Connecting Rods 3.2 vs 964

[rothaus]

Good morning, I have a set of connecting rods that came from a 964, and want to use them in my 3.2 1984 engine.

I measured them and noticed that there is a difference in thickness at the big end.

1984 - 1985 = 21.70 - 21.80mm
1986 - 1989 = 21.85 - 21.90mm

The 964 I got measure between 21.873 - 21.890mm which is within specs as for the 1986 - 89. All other dimensions are all withing specs.

Why are the later con rods are thicker by 0.1mm ? and can they used as is with the 1984 crankshaft ?

Thanks for any input on that.
Engelbert

[gled49]

Check the center to center measurements as rods are for different strokes.

[rothaus]

Originally Posted by gled49

Check the center to center measurements as rods are for different strokes.

There are both 127mm 3.2 as well 964 3.6

However, I found that the part number for the 3.2 1984 - 86 is 930 103 020 XX

The Part number for the 3.2 87 - 89 and 964 3.6 is 964 103 020 XX

XX for the weight group.

So here again, it looks like the later con rods for 3.2 and 3.6 are 0.1mm thicker at the bid end, but why ? And can these used for a 1984 crankshaft.

Thanks
Engelbert

[rothaus]

What I found is that the clearance rod/side wall is different for 78 - 85 and 86 - 89, source is Wayne's book.

78 - 85 is +0.200 - +0.350
86 - 89 is +0.100 - +0.200

That would mean the crankshaft is the same for all 3.2, but the clearance was reduced, and therefore the rod at the bearing end is 0.1mm thicker.

So I can use them in my 84 Engine as is.

Engelbert

[PeteKz]

Test assemble one on the crank. As long as it turns freely and has, say, 0.1mm of clearance, you should be good.

[rothaus]

Originally Posted by PeteKz

Test assemble one on the crank. As long as it turns freely and has, say, 0.1mm of clearance, you should be good.

Thanks, I will do that as soon the crankshaft is back from repair.

Thanks
Engelbert