<VV> Roller Rockers V8 vs. Corvair specific

[Sethracer at aol.com]

In a message dated 11/25/2006 8:07:51 AM Pacific Standard Time,  
roadrashgixer at msn.com writes:

I   hate  to interrupt, but can anyone that has a set of roller  rockers
on their Corvair, tell me if they are worth the  money?  Mine will be a
Sunday  driver.   I  just wonder if they are worth getting a set.  What
kind  of performance or longevity would I see?
And  can anyone  tell me just what the difference is between SBC roller
rockers  and the Corvair roller rockers?  I've heard several times  that
they are different, but that's all.  How do they  differ?
Thanks,
Chad 1969  Convertible



There are four main differences between the small block Chevy rockers and  
the Corvair. First, the "ratio" of the rocker. The "ratio" of the rocker is the  
distance from the rotational point of the ball stud mounting to the "average" 
 contact point on the valve (Average during travel from valve closed to open) 
 divided by the distance from that same rotational point to the theoretical  
contact point of the pushrod tip in the other end (which also changes during  
travel). However, the real-world ratio is how much vertical travel the valve  
makes from closed to open divided by the lift of the cam lobe (as represented 
by  the vertical movement of the pushrod as pushed there by the lifter.) 
(vertical  in relation to the contact point on the cam) On a Corvair, that 
direction is  almost horizontal. Corvairs have an effective ratio of about 1.57 to 
one. Small  block Chevy has less in their stock lifters - More importantly, the 
actual  distances in the small block rocker are less. The distance from the 
ball stud to  the tip and the distance from the ball stud to the pushrod are less 
than on a  Corvair. Their ratio is close, but the distances are less.  The 
second  difference is the oiling method for the ball stud. On the V8, the 
pushrod is  above the ball stud and the valve tip. The V8 rocker passes oil through 
the tip  of the pushrod and the oil squirts out a hole in the bowl where the 
pushrod  seats, then drips to the ball stud and eventually onto the tip of the 
rocker  where it lubricates the valve contact area. The Corvair Rocker is 
upside down  from the V8, the pushrod is beneath the ball stud and the valve. If 
the small  block design was used, not enough oil would reach the ball stub or 
the valve  tip. The corvair rocker has no hole in the tip bowl, where the 
pushrod seats. It  has a hole in the body of the rocker, approximately adjacent to 
a hole in the  pushrod that squirts oil out under pressure. As the pushrod 
rotates around, the  oil squirts upward through the hole in rocker and lubes the 
ball stud, living  right above that hole, and the tip of the rocker, living 
just above that. So the  Vair rocker has two oil related differences, no hole in 
the tip, and another  hole in the body. Finally, the Corvair uses the Chevy 
style self-aligning ball  stud rocker. But the small Block Chevy V8 valves are 
parallel in the head. All 8  valves live in the same plane. Although the 
lifter to lifter distance is  slightly different than the valve to valve, there is 
almost no mis-alighment to  be "made-up" for in the rocker. The Corvair has a 
slight "Porcupine" valve  system (Way before Chevy's Mystery V8 in NASCAR) If 
you look at the  slot in the bottom of the Corvair rocker, you will see it is 
wider than the V8  rockers. This is because the Corvair rocker has to live in 
both the Intake Valve  arena - accounting for the lean to the left and the 
Exhaust arena, leaning to  the right. So the rocker has to self-align to the vale 
and pushrod locations,  which change during the travel of the pushrod and 
valve, lean over to maintain a  flat contact with the valve tip, and rotate to 
account for the "porcupine style"  (non-parallel) valve gear. The V8 can use 
straight trunion rollers because  the pushrod and the valve are in the same 
plane, and most aftermarket V8 rockers  rotate in only one plane. The Corvair 
rockers are special. That is why the  Corvair rockers have special intake and 
exhaust and even special 140 rockers,  since the plane is different in the 140 
head. SO there you have it. Stay with  the special Corvair rockers, either closely 
inspected used rockers (keep the  mated ball with the rocker) or aftermarket 
ones that are properly designed for  the Corvair engine. One final tech tip. 
If you find an old 80HP motor about to  be recycled, grab the rocker arms and 
rocker balls. If they were properly oiled,  they have the best potential for 
the lightes usage - low lift cams and low  RPM. Good donor material! - Seth  
Emerson