1.362 ratio rockers VS. TRUE 1.4 rockers....

[scott s]

 I haven't even torn into the 2276 yet (after I managed to break it again), but there's a chance I'll need a new cam during the rebuild. While looking over cam specs, I made a chart showing the advertised lift and the lift I would get with my 1.362 rockers (older SCAT 1.25's that measure out closer to 1.4).
  If a cam is designed for 1.4's and has a certain duration to match the lift, what happens when you have rockers like I do and lose some lift? For example, the cam in there now is like a K-10. It's supposed to have .549" lift and 310 degrees duration. With my rockers I only got .534" lift....about like a K-8. So, I have K-10 duration and K-8 lift. The cam made good power, but what am I missing?
  Would I be better off to get some true 1.4:1 rockers? It makes it hard for me to compare cams and make a choice with the set-up I have now. Or is there any advantage to this?

[Steve D.]

THERE IS NO SUCH THING AS A TRUE 1.4 RATIO ROCKER.  Differences in casting from the centerpoint in the valve guide boss and the location of the rocker studs is going to be different from head to head.  OEM VW vs. Auto Linea vs. Street Eliminators vs. Comp Eliminators vs. Super Flo vs. GME vs. etc....  Even core shift and machining tolerances can cause these distances to increase or decrease, effectively giving your rocker a greater or lesser ratio (longer or shorter arm).  Because it would be impossible for a manufacturer to make a set of rockers that rock 1.4 on every set of cylinder heads available, you end up with more lift for one guy and less lift for others.

To make things even more complicated, you can increase or decrease the ratio your rocker arms give you by tweaking the rocker geometry and adjusting where the rocker arm strikes the lash cap...

The 0.015" of lift you are missing out on is going to make less of a difference on how the car runs than whether or not you used the bathroom before you drove your car.

[Eaallred]

Right on, Steve. Some people are so concerned with who's rocker is the closest to thier 'advertiesed' ratio but don't realize that there are so many other things that come into play that affect it.

My Scat "1.4"'s come to 1.52:1 on my engine. They may be closer to 1.4 on another engine combo. You don't know the ratio until you bolt them on and measure it out on your particular motor.

[scott s]

 OK, makes sense...now, what about the cam. Any cam. If I KNOW I have a "smaller" rocker, should I be concerned with the duration on the cam since I "lost" some lift? Or should I just get a bigger bladder?

[Steve D.]

My Scat "1.4"'s come to 1.52:1 on my engine.

Comp. Eliminators?

[turbo_bob]

THERE IS NO SUCH THING AS A TRUE 1.4 RATIO ROCKER. Differences in casting from the centerpoint in the valve guide boss and the location of the rocker studs is going to be different from head to head. OEM VW vs. Auto Linea vs. Street Eliminators vs. Comp Eliminators vs. Super Flo vs. GME vs. etc.... Even core shift and machining tolerances can cause these distances to increase or decrease, effectively giving your rocker a greater or lesser ratio (longer or shorter arm). Because it would be impossible for a manufacturer to make a set of rockers that rock 1.4 on every set of cylinder heads available, you end up with more lift for one guy and less lift for others.

Good explanation Steve. That is why Gene Berg used a stock VW head and stock VW cam when setting up there ratio rockers, to get as close as a true 1.4, 1.45, 1.5 ratios using stock components. The side effect of doing it this way, when the user uses a aftermarket performance cam there ratio will allways be more than advertised.

[scott s]

My Scat "1.4"'s come to 1.52:1 on my engine. They may be closer to 1.4 on another engine combo. You don't know the ratio until you bolt them on and measure it out on your particular motor.

 When I first had this engine built I had some of the older SCAT 1.4's. Mine measured out at over 1.6! That's why I swapped them for the "1.25"'s which were actually 1.36XX

[A.J.Sims]

A long cut push rod would give you a higher ratio rocker. The adjuster is moved up and closer to the center line changing the ratio.
Got this info from Doug Berg!

[Eaallred]

Comp. Eliminators?

Bingo 

[Kevin Alexander]

Interesting, I never knew the pushrods could have an effect on rocker arm ratio. So if a longer pushrod caused the ratio to be higher, I take it a shorter one would make it go down?

[Bruce Tweddle]

The same reason why a longer pushrod causes the ratio to be higher is why a cam with more lift causes the ratio to be higher.  That is why rockers are always a higher ratio than the mfr stated.