Con Rod Small End Dia and Pin Spec

[deeLux]

So I looked through my Clymers book, the OEM manual, and did a quick search here and couldn't seem to find anything on it, but does anyone know the size/spec for the small end of the Con Rod and the wrist pin? The pin measures .6693", and I can't find my telescoping bore gauges to measure the rod but there seems to be a very small bit of play. Can anyone lend a calibrated opinion on this? Thanks, Chris.

[crazy steve]

For some reason there isn't a size spec furnished for the small end of the rod; Clymer says to check it and refer to 'table 1', but no spec found there....

All the FSM says is to check the pin fit and 'there should be no noticable vertical play' (page 3-25)...

The way I would read that is if you find any play and the pin isn't measurably worn (where the pin contacts the rod vs the piston), then you need a new rod.

[TomB]

The last little ends and pins I put back together had a small amount of play on the piston if you rocked it side to side in a clockwise and anticlockwise motion looking at the front of the engine (not sliding side to side which there'll be loads of play)

BUT holding the piston quite tightly I couldn't feel any play UP and DOWN..... Vertical play that Steve mentions

If that helps, I'd hate to see good rods being scrapped when they're perfectly servicable.

This engine is the quietest I have for mechanical noise. (Its also the engine with the copper head gasket, relevant? nope )

[79XS11F]

Try your test again with the parts fully oiled. There has to be enough clearance for oil to be present. When I rebuilt both my 78 and 79 engines there was the smallest amount of play at the rod small end to wrist pin. It was so small that it was almost undetectable and I was questioning myself about weather I was really feeling anything. When I added oil no play was detectable.
Rob

[deeLux]

Once I get a coffee into me, I'll go and check it out. The play I was feeling was the "clockwise/counterclockwise" that Tom was explaining about (couldn't figure out how to describe it at 1.00 am this morning). The actual up/down play was very hard to feel, almost undetectable, and everything is clean so I'll try it again with oil, didn't even click in that there should be a small bit for an oil film, thanks gents!
Chris.

[3Phase]

Dial indicator

deeLux, it won't tell you if there are any high spots or tapers throwing off the measurements but if you have a dial indicator and an adjustable stand you can measure the apparent play between the wrist pins, the pistons, and the connecting rods.

Fit the pins loose in the pistons, then check the play by prying gently with a wooden dowel and watch the dial indicator. Do the same with the pins and connecting rods.

[TADracer]

Hope this helps

These measurements were on a 79SF motor with about 30,000 miles. Taken by a machinist friend.

Connecting rod diameter (pin end) in inches
#1 #2 #3 #4
.6525” .65195” .65195” .6523”

Wrist pin diameter in inches
.6519” .6519” .6519” .6519”

As you can see the tolerances were .001" or less throughout.