<VV> rocker ratios

Sethracer at aol.com Sethracer at aol.com
Tue Oct 11 11:45:35 EDT 2005

In a message dated 10/11/2005 6:58:16 AM Pacific Daylight Time,  
taruffi57 at aol.com writes:

Will  someone please give me again the ratio needed for the 140   rockers?

Joe Dunlap
Cen.  Fl.

Joe - All original Corvair rockers are designed for the same ratio it  seems, 
within minor production variances. About 1.5 to 1.57 to one. The actual  
ratio changes slightly during the travel. More at the beginning - Say, the first  
.1" of cam lift lifts the valve .157" . The last .1 of cam lift (Total lift at 
 the valve on most Corvairs is about .390) may only raise the valve .140" or  
less. This has to do with the geometry of the rocker arm and it's location in 
 between the pushrod and the valve. At the end of it's lift, the pushrod is 
still  moving vertically, but the tip of the rocker is moving mostly sideways. 
The  most important thing in this whole discussion - and I think both Lon and 
David  would agree (well, maybe) is to make sure that the rockers you end up 
using  on your Corvair motor were designed to meet the correct specs for the  
Corvair, or - in the case of many racing motors- designed to meet the revised  
specs based on the new cam/valve set-up. For many years I have been an 
advocate  of searching out older low-performance motors - for many years old 80 HP 
motors  were a drug on the market, available free - just haul them away. The 
rocker arm  assemblies on those motors, providing their oiling systems were 
maintained, are  hardly used, with low lifts, weak valve springs to work against, 
and low RPM  usage. Even if you recycled the motors, keep the rocker assemblies 
after an  inspection of the face. As pretty as roller rockers are, I cannot 
think of a  street usage for them. Matched original rockers should perform well 
for 99% of  applications. PS. All lift numbers above are very approximate and 
 guestimates - Your lift may vary! 
So - Whose going to start the discussion on pushrods?
- Seth Emerson

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