[TR] TR3 Engine Rebuild

Randall tr3driver at ca.rr.com
Sun Nov 16 22:58:33 MST 2008


> 1. Ten years ago I had a valve job done and remember reading 
> about differences in the either the valves or guides. What 
> are the options and recommendations when having a valve job done?

Not sure if you are talking about the change in exhaust valve stem diameter;
or the aftermarket bronze valve guides.

If the valves and guides are in good shape, I'd keep them.  But if you have
to change, my suggestion would be to go with the later 5/16" stems (same
size as the intakes); which will require a special "conversion" guide
(readily available from the usual suspects) to use in an early head.  I
would also go with cast iron guides rather than the bronze ones.  In theory
the cast iron will wear faster, but in practice they last plenty long
enough.  And the bronze ones have to be reamed oversize anyway, to prevent
differential expansion from causing the valves to hang up when hot; which
sorta negates the benefit of the slower wear.

> 2.   Since I have two heads from which to choose for the engine could
> someone advise me of what to consider in choosing which to 
> rebuild.

Personally, I'd go for the one in the best condition.  The TR3 head will
give you a little higher compression (meaning a bit more power and fuel
economy, but possibly requiring premium gasoline); but it's easy to adjust
that either way if you want.  Also a good idea IMO to follow some of the
modifications in the Competition Preparation manual, especially the part
about cutting away the sharp corners exposed to combustion.

> Are the valves and springs inter changeable between theses two heads ?

The only difference in valves might be the exhaust stem diameter, as above.
I say "might" because your TR3 head may have already been serviced with the
later valves, and I'm not sure if your TR4 head would have them as original
or not.

The springs interchange as long as you keep the matching shims with them.
However, most likely you will want to replace them anyway.  At least have
them tested for seat pressure.

> 2. Among my collection of parts I noticed pistons with three 
> rings and some with  four rings, one oil ring being below the 
> wrist pin. When did this change occur and what are the pros 
> and cons of each.

Beats me.  I thought the original pistons were always 3-ring.

Randall


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