[TR] TR "Standard" motor rebuild.

[Brian.L.Jones at gsk.com]

> and add a port-and-polish.

Be careful with that, Brian.  I've heard many times now that it's easy to
actually make things worse in that department, if you don't know exactly
what you are doing.  Polishing in particular can actually increase
resistance to flow and lead to drivability problems, because the "as cast"
surface creates a boundary layer that eases air flow, while fuel tends to
stick to the polished surface.

Randall

Indeed. I performed the combustion chamber work per Kastner's book. For 
the ports, I was guided by Uncle Jack, who shared with me the work that 
can be done reliably, without a flow bench, for most of the gain, and 
steered clear of the great deal of effort required for any subsequent 
benefit.

For inlets, you remove the two main cast-in obstructions and then leave 
the reshaped surfaces rough. This roughness aids fuel atomisation and 
creates a layer of stable air close to that surface that then eases gas 
flow through the port. For exhaust ports, the advice is to smooth the 
short side of the throat and then polish all surfaces to inhibit carbon 
buildup.

I have the early TR4 short log-like inlet manifold. Passing through this, 
gasses are required to navigate two 90 degree corners, with sharp edges 
and dead spaces. It is improved by rounding corners as much as the 
material allows, but being sure not to widen the 'bore'. One can read of 
gasket matching, or better, port matching, however Uncle Jack advised 
against this and I left the manifold ports alone. One area I did find for 
obvious improvement was the fitting of the insulating gasket to the 
carburettor. I marked the orientation of my insulating gaskets and put 
stud-diameter pegs in the carb's plate in place of the studs and then 
fitted the gaskets to the carburettors only. Both gaskets were off centre 
with respect to each carburettor. I had the same result with respect to 
the manifold, with gasket 'intruding' maybe a quarter-inch into the throat 
of the inlet. A few minutes with a dremel on the insulator removed this 
obstruction.

Brian