..
The message from the Imp owner about how he installed .010 o/s rings
by filing down the gaps, is another example of emergency engineering
which is born of poverty and/or lack of proper parts. The oversize
rings could not form a proper perfect circle fit into the cylinders
but he was satisfied with the results and likely the rings did
eventually wear into an improved fit.
You may NOT intend to beat on this spare engine but you do expect it
to run quiet, no smoke, and normal compression etc. None of these
criteria will be obtained with loose clearences.
What is needed is one of two things:
Either bore up to the next std o/s which I assume is .010 o/s in your
case. Then fit that size pistons and rings !
Or..... First determine if there is ANY RIDGE at the top of cylinder
and if yes, then use a ridge reamer to cut that tiny ridge off and
thereby obtain a STRAIGHT un-ridged cylinder wall. This is important
to keeping the hone stones completely in wall contact and prevent the
stones riding on a top ridge. Next use a hone which is a long size
stone hone . Some are short stones and don't bear well and true. Also
make certain the stone grit is not too severe and will leave a fine
smooth final finish, not a coarse finish.
Next wash cylinder walls with diesel fuel or kerosine (not mineral
spirits....we want some oiliness affect).
Insert hone and using a slow rpm 1/2" drill, start the hone while
moving up/down slowly so as to create a cross hatch affect in which
the up/down markings cross one another at 30 to 45 degree angles.
On the up stroke have your stones clear the top of the cyl by about
1/2-3/4" and about the same at the bottom of the cyl (don't crash
stones into any part of crankshaft).
Stop every 30 seconds and squirt more lube into cyl. and regularly
remove the hone and wash off the stones. When removing hone, first
squeeze stones together so as NOT to mark the cylinder wall with a
vertical drag line.
Keep this up until you have removed 100% of all raised rusted
portions and have an even surface of polished affect from top to
bottom.
When you decide the work is all done, the block MUST be properly
washed to remove grit from the stones. Use common hot water and soap
to scrub out all cylinders . When done, apply a coat of motor oil to
prevent rusting of the clean walls.
What is left is the pits which will of course be BELOW wall level.
While they are not nice and look like hell, in actuality, they serve
as oil traps and help lube piston and rings . We can accept pitted
walls if the condition is below the top two ring positions (reason
being that at the moment of power explosion, the two compression
rings are jammed hard against the walls and we would like to have a
nice clean fit in that area).
You will NOT be able to remove a great amount of metal with the hone
and after about 3-5 minutes in a single cylinder you will have it
perhaps .002-.004" oversized if even that much !
Now then, this sort of a cylinder can be fitted with a STANDARD
piston and ring set and will usually break in nicely and give nice
long service. Make certain to use ONLY a U-Flex oil ring set. This
is the ring which is actually a stampped spring steel and looks like
a letter U with the open part against the cyl wall. It is the very
best of oil control rings ever invented and due to the pitted
cylinder surfaces you will have it is the best type to use.
However.......before ending this advice I must caution that what you
have done is not a first class engine job. As you already know,
there is lots more to "rebuilding" than what is discussed here and a
proper rebuilt engine will have had line bored mains, rebuilt con
rods, new cam bearings, cyinders bored while block is aligned on main
bearing saddles, cautic soda degreasing of block, new core plugs, oil
pump possibly changed or at least end play adjusted, crank thrust
washers adjusted, etc. etc. etc.
I purchased lots of new bare engine blocks from Rootes and used them
in customers rebuilds but I would point out that a used block has
been "stress relieved" over the years and we always used only a used
block for race engines. In this way our machine shop tolerences were
better retained when the engine was heated up. In fact, my personal
race engine blocks were heated in a stove we made from 55 gal oil
drums and fired by drain oil. Once the block was up to about 200-250
deg F. we dragged it onto the boring machine and set it up as fast as
possible , wrapped in old blankets to hold the heat, and then bored
cylinders. When it cooled too much it went back to the oven for a re
heat as necessary.
Once the machine bed was set properly this was a quick operation of
on/off the machine.
This sort of fussy perfection is of course NOT required for normal
engine jobs.
Dick T.
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 10:02:28 CDT