Risking

Rb26 Cam Base Circle, Valve Clearance Issue

8 posts in this topic

Im fitting Apexi 270/11.4mm cams to my new RB26 head. I have releived the casting, cut valves, new guides etc etc.

Now come time to set the valve clearances the apexi cams use significantly smaller base circle.

The old Poncams had a base circle of 32.00mm which is obviously same as the OEM cam.

The New Apexi cams have a base circle of 30.40mm.

Majority of my existing shims are 2.80mm which is fine.

However the base circle is 1.6mm smaller than the original meaning I have to increase all my shim sizes by approx 1.6mm.

1.6mm on top of the original 2.80 is 4.40mm. The largest shims Ive seen are those CRD are selling which are 4.30mm.

So im asuming I have a few options, make my own shims to suit that are roughly 4.40mm (obviously made to exact size I calculate) OR........ im open to suggestions on the situation.

Thanks In advance Brad.

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do apexi make shims to suit? like tomei do with their cams...

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do apexi make shims to suit? like tomei do with their cams...

No not that I have been able to find. Its only .1mm larger than those that CRD are selling and I have the equipement to grind my own shims from a suitable material so its looking like ill take that path as the tomei shim kits start getting expensive.

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small base circle Jun cams

as above, my jun cams needed either shims or buckets, i got the buckets, same either way.

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Thanks Proengines, Ill be speaking to chris about doing this.

Any idea what thickness shim you went up to??

Im running apexi retainers which seem to have a much taller recess for the shim, obviously to aid with holding the thicker shim in position.

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I think he lists them to 4.4 but can do thicker from memory.

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