John,
The TR7 uses the "bucket and shim" valve adjustment system similar
to what is used on some motorcycles and, I am told, Jags. The TR7
is overhead cam where the cam acts directly on the valve. The cam
lobe rides on the "bucket", a cup shaped piece metal which fits over
the top of the valve/valve spring assembly open end down sort of like
a cap. The shim fits in a recess inside the bucket where it contacts
the valve stem. A thicker shim will raise the bucket in relation to
the valve stem, therefore reducing the gap between the surface of the
bucket and the cam lobe. A thinner shim will increase the gap. This
is purported to be a very stable adjustment system.
To adjust the valves, first measure and record the existing clearances.
Next, check the manual for the reommended clearances and note those
as well. (I do this on paper in columns for each valve.) Do the math
to come up with a delta value for each valve. Pull the cam according
to the manual. Remove each bucket and shim and keep them in order.
Use a mic and measure each shim thickness in turn and record the values.
Do the math again by adding the delta value (either plus or minus) to
come up with the new shim thicknesses. Order new shims as required.
When reassembling, make sure the buckets go back on the same valves.
Keep your old shims and mark their thicknesses with a permanent marker.
When I did mine I think I had to order four shims.
The only hassle with this system in my eyes is that you have to order
the shims which I can get in a day or so from Moss. I'm used to not
having to order parts (save a cam cover gasket) for a valve adjust.
Hope this helps.
Cheers,
Kurt Oblinger
Redondo Bch. Ca.
'80 TR7 Spider FI
and other TRs
c394829@is6.mdc.com
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