The machinist will have to install the pistons on the rods
>
>The wrist pins are an interference fit in the rods and fit close in the
>pistons. Correct?
on a 1275, yes.
>
>What tools will the machinist use to do this?
a press and a special piston fixture is usually used - this is called
pressing the piston pins out and in.
>
>I have been told it is doable by heating the pistons and rods to about
>450degF and chilling the wrist pins in the freezer overnight.
>
Could work - I have never seen published instructions on doing this. Plus
the pins need to be put the small rod end to a certain depth. Sounds like
a pain to me. What if the first try doesn't work and the pin doesn't go in
all the way before it warms up and catches - then what?
>> (which will probably need resized on the big end anyways)
>
>What does it mean to have the big ends resized?
The rod bearing bores are re-sized to ensure perfect roundness and size as
well as the angle to the piston pin (if the angle is very bad, the rod is
considered "bent" and is discarded. This is done by machining a small
amount of material off the rod cap mating surface, making the bores ever so
slightly egg-shaped and a little smaller. Then the hole is restored to
specifications with a hone to sub-thousandths accuracy (remember oil
clearance typically runs 0.001 to 0.002.) This is also basically how line
boring is performed, only on the main bearing seats.
>
>> When going back together, remember the longer rod-cap boss on rods 1
>> and 3 goes to the rear - on 2 and 4, the long boss goes to the front.
>
>Thanks.
>
>> If the piston has a dot or a mark, this goes to the front (otherwise
>> they are probably omnidirectional pistons). If this is your first
>> time, it might be best to have an experienced friend show you how to
>> orient the rings (yes, you need a special tool to get them on the
>> pistons without damaging them or the pistons), compress them, install
>> the crank/pistons/bearings, and how to plastiguage clearances.
>
>I plan to get some guidance, but all of my car friends live a few hundred
>miles away, so the best guidance I'll get is by telephone or e-mail.
>
>> Not meaning to scare you, just trying to save some heartache and
>> frustration as well as make sure it is done right.
>
>I appreciate it. This is the sort of guidance I'm looking for. But, I
>am on a budget and I am determined to understand every part of the
>process, even if I farm it out to a machinist. I also intend to do as
>much as I can myself. Guess I've been reading a little too much Bob
>Hoover, eh? (See http://www.type2.com/sermons/).
>--
> Matt Liggett
> '60 Mini, '70 Midget, '89 SAAB 900t SPG
>
Next, someone will tell you that you don't need a ring expander to get the
rings on the pistons. True, you don't if you don't mind scratching your
new pistons with the ring gap ends and improperly stressing the rings.
What can I say, I'm pretty anal when it comes to engine building.
Good luck, have fun -
Les
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