Simon,
That's a great explaination. Rookie curiosity satisfied!
Andy "Anybody Wanna Paint My Car?" Ramm
'67 MGBGT still no paint, still no roller rockers.
Simon Favre wrote:
>
> See my $0.02 worth below...
>
> Andy Ramm wrote:
> >
> > OK, I'll pipe in with a few boneheaded questions, I'm a rookie, so
> > please go easy on me....
>
> Aw, shucks. No roasted rookie for lunch. ;=)
>
> > I'll first say that I understand completely the motive of vintage racing
> > to keep things in accordance with period technology and I wholeheartedly
> > agree with that. However, I'm a little troubled by the roller rocker
> > issue.
> >
> > It seems that the overall benefit of roller rockers has more to do with
> > valvetrain reliability and longevity than performance. Am I wrong?
>
> Afraid so. The roller rockers (and roller cams) allow the motor to turn
> a lot more RPMs without becoming a grinding mill for old parts. They
> also allow even wilder cam profiles, and higher rocker arm ratios. This
> is one area where you can add a LOT of HP.
>
> > It also seems that with all of the things you can do to cheat (and I saw
> > several obvious ones at the Sears Point CSRG event) that roller rockers
> > are one of the more benign. If I could, I'd run rollers just to spare
> > the valvetrain additional wear and reduce the possibility of failure.
>
> So just how high are you over-revving that motor? ;=)
>
> > Should we also outlaw synthetic lubricants? Should we make everyone run
> > on bias-ply tires? Should urethane and nylatron bushings be outlawed?
> > What about breakerless ignitions?
>
> Without synthetic lubricants, many of these motors would need to be torn
> down after every race, just like in the old days. This is a hobby, right?
> We're not doing this for prize money, right? Even though synthetics will
> allow the motor to rev higher, and give back a few percentage points on
> the HP, they don't make the power. There's no point subjecting everyone
> to a lot of added expense and time wasted just to be able to say we did
> it all on dino juice. Unlike your MGB, some of these parts don't grow on
> trees. <sarcasm alert>
>
> The cars that also run with HMSA may indeed run on bias-ply tires. I do.
> Harder plastic bushings are still a lot more compliant than Heim joints.
> Breakerless ignitions are one thing, crank fire or distributorless is
> quite another matter. A breakerless ignition doesn't re-map the advance
> curve. One distinct advantage of having an MSD or similar system is the
> rev limiter. That really will save a motor. You mean you never missed a
> shift? Honest? Since there were hot coils back then, it seems reasonable
> to allow a system that still uses the distributor, complete with primitive
> advance mechanism, even if it has been re-curved. There's only so much you
> can do with a couple of weights and springs.
>
> > I don't mean to entirely impune the no rollers rule, but I guess I'm
> > seeking a better understanding of why the rule is still in existence for
> > many groups.
>
> For most cars, the presence of roller rockers implies that there's a lot
> more even deeper in the motor. Roller rockers are like the tip of the
> iceberg. If they see roller rockers, they are certain there's an iceberg
> underneath. Of course you have Titanium valves sitting under those roller
> rockers, right? ;=)
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