Jim Miller, MID-LIFT Geometry, Rocker Arms, Race Engine Parts

CROWER Cams denounces MID-LIFT Geometry, then secretly tries to adapt it and call it a "Better Geometry"...

What does this backsliding mean to the ever trusting Engine Builder?

For decades this has been an example of the leading technology sold by one of America's oldest and most well known names in racing: Crower.

This example has been purposely set in perspective as shown to the right, with the roller centerline of both the roller and shaft on the horizontal plane; dubbed the "Motion Line."

What needs to be noted, without the clutter of the lines shown to the right, is how HIGH the bottom of the push-rod cup is above the shaft CL.

This is the vaunted "stainless" steel Crower rocker arm that has been used for many years. It is impossible to set the geometry "correctly" with what Crower now calls a "better geometry" (MID-LIFT by another name), without suffering this very bad over-arcing illustrated by the pushrod's actual tangent points, shown by "A" & "B".

What's sad, is that this rocker is no longer available without explanation, and it was replaced with a "better" design that had the same part number. Until we politely brought the injustice of this for engine builders to their attention.

Today, companies under pressure to explain the mistakes of their various rocker arm designs fail to define what rocker geometry really is. Instead, they have resorted to misinformation and renaming products, apparently in the hope that no one will notice. Crower's now extinct part number above, is a prime example.

When the MID-LIFT Patent was issued in 1982, many companies didn't even know about it, or didn't recognize the significance of it, until years later. (See: The LUNATI Factor) If they admitted the inaccuracy of their designs then their credibility as a leader of whatever they promoted would suffer.

Crower Cams, chose to denounce MID-LIFT geometry in 1999, at the same time they were trying to quietly change their over-arcing rocker designs to MID-LIFT concepts, which they started doing after reading an old 1992 article in Car Craft Magazine by Chevrolet's "Race Shop" engineers. Crower's 2002 catalog showed illustrations duplicating Miller's MID-LIFT principles and referred to it as a "better geometry."

Crower produced a stainless steel rocker arm for decades. Even though it was typical of the industry's inaccurate and over-arcing geometry, it opened the valve. When an article appeared in a 1992 issue of Car Craft from the Chevrolet Race Shop, it gave Crower's long time brother-in-law and appointed rocker arm designer, Loren Harris some enlightenment that previously had alluded him and the Crower staff. Finally in 1996 or so, they began redesigning their rocker arms from this information. This was good. Except, first of all they were infringing on the long standing MILLER Patent; and second: when they started to change their designs, they didn't even bother to assign a new part number! Do you think this mattered to Crower? They were obviously too interested in "quietly" fixing their old designs, and we guess they never considered an engine builder might some day replace partial sets during an engine rebuild. I guess Crower wasn't concerned if the change meant that the old pushrods were now .150" TOO LONG! Probably just going to sell those in partial sets... under the same part number.

Point In Fact: The Commissioner of Patents & Trademarks doesn't issue Patents on "opinions."

MILLER PRODUCTS GROUP
1775 Blount Rd. #413
Pompano Beach, FL 33069 USA

954-978-2171

"MID-LIFT" & "PRO-SHAFT" are Ž Registered Trademarks of MILLER ENGINEERING INC; Copyright Š MMIII - MMX JM Miller