Re: Can a 4" stroke SB crank be turned to?
[Re: rt66jim]
#2285406
04/10/17 06:49 PM
04/10/17 06:49 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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You'll get maybe .125 if you can take it that far.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Can a 4" stroke SB crank be turned to?
[Re: justinp61]
#2285432
04/10/17 07:47 PM
04/10/17 07:47 PM
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Joined: Jan 2003
Posts: 4,002 Joplin, Mo
rt66jim
OP
master
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OP
master
Joined: Jan 2003
Posts: 4,002
Joplin, Mo
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4.25" cranks are readily available. I know but I have a set of Pankle rods with the smaller journal. I would like to use by just turning the crank I have.
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Re: Can a 4" stroke SB crank be turned to?
[Re: rt66jim]
#2285435
04/10/17 07:52 PM
04/10/17 07:52 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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4.25" cranks are readily available. I know but I have a set of Pankle rods with the smaller journal. I would like to use by just turning the crank I have. You can.. just talk with your crank grinder for the clearance needed.. smaller dia will use less
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Re: Can a 4" stroke SB crank be turned to?
[Re: MR_P_BODY]
#2285447
04/10/17 08:11 PM
04/10/17 08:11 PM
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Joined: Jan 2003
Posts: 1,784 PA
W5DART66
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,784
PA
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2.125"? Or 2.100"? So 2.125" down to 1.850" = .275" you can not get it all but .250" should clean up back to round. So your stroke gain would be .500". 4.500" stroke but 1.85 on 4" crank will have no Journal overlap. Anything you offset will be 2 times the stroke gain. So .050" offset will give you .100" gain in stroke.
Last edited by W5DART66; 04/10/17 08:12 PM.
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Re: Can a 4" stroke SB crank be turned to?
[Re: MR_P_BODY]
#2285449
04/10/17 08:21 PM
04/10/17 08:21 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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Those NASCAR rods are the siren luring you onto the rocks. The Honda journal, though, is 1.889" The Mitsubishi journal is 1.850"
Hughes' stroker was such an animal, a few years ago, except it used the Honda journal. 4.180 stroke.
R.
Last edited by dogdays; 04/10/17 08:22 PM.
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Re: Can a 4" stroke SB crank be turned to?
[Re: Blucuda413]
#2285457
04/10/17 08:29 PM
04/10/17 08:29 PM
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Joined: Dec 2013
Posts: 403 Romulus, MI
GTS340
mopar
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mopar
Joined: Dec 2013
Posts: 403
Romulus, MI
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Man, I wish mine would have worked like that. When I did my crank from a 2.125 to 2.00 I only gained .125 and only ended up with a 3.91 stroke What did I do wrong?? Did nothing wrong! Lots of WRONG info in this thread. Change in journal size is the max you can gain by offset grinding! 2.125-1.850=.275 MAX added stroke theoretically .250 is realistic
Last edited by GTS340; 04/10/17 08:29 PM.
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Re: Can a 4" stroke SB crank be turned to?
[Re: GTS340]
#2285530
04/10/17 10:04 PM
04/10/17 10:04 PM
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Joined: Jan 2003
Posts: 1,784 PA
W5DART66
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,784
PA
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Man, I wish mine would have worked like that. When I did my crank from a 2.125 to 2.00 I only gained .125 and only ended up with a 3.91 stroke What did I do wrong?? Did nothing wrong! Lots of WRONG info in this thread. Change in journal size is the max you can gain by offset grinding! 2.125-1.850=.275 MAX added stroke theoretically .250 is realistic Dude you should check your facts.... Will not argue with you I offset cranks all the time. You double What you offset period
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Re: Can a 4" stroke SB crank be turned to?
[Re: W5DART66]
#2285568
04/10/17 11:02 PM
04/10/17 11:02 PM
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Joined: Jan 2003
Posts: 1,784 PA
W5DART66
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,784
PA
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Re: Can a 4" stroke SB crank be turned to?
[Re: Blucuda413]
#2285569
04/10/17 11:04 PM
04/10/17 11:04 PM
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Joined: Jan 2003
Posts: 1,784 PA
W5DART66
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,784
PA
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Yes I know, I was just trying to throw a little levity into the discussion. The offset = stroke increase was the way it worked when I took plane geometry 70 years ago. It changes the center line of the Journal in relation to the mains. And it turns in a circle so it doubles what ever is offset ground.
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Re: Can a 4" stroke SB crank be turned to?
[Re: rt66jim]
#2285579
04/10/17 11:32 PM
04/10/17 11:32 PM
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Joined: Oct 2007
Posts: 3,978 Hilltown Pa
1967dartgt
master
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master
Joined: Oct 2007
Posts: 3,978
Hilltown Pa
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You sure about that Brett!! You only just offset the crank in the 981hp small block you built.
Brett Miller W9 cnc'd heads STR Chassis fabraction
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Re: Can a 4" stroke SB crank be turned to?
[Re: GTS340]
#2285643
04/11/17 01:28 AM
04/11/17 01:28 AM
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Joined: Oct 2007
Posts: 3,978 Hilltown Pa
1967dartgt
master
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master
Joined: Oct 2007
Posts: 3,978
Hilltown Pa
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Man, I wish mine would have worked like that. When I did my crank from a 2.125 to 2.00 I only gained .125 and only ended up with a 3.91 stroke What did I do wrong?? Did nothing wrong! Lots of WRONG info in this thread. Change in journal size is the max you can gain by offset grinding! 2.125-1.850=.275 MAX added stroke theoretically .250 is realistic Man lots of bad info in this thread. You have a engine builder correct you and you tell him he is wrong, wow. Wonder why so many people stopped posting in here.
Brett Miller W9 cnc'd heads STR Chassis fabraction
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Re: Can a 4" stroke SB crank be turned to?
[Re: 1967dartgt]
#2285682
04/11/17 03:47 AM
04/11/17 03:47 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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visualize a 1" circle inside a 2" circle. there is 1/2" of space vertical above it and 1/2 of space underneath it. If you moved the circle to the bottom it would move 1/2" (minus a bit for cleanup to get it back to concentric), this is the "throw" increase (1/2"). doubling that would be the stroke increase (1") cuz it would push the piston 1/2" higher at TDC and 1/2" lower at BDC then where it was before. EDIT for a slight stroke increase with all Mopar stuff to finalize quench for instance, CNC motorsports has 50 under SB rod bearings & eBay has some 40 under
Last edited by RapidRobert; 04/11/17 03:59 AM.
live every 24 hour block of time like it's your last day on earth
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Re: Can a 4" stroke SB crank be turned to?
[Re: rt66jim]
#2285695
04/11/17 05:15 AM
04/11/17 05:15 AM
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Joined: Aug 2003
Posts: 43,748 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,748
Bend,OR USA
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It depends on the crankshaft and its oil passages, I have several older forged top fuel cranks with Mopar rod journal sizes, one KB that is 4.500 stroke and according to the crankshaft shop I sent it to it can't be offset ground and destroked due to the oil passages or something else I can't remember now I sent them a another older forged Bryant 4.250 stroke top fuel crank with stock Mopar BB rod journal sizes with one spun rod bearing journal and they offset ground it down to 2.200 and 4.375 stroke with no issues Check twice before deciding
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Can a 4" stroke SB crank be turned to?
[Re: rt66jim]
#2285706
04/11/17 08:15 AM
04/11/17 08:15 AM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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Brett, no doubt you can build a great engine, and are an absolute master with cylinder heads, but you can't math.
"use it 'till it breaks, replace as needed"
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