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VN1700 pistons, in a 1600

608 Views 2 Replies 3 Participants Last post by  Bongopony
I may be shooting at the moon here, but I bought a pair of VN1700 pistons/con-rods from a salvaged VN1700 with only 11,000 miles on it. The 1600 and 1700 share the same cylinder bore size. But the stroke is longer on the 1700, plus the crank journal swing on the 1700 is probably greater than on the 1600. I have to tear down my 1600 to fix the 2nd gear issue, so I'll be into it deep enough to do all sorts of internal mods. I doubt the conrods will be the same length and journal sizes for the 1600 and 1700, so I plan to only use the 1700 pistons and not the con rods in my 1600.

I already have VN1500 Mean Streak heads (bigger valves), cams (hotter, more lift), throttle body/injectors (bigger bore) a Mean Streak gearset (2nd, 3rd and 4th are lower ratio than the Classic) but I'm keeping the Classic 5th gear for highway speeds. So, IF the pistons from the 1700 have the same piston pin diameter, and IF the distance from the wrist pin centerline to the piston deck is only slightly higher than the 1600 pistons, I should be able to use the 1700 pistons and bump the compression ratio up slightly along with all the other mods to get more oomph. I'm not changing the stroke (like a stroker crank in a Chevy V8), just changing the pistons for a slightly higher compression ratio.

I will probably have to assemble the jugs/heads with the 1700 pistons in it, and then use modelling clay on top of the pistons to turn the engine over by hand to check for piston to valves clearance. The 1700 pistons are more flat on top than the 1600 (which are dished down slightly), and the 1700 pistons do have valve clearance recesses machined onto the piston crown. If the clearance proves out I can run the pistons as is. If the clearance is too close I may make some thicker base gaskets to just slightly raise the deck height of the heads.
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