Thunda Babe

[WoodRay]

Some progress today with the CNC machining of the exhaust rockers. I'm getting more toey than a roman sandal.

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[Bob Vic]

Nice.... very nice work.

[WoodRay]

Thanks Bob. It's an exciting step finally after a lot of work and time. Im really looking forward to eventually turning the key but there's still a bit to go. I'm going to rework the lube system feed to the rockers so it's better regulated across both shafts.

[Will]

They look the part very nice -- There is soo much work in the design and build of parts like your rockers because you have left and right hand in both inlet and exhaust! Then a workable rocker ratio !
Are you going to use caged needle bearings with case hardened rocker shafts or plain bearings? - With needle rollers you would need very little in the way of oil supply - bit different if plain bearings - more friction more oil required

[WoodRay]

Hi Will, I'll be using plain bushes in the rockers. Due to the larger size of the caged needle bearings we wouldn't have enough meat left on the rockers to maintain strength. It's not so much an issue with the exhaust rockers, but the inlets are very tight for room. Once we get the inlets machined I'll post up a pick and you'll see.

[Will]

Ok I thought that would be the case
Another question - do you have to use a special cam grind with that head ? I don't mean a high performance cam because obviously you would - I mean do you need to compensate with the cam lobe offset to match the differences in pushrod / rocker angles between the inlet and the exhaust side.
Just asking because Ive never worked on a head with an asymmetric valves like this quite unique head which Im sure has its tuning challenges

[WoodRay]

No not at all Will. Phil Irving designed the head so it could be plonked straight onto a standard grey. A picture is easier to detail the set up. The valves were actually not completely crossflow, more diagonal placement in the chamber. This allowed for a larger valves compared to what the bore diameter would normally allow if hey were side by side. The only cam to piston issue was clearance on the inlet valve at it protruded lower than deck height on higher lifts. Duration changes could also be an issue. The high top pistons, if you opted for them, had a valve relief for the inlet valve. The standard cam was not a problem with the standard flat top pistons.

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[WoodRay]

Inlet rockers on the go today. Hope to have them all done by the end of next week. It will be decision time as to what I need to concentrate on for Narrandera.

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[Bob Vic]

What are your options Craig?

[WoodRay]

Option 1: If I get the rockers done next week I could possibly have the crossflow running for Narrandera. There's lots of fiddly stuff to do as yet.
Option 2: Alternately fit a better standard type head for Narrandera
Option 3: It's highly unlikely but push for the Seacraft for Narrandera