wezze93
Expert Class
Posts: 127
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posted February 04, 2004 09:20 PM
86mm piston
what is a 86mm piston is it a 1270 or 1287 an will it hold up to NOS
   
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cowboy
Pro
Posts: 1061
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posted February 04, 2004 09:22 PM
1287 and if it will hold up to nos depends on alot of other factors
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ninja12
Needs a job
Posts: 3310
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posted February 06, 2004 02:14 PM
1270 vs 1272
1287 vs 1290
Is this marketing
or different calculations for the same bore stroke
or actually different
Muzzy claims 2.5mm increase over the 83mm stock bore in the1270 ad , but 85.4mm on the billit crank ad. Which is true?
Wiseco 1272 claims 85.5 mm
Does it matter .1mm = .00394 of and inch or 3 cc spread over 4 pistons.
Are the build tolerances that tight from either of these companies?
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted February 06, 2004 03:28 PM
 Edited By: dougmeyer on 6 Feb 2004 15:29
ninja12,
The actual bore diameter on the Muzzy "1270" kit is 85.4 mm, which yields a displacement of 1269.33 cc's. The 85.5 cc cited is a rounded figure which, if used, would as you correctly point out, yield a displacement of 1272 cc's.
Again as you correctly note, the difference is little more than the actual piston/bore clearance. In any case, the bore will vary based on what clearance the builder chooses. When we do a kit, the pistons are individually measured and the final bore size (and displacement) is determined by the actual piston diameter plus the recommended clearance.
And yes, the tolerances are that tightly controlled.
Doug
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