OHC Tappet clearances

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martinng
Posts: 147
Joined: Thu Oct 10, 2013 5:31 pm

OHC Tappet clearances

Post by martinng »

I was Just having a look around the engine by way of a general inspection after the long run last weekend.
Good news compression is 75psi on each cylinder so that's excellent, the ignition is set up well now that I have removed the the oil from the distributor and installed rubber boots on the HT leads.
This brought me to looking at the tappets.
I have measured these (cold) and they are .012" except one at .010" and another at .008" (both exceptions are valves on the manifold side).
So what should they be? The standard Minor OHC should be "not less than .003" - probably a 'hot' figure. My engine has been rebuilt around what I now discover is an MG J block, so there is a suspicion in my mind that some kind of MG cam may be fitted. All the MG data (ref: Timing Chart from Tripple M Reister website) for cold clearances for J-types indicates inlets at 006" and exhaust at 008" and M-type .004" for all valves.

I need to establish exactly what camshaft I have, but in the meantime is there a clever technical person who can tell me please what is the effect (is it damaging) of running with clearances that are too large?
Also which way round are the valves. There are two rows of course, so are inlets on the manifold side or distributor side?
Martin
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