Well here is another Bob to try to answer some of your questions.
>
> Hi Bob,
> I am pretty certain that the piston went in from the bottom at the
> factory,
Yes, no other way to do it.
probably pre-connected to the rod.
MUST be pre-connected to the rod, upper pinch bolt must be torqued to 33 to
34 ft-lbs or the top bolt will stretch and you have a danger of rod
breaking at the top. Never hold the rod while torquing the pinch bolt as
you will bend the rod. Hold the wrist pin, two buttons in the wrist pin
holes and a vice are required before you torque the pinch bolt.
But, with the crankshaft in
> place you're going to have a very difficult time getting a ring
> compressor in there and getting the piston to enter the cylinder.
You can fit the rings with a jubilee hose clamp or your fingers, not easy,
but possible.
I gave
> up on the challenge, removed the piston from the rod and pushed piston in
> from the top.
OK, but how did you connect the rod and tighten the upper rod bolt?
In the original casting, there was probably some
> chamfering that made piston insertion easier. Once an engine is bored,
> though, that chamfer is gone.
Agreed, the chamfer is gone at about +0.060" bore.
> Somewhere I read that rods being in backward is a bad thing, and an
> explanation for it. Of course, I forget where any why, but a dim memory
> tells me that it had to do with the oil squirting out of the drillings
> and lubricating wrist pin or piston or cylinder wall....
Cylinder walls need to be lubricated on the trust face of the piston, this
is away from the camshaft, same side as the pinch bolt.
> I would turn them around.
I agree, turn the pistons/rods around so they are inserted correctly.
That, of course, brings up the further
> problem that you may not know if the front of the piston is facing the
> front of the engine.
Check it out and correct the problem.
> > As several list members advised, I was able to remove the piston and
> > rod from
> > the bottom past the crank. I found this had to be done on the
> > camshaft side
> > of the engine and it's a bit tricky. The crank rotation, piston and
> > rod all
> > had to be manipulated in order to "sneak" the assembly out.
Goes in the same way.
Once out
> > I could
> > not get a socket to go over the wrist pin clamp bolt because it's so
> > close to
> > the rod. Horst Schach in The Complete MG TD Restoration Manual
> > suggest using
> > an open end wrench, but my wrench couldn't get a good enough grip on
> > the bolt
> > and it started to round off the head. So next I tried grinding down
> > the
> > outside diameter of my 1/4 W socket as far as possible, but it still
> > wouldn't
> > fit.
I use a 13 mm socket and grind through one side on an angle till it fits
over the pinch bolt head. You need to tap the socket on and it works.
I then used the flat side of my Dremel cutting wheel to grind
> > down the
> > ridge on the rod adjacent to the bolt head.
This was a very dumb thing to do. The rods are already suspect in the pinch
bolt area, you have just made them worse.
This provided just
> > enough
> > clearance for my modified socket to fit over the bolt head. This did
> > the
> > trick and I don't believe I removed enough metal to cause any
> > balance problems (I hope).
No not balance problems , but what about rod stress risers and strength?? I
can't believe you did this!
BTW, in future, a much better rod bolt is a high strength socket head cap
screw, 8.0 x 1.0 x 30 mm long. Piece of cake to now get an Allen wrench on
the pinch bolt and torque to 33 to 34 ft-lbs.
> >
> > Now does the new piston go in from the top or the bottom?
Bottom, tighten rod bolt in a vice first.
I can
> > envision the
> > piston going in from the top and pushed down just far enough to
> > allow the rod
> > and wrist pin to be attached from the bottom. Now that I can get my
> > socket on
> > the pinch bolt, I could tighten it with an extension.
Never work.
Or should the
> > rod and
> > piston be assembled and then installed from the bottom the same way
> > they came
> > out? If done from the bottom, can you get a ring compressor in there
> > past the crank?
Probably not, I have used a jubilee hose clamp.
If not, can one compress the rings with ones hands?
Yes, it will work.
> >
> > By the way, the shop manual seems adamant about the rods being
> > assembled with
> > the pinch bolts on the right hand side of the engine. Naturally the
> > DPO had
> > them in the other way. Should I turn all the connecting rods around
> > the right
> > way or leave them alone?
I would change them, oil goes through the squirt hole in the rod to
lubricate the bore thrust faces.
> >
> > Thanks for all the advise. You should see how badly the old piston
> > is beat
> > up. No matter how I get the new piston in, it's got to be a big
> > improvement.
Well maybe, but not if you proceed with inserting the piston from the top
and installing the rod from the bottom. Guarantee if you do not torque the
pinch bolt you will have a rod problem. That could lead to BIG expensive
noises.
Regards, Bob Grunau
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