A Look Into Jon Kaase’s Shaft-Mounted Rockers for Big-Block Fords - Engine Builder Magazine

A Look Into Jon Kaase’s Shaft-Mounted Rockers for Big-Block Fords

At first glance, Jon Kaase’s new shaft-mounted rocker arrangement for his P-51 big-block Ford cylinder heads conveys stability.

To the competition valve train, it contributes both strength and accuracy. However, the new arrangement possesses many more appealing prospects, some of which are concealed.


For example, the 0.900in wide aluminum rocker bodies are characterized partly by their 1.650in pivotal length, but mostly by their twin needle bearings. The disadvantage of using a long, single needle bearing with canted valves is that, under high spring loads, the forces tend to skew the needles. As a consequence it drives them into the end of the bearing case and failure soon follows.

Beacon of ingenuity
As usual, a stroke of genius intervened. Two short needle bearings were introduced: one 1/2in wide (installed on the trunnion’s loaded side), the other 3/8in. This layout provides a space of 0.025in between the bearings which is used to deliver lubricating oil via a hole in the top of the rocker—a feature not possible with a single bearing. When a solution passes the scrutiny of accomplished rocker specialist Wilfred Boutilier it is apt to be good.

Successor to the traditional stud-mounted rocker, this new arrangement is also distinguished by its one-piece stand with integral cant angles, which accommodate the rockers operating the intake valves. The U-shape exhaust stands are individually formed and secured to the existing mounting pads of the cylinder heads.

To prevent the exhaust stands from rotating during assembly or in operation, they are angle-milled to four degrees on their back face. This formula ensures they lock against the adjacent face of the intake stand.

No shimming required
Though the popular rocker ratio of Kaase’s P-51 is 1.75:1, alternative ratios are available from 1.73:1 (original specification) to 1.80:1. Moreover, the rockers operate on a pivot shaft hardened to around 60Rc and because they are designed specifically for the P-51 racing heads they require no shimming—the rocker geometry is exact.

When Kaase first introduced the P-51 cylinder heads, he extended the valve stems by 0.100in compared with those of the Super Cobra Jet head, which he also designed. Of course, longer valves permit longer springs which, in this case, allow engine tuners to achieve valve openings of up to 0.800in. without the threat of valve springs reaching their coil-bound limits.

To most observers, the success of Kaase’s P-51 cylinder heads, which came to prominence around 2008, is often attributed to their unrivalled power for the money. Their induction ports possess abundant air flow and their combustion chambers with their intake valves moved closer to the ports, are efficient. But the big thing is they operate with standard intake and exhaust manifolds, which represent substantial savings for any Sportsman racer.

You May Also Like

Volvo Penta’s D17 Industrial Engine

The 17L diesel engine uses dual-stage turbochargers and heavy-duty steel pistons, making it optimally designed to power a wide range of generator sets.

Volvo Penta’s most powerful engine – the D17 – supports the current business needs of industrial customers as well as future demands as they navigate the energy transition towards decarbonization using renewable fuels. This is just one reason to choose the D17 power generation engine. Read on to discover a whole lot more.

Kingdon Drags Joins IHRA

This adds recognition to Kingdon Drags, and the track is proud to fly the IHRA colors.

Mahle Appoints Brent Fletcher Head of North America Aftermarket Regional Sales

Fletcher and his team focus on dialog with customers to position Mahle as a strong partner in aftermarket business.

NASCAR to Launch In-Season Tournament in 2025

The top 32 drivers based on the seeding events will become eligible for the in-season tournament competition.

Ned Walliser Elected WPI Board President

Walliser was elected to a three-year term during the company’s annual shareholders meeting last month.

Other Posts

All About Diesel Fuel Lines

There’s more than might meet the eye when it comes to diesel fuel lines.

fuel lines
Fire Rings for a Better Sealing Diesel Engine

As the typical diesel engine continues to see more performance, a simple job like fire ring installation can go a long way toward keeping your engine together and working properly.

fire ring block
Pennzoil and IndyCar to Launch New Race Oil at Indy 500

Pennzoil’s new racing oil to help reduce greenhouse gas emissions throughout NTT IndyCar Series.

Pennzoil IndyCar Performance Oil
Enginetech Headache Kits

Each Enginetech headache kit is customized to fit different vehicle applications, so the contents will vary.

Enginetech kit