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? ;=)
|