Les Myer wrote:
> a press and a special piston fixture is usually used - this is called
> pressing the piston pins out and in.
That's what I figured.
> >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.
Bob Hoover explains how to build a simple wrist-pin puller or pusher at
http://www.type2.com/sermons/liturgy/pistonpins.html
He is covering a VW Type II engine, but the concept is the same and this
simple tool if carefully constructed could certainly do the job. I was
confused about using temperature to do wrist pins. Bob explains how to
put new valve guides in a VW head with this method at
http://www.type2.com/sermons/liturgy/headjob.html
Look for the "Replacing the Valve Guides" heading.
> 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.
Ahh.. thanks again. This issue and line boring had both been black boxes
until now. Makes perfect sense. Are the rods measured first to
determine if they are out-of-round, or just generally sized as a matter
of course?
> 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.
I intend to use a ring expander.
I want to build a good engine, but I can't afford to do it 110%.
Instead, I want to build a reasonably durable engine. My goal is to get
60k from this engine (it is not tuned in any way) and along the way build
a more performance-oriented engine with maximal care. When this engine
wears out (or impatience gets the best of me), I will make the swap.
I am having the crank magnaflux'd and ground (if it needs it). The head
is already new last year. I intend to replace the rod bolts as
insurance. I'm replacing the oil pump and timing gears/chain because I'm
in there and they were on sale.
--
Matt Liggett
'60 Mini, '70 Midget, '89 SAAB 900t SPG
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