offset grinding crank
#1127203
12/04/11 02:05 PM
12/04/11 02:05 PM
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Joined: Aug 2009
Posts: 113
utah
jjl
OP
member
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OP
member
Joined: Aug 2009
Posts: 113
utah
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I have a late model 440,and we all know the pistons are down in the hole a long way.How much do you offset grind the rod journals to get as close as possible to zero deck?Can it be ground that much?And still use the stock rods.Looking for an inexpensive way stroking and comp. increase.If they were .100 in the hole do you grind it .100 or .050.How does that work.
formally orangemonster
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Re: offset grinding crank
[Re: jjl]
#1127205
12/04/11 02:41 PM
12/04/11 02:41 PM
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Joined: Aug 2003
Posts: 43,237
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,237
Bend,OR USA
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Quote:
I have a late model 440,and we all know the pistons are down in the hole a long way.How much do you offset grind the rod journals to get as close as possible to zero deck?Can it be ground that much?And still use the stock rods.Looking for an inexpensive way stroking and comp. increase.If they were .100 in the hole do you grind it .100 or .050.How does that work.
There is no inexpensive way to increase the stroke and compression   I have had several crankshafts offset ground to increase the stroke, that ends up using BB Chevy rods on the BB 440 cranks and SB Chevy rods on the offset ground SB Mopar cranks. That use to be the cheapest way to increase stroke and compression using a custm made pistons, there never cheap  Do you have access to a good crankshaft grinding company? If so ask them how much to offset grind your rod journals to 2.200 size and make the stroke 3.91 or 3.90. That is the BB Chevy rod journal size, I have built several 440 motors with that combination, I used a set of 4340 BB Chevy type H beam rods rods that are 7.100 long center to center and a set of KB forged shelf pistons made for that combination   Not really cheap but a little bit cheaper than most larger stroker kits BTW, depending on the bore size you can end up with 460 to 471 C.I.  The last one of those type motors that I built for bracket racing with high compression(12.8 to 1) pistons and all race parts made 720 HP at 7000 RPM 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: offset grinding crank
[Re: jjl]
#1127208
12/04/11 03:13 PM
12/04/11 03:13 PM
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Joined: Aug 2003
Posts: 43,237
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,237
Bend,OR USA
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One of the NHRA Stock and Super Stock engine building blueprint tricks is to take a standard crank and offset grind it to .014 or .015 increased stroke, use the stock type rod and appropriate rod bearing sizes to increse the stroke the max. allowed by NHRA rules. Not worth doing on a street motr unless you really want the last tiny bit of performance for your motor. Buy a set of pistons to increase the compression :twocents
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: offset grinding crank
[Re: jjl]
#1127209
12/04/11 03:15 PM
12/04/11 03:15 PM
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Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
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I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
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If you turn a good crank down .030 you can do all .030 aditional stroke at the same timme and that only pushes the piston up .015. You will get very few cubes and very minimal increase in compression. All told you will be real lucky to get 10 hp from that.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: offset grinding crank
[Re: Cab_Burge]
#1127210
12/04/11 03:17 PM
12/04/11 03:17 PM
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Joined: Nov 2003
Posts: 6,293
Rock Springs
Bob_Coomer
master
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master
Joined: Nov 2003
Posts: 6,293
Rock Springs
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It can be done, but why spend several hundred dollars to offset grind a crank and only gain .010-.020 in compression height or stroke?
It might be worth .1 in compression ratio.. You would probably gain more power by removing the air cleaner...
No joking
[color:"red"]65 Hemi Belvedere coming soon [/color]
[color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]
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Re: offset grinding crank
[Re: jjl]
#1127212
12/05/11 11:51 PM
12/05/11 11:51 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
small,hp gain,small comp gain,small torque gain.Almost compensate for the thicker head gasket.
Well this answered a few questions,specifically gaining only half of what is offset in comp height.Thanks guys. 
As stated you can offset grind for .030 bearings with a Good crank if you can find a shop skilled enough to do it and not lose the outer peak. But that will be some bucs! $$$
What will you gain?
From a 3.75 crank you will gain stroke to 3.765
With a 4.32 bore that will give you a 1.76 ci increase! On a 500HP motor that might be good for 2 HP. 500 HP divided by 440 ci = 1.136 hp per ci. 1.76 x 1.136 = 1.999  
Further with a stock Eddy 84 cc head the comp will jump from 8.7 to 8.731
With pistons in the hole .100, a better route would be to shave the heads.
As a example, if you had the stock 84 cc Eddys and shaved them .050 to 74 cc. The comp increase would be from 8.7 to 9.45
On a Same said 500HP motor as before you would see about a 5% increase in HP , or around 25 HP
The cheaper cost to shave a head .050 is Waaaaay better and HP productive then to offset stroke a crank for a .015 gain in deck height from a piston being .100 in the hole to .085 in the hole. 
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. Tim