Icarus Valvetrain Upgrade

Now that I have had Icarus on the road for a while, I have been constantly tuning and refining it. Simply having it run is not good enough for me, I want it to be fast and indestructible.

Bear with me here. The Continental heads and rocker arms I used on the bike use automotive style rocker arms, unlike the harley style rockers most people are accustomed to. The original Continental boxxer aircraft engine from which these parts came used hydraulic tappets and solid pushrods, so it was a one shot deal as far as valvetrain adjustment. I prefer to have the ability to remove the pushrods from the engine without taking the entire head off, so I built some harley style adjustable pushrods. For those who don’t know, they are simply a male and female threaded rod, so that the length can be adjusted in order to collapse them enough to get in and out of the engine while assembled. In this case they also have oil pressure fed through them.

They worked fine, and survived several high speed test runs without any failure. However, that doesn’t mean they aren’t going to eventually fail. It is common knowledge that a solid pushrod is stronger than an adjustable one, but how to get them in and out of the bike without pulling the motor?

The answer is by removing the top section of my rocker box and loading them into the tubes from above. Unlike the stock Continental rocker boxes, mine are 2 piece so this can be done easily. I had previously converted to solid tapped blocks, so there now I absolutely have to have a way to adjust valve lash, but no longer have my adjustable pushrods to do it with. The solution is one that car makers have used for years- the adjustable rocker arm!

Of course, there are no commercially available adjustable rocker arms for a Continental 0 200, so time to get busy. I also decided to make the tips “roller rockers”, another trick from the car world. Here we go kids….

6061 bar stock..

machined to basic size. no CNC here…

roughing out basic shape…

I need a bronze bushing for the main pivot..might as well use the ones from the original rockers. Time to make a bushing pusher tool…

in press… comin’ out

pressed into new ones…

oil must travel through the rocker to oil the three critical points, so I drew some guidelines for the drill…

Holes are drilled, now time to cut the notch for the roller tips (taken from old Chevy rockers). Every tip is offset slightly.

Axle hole for the tip..

Stainless axles made and pressed in, securing the rollers..

Now for the adjustable end. I used some Chevy ball end studs, drilled through them, welded up the top end, and then cut a slot for a screwdriver…

All set.

Installed in head. Lash adjusted. Locked down. The welds on the end is where I had to plug a cross drilled oil hole.

Since the new rockers are bigger than the old ones, I had to make domed lids for my rocker boxes.

There you have it!



6 responses to “Icarus Valvetrain Upgrade

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