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Old 09-25-2014, 08:55 AM   #1
Johnnydidd
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Default How do you tell the dfferance in cranks

My brother has flathead crank says comes out of Mercury, anyway to tell if its 4 inch stroke, thanks John
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Old 09-25-2014, 09:00 AM   #2
Binx
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Default Re: How do you tell the dfferance in cranks

Here you go...

http://www.flatheadv8.org/boomer/crank.htm
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Old 09-25-2014, 09:00 AM   #3
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Default Re: How do you tell the dfferance in cranks

http://www.flatheadv8.org/boomer/crank.htm

R
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Old 09-25-2014, 01:37 PM   #4
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Default Re: How do you tell the dfferance in cranks

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Thanks for the reference, as very useful !
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Old 09-25-2014, 04:23 PM   #5
Johnnydidd
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Default Re: How do you tell the dfferance in cranks

Very easy to use thaks alot, john
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Old 09-25-2014, 07:40 PM   #6
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Default Re: How do you tell the dfferance in cranks

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I didn't read the above references, so please forgive if this is redundant.
I simply support a couple of the mains on 2x6's or 2x8's, and roll the crank a half turn, and measure the stroke. Simple, direct, and I don't have to depend on 5/8 clean-out plugs and the like. JMO
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Old 09-25-2014, 07:55 PM   #7
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Default Re: How do you tell the dfferance in cranks

So it's just the later model mercs that have the larger crank?
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Old 09-25-2014, 08:05 PM   #8
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Default Re: How do you tell the dfferance in cranks

49 to 53 in USA and 49 to 54 in Canada
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Old 09-25-2014, 08:45 PM   #9
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Default Re: How do you tell the dfferance in cranks

I'm going to be getting two 41 mercury motors from a guy. I know from looking at van pelts they make more horse power. Is it just from larger bore. And higher compression heads?
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Old 09-25-2014, 09:25 PM   #10
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Default Re: How do you tell the dfferance in cranks

Larger bore.
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Old 09-25-2014, 09:33 PM   #11
Mike B
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Default Re: How do you tell the dfferance in cranks

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Larger bore.
The bore is larger?...thought the CI's came from the extra stroke?
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Old 09-25-2014, 09:39 PM   #12
bart78
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Default Re: How do you tell the dfferance in cranks

Van Pelts shows 3.75 stroke. And 3.1875 bore for the 41. The guy was telling me the crank was bigger. I knew some of the mercs were.
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Old 09-25-2014, 11:23 PM   #13
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Default Re: How do you tell the dfferance in cranks

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The bore is larger?...thought the CI's came from the extra stroke?
41 Merc is 3 3/16" bore x 3 3/4" stroke = 239 cu in.


41 Ford is 3 1/16" bore x 3 3/4" stroke = 221 cu in.


49-53 Merc is 3 3/16" bore x 4" stroke = 256 cu in.


49-53 Ford is the same bore and stroke as the 41 Merc


42-48 Ford and Merc were the same bore and stroke 3 3/16" x 3 3/4"= 239 cu in.

Bill
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Old 09-25-2014, 11:37 PM   #14
Mike B
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Default Re: How do you tell the dfferance in cranks

I see what you were getting at...I thought you were saying Mercs had a larger bore than a 239 Ford...didn't realize you were bring the 221's into the mix.
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Old 09-26-2014, 01:13 AM   #15
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Default Re: How do you tell the dfferance in cranks

Is there a difference between the Canadian and USA merc engines in 1949?
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Old 09-26-2014, 10:02 AM   #16
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Default Re: How do you tell the dfferance in cranks

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Originally Posted by bart78 View Post
Van Pelts shows 3.75 stroke. And 3.1875 bore for the 41. The guy was telling me the crank was bigger. I knew some of the mercs were.
Pre war 239s (99 block) started the larger rod journal ( 2.139") vs 2" on 221s

That 99 block is identified as having a round center water transfer port in
the deck . Later blocks had round middle and lower ports

Gene Tulsa
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Old 09-26-2014, 11:04 AM   #17
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Default Re: How do you tell the dfferance in cranks

Just to clarify, Ford Canada used the CEAC 4" stroke flathead in the '53 Mercury and Monarch, '53 and '54 Meteor (except base model) and '54 Fords (except base model). '54 Mercury and Monarch had the 256 OHV. And no 6 cylinder Fords until '56. ..B.
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Old 09-26-2014, 08:20 PM   #18
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Default Re: How do you tell the dfferance in cranks

To increase power, there is no substitute for increasing displacement. Increasing stroke is the usual method. Overboring a flathead block often results in ruining it due to sand holes or thin cylinder walls. Over the years, there were lots of claims of having a "Merc crank", but more often it is for bragging rights, or to sell a car. Only pulling a head and measuring is proof, unless the crank is out of the engine.
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