PRO: Dan Weseman, Florida, 400 hrs on 3,100cc Cleanex, 125 hrs on 3,000 cc Panther. These went with the little T-handle hold downs bolts on valve covers) and second was to allow the use of a device called a ‘Stud Girdle’ that clamped the tops of all the Poly-locks rigidly together to prevent the from flexing when using combination of very high lift, very high spring pressure and astronomical rpm limits, none of which is ever remotely seen in Corvair flight engines. Most builders and car people don’t understand the two reasons for the existence of Ploy-locks are very rapid adjustment of the clearance on mechanical lifer cams on V-8s (This is not for maintenance, it is to alter the power delivery on the engine, often to suit traction conditions in drag racing. Roller rockers have their own adjustment nuts called “poly-locks” It is basically a threaded tube with an Allen set screw up the middle that jams on the top of the stud. (The studs that Langford and I used were made by ARP in California, and the current Clarks item looks visibly different, but I don’t know their origin.) They must have deeper than stock valve covers, custom length pushrods and Poly-locks.
They need to be mounted on longer rocker studs, commonly sold by Clarks as #9295. When installing roller Rockers several other items must be changed. Other builders followed this with even more hours, notably Mark Langford who eventually flew more than 1,000 hours on the same set without issue. They worked, but just as I predicted, no change in power nor oil temp. We flew it several hundred hours and checked the valve train intermittently. I bought a set just to test, and when our 601XL flew in early 2004, I am pretty sure it was the first Corvair powered plane to fly with roller rockers. Part of the internet hype at the time was roller rockers lowering oil temps and boosting power in Corvair engines. H-S didn’t have a website as late as 2003, but they directly sold to builders and they were a lot cheaper than SC Performance, which carefully trimmed the H-S name off the packaging before marking them up for resale. Because I spend my youth on NJ drag strips like Englishtown, Atco and McCarter highway, I instantly knew they were made by a company in the middle of America called Harland-Sharp. However, the first time I saw an SC performance rocker in person, I saw it was orange in color. This all seemed reasonable in a black and white photo. Back more than 12 years ago, there were several Corvair car parts outfits like SC performance and Clarks selling roller rockers, and most of the literature implied that they were developed by these companies. They were never designed with simplicity and longevity in mind.
First, a bit of history: Roller rockers were developed to replace ball types so V-8s could use 7,500 rpm and cams with. While they are made in America and very fine quality, there are actually some pros and cons to using them in a flight engine. Builders: In the discussion of rocker arms, the subject of roller rockers comes up occasionally as an alternative to the stock ball type.