Thunda Babe

[Will]

Just did a quick theory check on linear expansion differential between Aluminum and Cast iron -varies a bit with alloys - AL is twice CI so @ 200F the difference is 0.0012/inch of spacer length. Alans idea is good tho - if the spacer grows say 0.010 then the CI would grow half that (0.005) so to have 0.002 clearance @ operating temp the space would need to be 0.007 less than the measured dimension at ambient.
However the width of the Rockers also needs to be factored in
You can se why the Poms use springs as spacers in a lot of the older engines - rocker width and pedestal tolerances become inconsequential

[WoodRay]

Springs aren't an option as I can't afford to have the rockers walk sideways off the valve tips at high rpm. Also the shafts are only 5/8" so the spacers are also added rigidity to prevent flexing especially with the exhaust shaft. Good to know the possible dimensional changes I could expect. Thanks.

[Greg]

Out of my depth here, but what about using the spacers and Belleville washers?

[WoodRay]

Out of my depth here, but what about using the spacers and Belleville washers?

That's an idea Greg. I'll keep that in mind. I'll be doing several tear downs as we get the hours up on the rockers so we can check for any issues and wear. I'm actually happy for some gap when cold as this will allow some initial oil to escape for splash lube of roller tips, adjusters, and cooling of the springs. As the oil thins with heat and the gap closes up this should keep the oil loss regulated without affecting the main pressure to the bottom end components. It's just finding the right cold clearances to start with.

[WoodRay]

Well that was a fun couple of days. Head is ready to go on bar one water bleed fitting. There is very little room within the valve gear to run tube work for my external lube supply so it took a few goes and some trickery. I think it'll work OK.

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[rayza1]

Thats looking shmick Craig, so much detail!!

[WoodRay]

Knocked up temporary zoomies today.

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[Greg]

Very nice indeed, Craig

[WoodRay]

Very nice indeed, Craig

To be honest I'm not really a fan of them Geg. It'll have to do till I get the stainless sorted and I actually make up my mind with how I really want the exhaust system. I just have to find my mind first...................

[Greg]

I loved 'em on Impact. What a noise!