Basic CID questions...
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Joined: Oct 2016
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From: Reno
Basic CID questions...
I have a 1983 Shovelhead Big Bore. The cylinders are 3-5/8", 0.30 over. The book says that I have a 4.25" stroke stock. The previous owner told me that it has a stroker kit. I'm assuming 1/4" but I'll check after I get the jugs back on. I'm calculating 97.6 CI (96.8 without the 030) stock and 103.3 CI stroked. Am I getting this right? That seems a little bigger than I expected.
Tourer
Joined: Jul 2014
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From: Lake Wales, Fl
Stock the stroke was 4 1/4 the bore was 3 1/2 (3.4975) = 81.6 cu in
4 1/4 stroke x 3 5/8 bore = 88 cu in
4 3/4 stroke x 3 5/8 bore = 97.8
If you look in the the timing hole there will be a S&S number if there are S&S wheels in there
Eastcoast Jim
4 1/4 stroke x 3 5/8 bore = 88 cu in
4 3/4 stroke x 3 5/8 bore = 97.8
If you look in the the timing hole there will be a S&S number if there are S&S wheels in there
Eastcoast Jim
Last edited by Eastcoast Jim; Jan 27, 2017 at 03:45 PM.
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From: Reno
I get:
3.4975 bore / 4.25" stroke = 93.4 CID
3.625 bore / 4.25" stroke = 96.8 CID
3.625 bore / 4.75" stroke = 108.2 CID
My numbers are quite different. Can someone explain why it's not just a simple cylindrical volume calculation?
Tourer
Joined: Jul 2014
Posts: 426
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From: Lake Wales, Fl
Thanks, Jim but I must be missing something.
I get:
3.4975 bore / 4.25" stroke = 93.4 CID
3.625 bore / 4.25" stroke = 96.8 CID
3.625 bore / 4.75" stroke = 108.2 CID
My numbers are quite different. Can someone explain why it's not just a simple cylindrical volume calculation?
I get:
3.4975 bore / 4.25" stroke = 93.4 CID
3.625 bore / 4.25" stroke = 96.8 CID
3.625 bore / 4.75" stroke = 108.2 CID
My numbers are quite different. Can someone explain why it's not just a simple cylindrical volume calculation?
Pi X r2 X stroke X 2 cylinders
a 74 " motor is 3 7/16 bore x 4" stroke
a factory 80" shovel is 3 1/2 bore x4 1/4 stroke
add 3 5/8 bore cyl = 88 "
Did you check the timing hole for S&S wheels? - Eastcoast Jim
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Tourer
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From: Lake Wales, Fl
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bore x bore x stroke x .7854 = (single cyl disp)
x 2 cylinders
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From: Reno
This is a little embarrassing. I was just using a geometric calculator in AutoCAD instead of actually doing math. The numbers looked reasonable so I didn't notice that I was looking at surface area of a cylinder instead of the volume. That's what I get for being lazy.
Now I get:
3-5/8" bore +0.030 / 4.25" stroke = 89.18 CID (87.73 without the 030 over)
If it's 1/4" stroker:
94.43 CID
If it's 1/2" stroker:
99.68 CID
Thanks for helping me figure out that I'm not as smart as I thought I was.
Now I get:
3-5/8" bore +0.030 / 4.25" stroke = 89.18 CID (87.73 without the 030 over)
If it's 1/4" stroker:
94.43 CID
If it's 1/2" stroker:
99.68 CID
Thanks for helping me figure out that I'm not as smart as I thought I was.
