed state a full compliment needle bearing has free
space between the rollers. However, under load (full lift in our case) the free
space will be concentrated at the bottom of the rocker and the rocker
centerline will move up a small amount which is loss of lift at the valve.
Solution is to use CAGED needle bearings in the rockers and a proper fit and
hardness of the shaft. In the bearing industry (I have 25 years experience) all
balls, needles and rollers are hardened to 62~64 Rc. The shaft in our case
needs to be 60~62 Rc. The cage also provides a lube path for the rollers. I
have been making my own shafts for Spitfires for many years as well as
refitting roller rockers with caged needle brgs. . I also fab billet aluminum
rocker stands for Spits.
Ron Krantz
ReK Racing
> On November 27, 2017 at 6:51 AM barry rosenberg via Fot <fot at
> autox.team.net> wrote:
>
> Didn't NASCAR stop using needle bearing rocker shafts? The needles do not
> make a full rotation and wear more than bronze bushings.
>
> Barry
>
>
>
> On Saturday, November 25, 2017 10:30 PM, Tony Drews via Fot <fot at
> autox.team.net> wrote:
>
>
> Who sells the GOOD rocker shafts for wet liner TR-3/4 engines? It
> needs to be OK for needle bearings to run on.
>
> Mine came out in 2 pieces when disassembling this year.
>
> TIA
> Tony Drews
>
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