Grib: regarding the info in the one paragraph I've retained (below) from
your post:
I have no special expertise in this, but I wonder if the object of the very
large rocker ratios might be to reduce high RPM valve float and/or
pushrod-side valvetrain failure by making it easier for the lifter to
maintain intimate contact with the cam lobe(because the cam ramp angles are
reduced). On pushrod engines, most of the deflection and clearance
variation is on the pushrod side of the rocker; it stands to reason that if
you reduce the required travel distance on that side, (for any given RPM)
you reduce pushrod-side valvetrain accelleration and increase the
reliability of those components. Or you make the system able to run (with
the original reliability) at a higher RPM.
BTW, I think your postings about the NASCAR equipment (and what special
things those guys are doing with it) are very interesting. Please keep it
up.
Also-- NASCAR is not the only group running long connecting rods. I keep
running into them as I find out more about each of the worlds most
competitive professional motorsports. I'm beginning to think there might be
something to it.
Russ Mack
-----Original Message-----
From: owner-land-speed@autox.team.net
[mailto:owner-land-speed@autox.team.net]On Behalf Of rgribble
Sent: Thursday, November 28, 2002 7:09 PM
To: 'Dave Dahlgren'; 'Bob Jepson'
Cc: land-speed@autox.team.net
Subject: RE: SBC geometry
The other thing I noticed with NASCAR is they have generated to a very
radical (perhaps) rocker ratio. Yates runs 2.1 to 2.3 ratios and I am
told, this is to reduce the reciprocating weight. (I have 1.65 and 1.7
in the T'Bird) I suspect the cams look like they're worn out, but they
also run these engines above 9,300 PRM for 5 hours straight. It is
possible that with the loss of a "qualifying engine", some of these
designs may change. Any thoughts?
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/land-speed
/// what is needed. It isn't that difficult, folks.
|