Subject: RE: TR6 Motor Spec. Question
>> Our group disassembled his motor last weekend and found a lot of carbon
on
>> the valves which is understandable with the oil usage.
>Is the carbon only on the combustion chamber side of the heads ? Or is it
>also underneath the head and on the exposed part of the stem ? If it's
>underneath the heads of the intake valves, then you've also got bad valve
>guides, and possibly too much oil getting to the rocker area.
No. 5 had oil on top of the piston when we removed the head so we removed
those valves.
There was a lot of carbon on the valve stem. There was a broken valve guide
seal which
I think was on the intake valve. New bronze valve guides had been installed.
The member who
removed the valves commented that they were tighter than he had expected
them to be.
I don't think that would have caused the problem but the broken valve seal
could have
certainly contributed to the problem. Can't really say at this point if the
seal was
damaged removing the valve though.
>> I seem to remember the ring gap
>> should have been 0.012 to 0.018.
>I don't have a TR6 manual handy, but even that sounds large for a stock
>motor. Usual is more like .006 - .010.
You could be right Randall, I am just going from memory.
> Talked to Ken Gilanders and
> he suggested that we should measure the piston to cylinder gap
Good idea.
> He thought that 0.006 piston to cylinder
> gap at the
> piston skirt would be optimal.
That's appropriate for a race motor, but a street motor could be a smidgeon
tighter, maybe only .004" or .005". IOW I wouldn't bother trying to fix
it, if you only measure .004".
> In looking in two motor manuals, there was a reference to a Class A and
> Class B cylinder diameter
The difference between those will be very tiny, less than .001". Basically
you can ignore the difference at this stage.
> but no specs for 0.010, 0.020 diameter
> tolerances.
>Just add .010" or .020" to the standard diameters given.
>For that kind of oil consumption, you're not looking for a .001" or even
>.002" error, it's got to be something huge. The .025" ring gaps might do
>it, but I'm guessing there's something else as well.
Maybe, we are going to measure all the cylinders and see how we match up
with
the pistons first I think. Got to start somewhere... If the valve seal was
damaged
during the original assembly and if you consider the huge ring end gap,
that could certainly be a big chunk of the problem. We might find something
else
as we get into it more. I would hope that repairing those two issues would
do
wonders for his oil milage.
Thanks,
Dave
Was this an amateur mechanic that installed the rings without checking the
gaps ? Or is there a professional somewhere we should be avoiding ?
Randall
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