<VV> Re: rocker arm ratios

[N. Joseph Potts]

I have a FEELING that the level of precision effectively required in this
situation entirely leaves out the digit representing hundredths in the
ratio. Working in the inches the Corvair was dimensioned in, we're
accustomed, particularly where the engine is concerned, to working in
thousandths of an inch, three digits to the right of the decimal point.
Reflexively applying the same nominal precision to the ratio delivered by
the rocker arm from the pushrod to the valve may be a complete mistake. I'm
very open to the idea that ANYTHING in the range 1.5 to 1.6 may be JUST FINE
for a stock Corvair engine. Now, where we start cutting steps out of heads
and reducing deck height to zero, closer tolerances seem to call attention
to themselves, but even there, the ratio may not become more critical - just
the height of valve lift.
     All this, if valid, relegates the significance of David Herrin's
discussion to cutting-edge racing and precision-mad zealotry.

Joe Potts
Miami, Florida USA
1966 Corsa coupe 140hp 4-speed with A/C and (probably) SBC rocker arms

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org]On Behalf Of BobHelt at aol.com
Sent: Sunday, October 09, 2005 11:48 PM
To: djtcz at comcast.net; virtualvairs at corvair.org
Subject: Re: <VV> Re: rocker arm ratios

Yes, the early model Chev literature does say that the rocker ratio is 1.50.
But most Late Model literature states a 1.57 ratio. Why the change? Who
knows?
Other Chev data seems to be confused too. How about 1.53?

Tests run by several Corvair nuts have shown that all stock rockers had the
same ratio, probably 1.57. The only way to know for sure would be to run
some
tests on several stock engines using TWO dial micrometers, one at the
pushrod
and one at the valve stem to measure lifts. Then do a calculation.
Regards,
Bob Helt