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I was sort of casually looking around at other rod applications that might work and not having any success. I measured the big end width on mine as 1.25 inches (31.75mm), and I have yet to find any rods that are that wide. I guess that's a pretty generous helping of bearing surface for a rod. I guess it would take either some custom rods (which I could make work with just about *any* 92mm piston I wanted) or some stock rods and B21 pistons - and get the 6 bolts writ pin holes bored for an interference fit on the 8 bolt wrist pins.
Or perhaps an 8 bolt crank has more mainstream measurements? Anyone know what the big end bore and width is on an 8-bolt rod? I can't seem to find specs like these for old Volvo engines anywhere.
Mesurements (in inches) I took on my 6-bolt parts:
Con rod:
Big end bore - 2.28
Big end width - 1.25
Center to center length - 5.72 (4.15 edge to edge plus 1/2 big end bore and 1/2 pin bore)
Pin end width - 1.20
Pin bore - .86
Piston:
Bore diameter - 3.62
Pin diameter - .86
Compression height - 1.83 (1.40 edge to top plus 1/2 pin bore)
Overall height of both - 7.55 (Rod center to center + piston compression height)
Practically all pistons I see have a lower compression height than 1.83 - most are in the 1.3 - 1.4 ish range. I'm still pondering the thought of getting some pistons like that and having some custom rods made that are longer too compensate. Some of the discussion I've seen regarding rod lengths seems to indicate that a longer rod is somewhat better for higher rpm use as the piston remains at (or near) TDC and BDC slightly longer as opposed to a shorter rod (same crank throw). In addition the peak acceleration on the piston goes down as the rod gets longer, theoretically making it handle higher rpms better. The stock rod to stroke ratio is ~1.81:1, adding another .4 inches to that gives a ration of ~1.94:1 - which seems fairly close to the top of generally accepted range of 1.5 to 2:1.
But, all in all, the price factor will probably end up steering me down the simpler and cheaper path of the B21 pistons and stock rods.
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I'm JohnMc, and I approved this message.
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