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Valve clearances


glynherron

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From what I've read, case hardening is typically to a depth of 1.5mm. The shims out there are from various sorces so unknown as to exactly how deep the hardening goes. I spoke to a local engineering shop, who specialise in 'older cars' who always grind the shims (albeit on a surface grinder with a magnetic vice). As I only removed 0.1mm I'm expecting that this will be fine. Time will tell... It's exhaust cam, valve number 4.

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TBH I've got a reasonable collection of these things - there is no evidence (colour) that suggests they are heat treated/case hardened after they are ground.  I suspect they are just a specific grade of steel.  

 

My engine has been running 'home ground' shims for the last 35k miles  with no issues

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Have you measured the gaps with no shims at all?

Suppose you have a gap of 60 thou with no shim at all and you are aiming for a 6 thou gap then buy a 54 shim that should then ensure the correct gap.

Not trying to teach grandma to suck eggs but obviously inlets and exhausts need different gaps Once you know the ballpark area you can buy a selection of shims either side to help with the best fit

John

 

That was my thought as well, but can't be done by the looks of it. Seems odd though.

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

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TBH I've got a reasonable collection of these things - there is no evidence (colour) that suggests they are heat treated/case hardened after they are ground. I suspect they are just a specific grade of steel.

My engine has been running 'home ground' shims for the last 35k miles with no issues

That's great news and extremely reassuring.

Thanks Barry. Working hard to create the time to finish her!

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  • Gold FFM

Tappet shims will almost certainly be a hard chrome-moly steel, so they're unlikely to be case-hardened.

Glyn, I think yours will be fine, and I admire your perseverance. I'm going to order the shims I need because I don't have access to a grinder.

I have found that what's engraved on the shim doesn't necessarily mean it's an accurate figure. I've had to regrade all mine, they were all a thou or two different, even taking into account any slight wear from the valve stem. And that can make all the difference!

Margate Exotics.

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