The Mole, you got proper advice from Jarrid. I would add, that once you
select a piston of different weight than OEM, this piston should of course
be balanced against the crankshaft and all other rotating and reciprocating
parts in the usual manner.
Jarrid mentioned that you needed to have a certain data on the wrist pin
(gudgeon pin in limey talk) dia. but this is not required. The "compression
height" which as Jarrid quoted, is from wrist pin CENTER to TOP of piston
crown is of course the key thing. If you want to use a piston having this
C.H. different than stock Sunbeam, then the connecting rod big/small end
distance must be altered to suit matters. Or the crankshaft can be reground
to change stroke. This latter work is NOT recommended as it is not only
costly but risky in Rootes case. Much better to buy con rods which solve
the problem. Best thing of all....use pistons having the correct C.H.
-------------
Karl, yes your old dist was very wobbly. Reason why you now idle nice and
as well have more power is simply that the firing angles are now 90 deg
apart and each cyl is firing the same BTDC advance as the others are.
Prior, each was doing its own thing and costing HP. Some weeks back I
posted a long report on this very subject and if you have it, you might
want to re-read the info.
Jarrid also properly answere your query re. using comp test pressures to
figure the CR. As he said, wild cams test low, mild cam timing tests high.
Even assuming the testor had everything right (hot eng., open throttles and
slides, plugs out, counted strokes etc.) the resulting psi is valuable ONLY
to evaluate the cylinder conditions against one another..and against the
norms for similar cammed engines. The wet and dry cylinder tests are
quite usefull and tell a great deal to a trained mechanic.
----------
Tom Yang, the speedo drive is not below oil level but that is not the
problem. If oil is leaking around the drive unit or working up the cable
housing or any other obvious signs, this simply indicates the little seal
is bad. You can imagine that inside the gearbox oil is being thrown in a
violent manner when the engine is running or car moving. If this seal or
other seals and gaskets are shot, leaks occur. Likely the leaks are worse
when car is being driven but due to wind action the oil is driven back
under the car and the source is NOT always seen.
My suggestions about locating the source will help you.
-------------
Fisher Michael, Jarrid answered everything you need to know, incl prices.
I will add....yes cast cams are easily welded and in fact this is common in
cam shops. I would also suggest asking the shop to weld up the UNDERSIZED
lobe next to the dist. drive gear. This occurs when Rootes machined the
helical drive gear teeth. It is better to have that lobe (and all lobes) at
their normal full size.
-------------
Chuck N. ,enjoyed your little reminder about how the industry misquotes
itself (ie. General Motors). Also...another cutesy thought is regarding
internal combustion engines vs external combustion engines. Bet lots of
you guys NEVER thought about why we call a car engine internal combustion??
FIRST CAME the "external combustion" steam engine which burns fuel outside
the cylinder to make steam , which is then piped into the cylinder and
makes the pressure on the piston. Steam and gas turbines are similar,
combustion takes place outside the power generating turbine area.
Of course, gasoline and diesel piston engines do explode (burn) fuel right
in their cylinders, hence the term internal combustion engine.
Now there has always beeen polite dissagreement over the various forms of
jet engines because in some types the burning is right there in close
proximity to the "reacting" blades or turbine wheels, while in other
designs this burning is a bit remote from the reaction blades. In others,
like a pulse jet....there are no reaction blades at all. As a result, the
engineers argue about this internal vs external designation.(not that it
matters much?)
You are right though on the "motor" bit. A motor itself makes NO combustion
at all but uses some energy source to do work. Thus, an electric motor uses
electricity generated elsewhere, a wind or air- motor (windmill) uses wind
power to do work, a water motor uses moving water etc. etc. None burn fuel
in their own housings or mechanisms...their power source is external and
they are not "combustion" motors or engines.
Its fun to digress on these sorts of subjects.
------------
Dick T.
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