Dick:| |> But why the mystery? .020 is a visually noticeable difference.
|
Bob: | I suppose it is. It's just that 2/100 of inch does not seem like it
| would be a easily noticed difference.
Dick: If you lay the two pistons on their sides on a flat table, head to head
you should have no trouble seeing a .020 (1/2 mm) step. It is bigger then
your ignition point gap. Almost as big as your spark plug gap.
Bob: | ............................ in my garage
| (though with the mess out there anything is possible :-)
Dick: Mine too. New life forms may be developing in the primordal oooz.
Bob: | I bought a vernier caliper and measured the piston and the bore.
| Everything looks okay.
Dick: Great!
Bob: | I think the piston rings I've got are okay, although I'm pretty sure I
| need different rod bearings, as there is a "020 u/s" on the back of
| the ones I took out :-( Strangely, the crank journals measured stock
| with the vernier caliper, confusing me yet again. Got any simple ways
| to check this out?
|
Dick:
yes: the bearing hole in your engine block or piston rod is a standard size
so the OUTSIDE diameter of the bearings shell is always the same. If the
journal
is .020 undersize, the INSIDE diameter of the bearings shell is .020 diameter
smaller (or .010 radius smaller) so the bearing shell is .010 thicker then the
stock bearing shell. Use your new calipers to check.
Also when assembling the crank in the block use "plasi-gage" to be sure
your clearances are right. Assemble the new crank bearings and crank in the
block
dry with about an inch of plastigage across the width of the journal. Then
torque the bearing bolts to spec. Disassemble the bearings and compare the
squished plastigage to the example measurements that come on the PlastiGage
package.
The tighter the clearance the wider it squishes out. Assuming it measures
right,
use some WD-40 or kerosene to carefully wipe away the reminants of the
plastigage.
Lube the bearings with assembly lube (I like REDLINE assembly lube, though I
used
to use a finger full of STP) Reassemble and retorque the bearings. Just before
starting the engine prime the oil system(pump, filter, gallerys etc.)
PlastiGage costs about $2 a stick. Your clearance is probably about ~.002 to
~.003
so get the middle size plastigage(I think). When I have skipped this step I
have
some times regreted it.....
| |> good luck
|
| |> dickn
|