3.75" Stroke Crank?
08-23-2006, 11:02 AM
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3.75" Stroke Crank? Is there somebody that makes one or is it a custom only set up? I kinda got something cookin in my lil noggin (well it's actually kinda big and prolly full of water) and a 3.75" is what I need. I looked around and haven't found one yet. Still looking though. 
08-23-2006, 12:43 PM
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SS thats kinda what I was thinking the situation is. I gotta find out if they just want my first born or if they want my nuts too.
Chuntington what I got going in my head is to basically build a 400ci with a good rod ratio 4.125" bore 3.75" stroke and a 6.2" or maybe even a 6.3" rod. I'd either use a LS7 or a L92 top end of course have it all worked over especially if I use the L92.
I kinda got a soft spot for the 400 ci number but I don't like the small bore ones that are out there (well actually I'm hung up on the 4.125" bore) you see I had an OLD ('72) 4 bolt 400ci SBC for years that I was gonna build and put into something but I got distracted by the LS1's and sold it well now I want to put a 400 in the X. It's gonna be a DD and I want to keep it to where I feel it's gonna be durable ie. why I'm concerned about the rod ratio.
Really I'm just kicking the idea around.
Chuntington what I got going in my head is to basically build a 400ci with a good rod ratio 4.125" bore 3.75" stroke and a 6.2" or maybe even a 6.3" rod. I'd either use a LS7 or a L92 top end of course have it all worked over especially if I use the L92.
I kinda got a soft spot for the 400 ci number but I don't like the small bore ones that are out there (well actually I'm hung up on the 4.125" bore) you see I had an OLD ('72) 4 bolt 400ci SBC for years that I was gonna build and put into something but I got distracted by the LS1's and sold it well now I want to put a 400 in the X. It's gonna be a DD and I want to keep it to where I feel it's gonna be durable ie. why I'm concerned about the rod ratio.
Really I'm just kicking the idea around.
08-23-2006, 07:47 PM
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Originally Posted by firefighter
SS thats kinda what I was thinking the situation is. I gotta find out if they just want my first born or if they want my nuts too.
Chuntington what I got going in my head is to basically build a 400ci with a good rod ratio 4.125" bore 3.75" stroke and a 6.2" or maybe even a 6.3" rod. I'd either use a LS7 or a L92 top end of course have it all worked over especially if I use the L92.
I kinda got a soft spot for the 400 ci number but I don't like the small bore ones that are out there (well actually I'm hung up on the 4.125" bore) you see I had an OLD ('72) 4 bolt 400ci SBC for years that I was gonna build and put into something but I got distracted by the LS1's and sold it well now I want to put a 400 in the X. It's gonna be a DD and I want to keep it to where I feel it's gonna be durable ie. why I'm concerned about the rod ratio.
Really I'm just kicking the idea around.
Chuntington what I got going in my head is to basically build a 400ci with a good rod ratio 4.125" bore 3.75" stroke and a 6.2" or maybe even a 6.3" rod. I'd either use a LS7 or a L92 top end of course have it all worked over especially if I use the L92.
I kinda got a soft spot for the 400 ci number but I don't like the small bore ones that are out there (well actually I'm hung up on the 4.125" bore) you see I had an OLD ('72) 4 bolt 400ci SBC for years that I was gonna build and put into something but I got distracted by the LS1's and sold it well now I want to put a 400 in the X. It's gonna be a DD and I want to keep it to where I feel it's gonna be durable ie. why I'm concerned about the rod ratio.
Really I'm just kicking the idea around.
08-23-2006, 09:36 PM
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Firefighter,
You may not be aware of this, but the 400SBC had the "worst" rod ratio of any conventional American V-8 with a rod/stroke ratio of 1.484.
Coming in close tying for second place is BBC 454 and 502's at 1.533. None of these engines had any real issues that would keep anyone from building them.
Many, many moons ago performance engines used production heads, which we all know they were horrible flowing (especially by today's standards).
Long rod ratios (aka "good rod ratios") helped these heads flow more air to make more power. Nowadays, even production heads flow good, and thus the need to enhance flow from long rods is negated. Long rods only help today when you can shave excessive piston weight, beyond that, don't bother.... there's not enough to potentially gain to waste one's time.
As git_sum has said, don't worry bout r/r. I put in the stroke I *need*, make the compression height on the piston what I *need*, and fit a rod between the two, and not let the rod ratio bother me.
I've attached a rod ratio chart, it's kinda interesting how the r/r's are all over the map.
You may not be aware of this, but the 400SBC had the "worst" rod ratio of any conventional American V-8 with a rod/stroke ratio of 1.484.
Coming in close tying for second place is BBC 454 and 502's at 1.533. None of these engines had any real issues that would keep anyone from building them.Many, many moons ago performance engines used production heads, which we all know they were horrible flowing (especially by today's standards).
Long rod ratios (aka "good rod ratios") helped these heads flow more air to make more power. Nowadays, even production heads flow good, and thus the need to enhance flow from long rods is negated. Long rods only help today when you can shave excessive piston weight, beyond that, don't bother.... there's not enough to potentially gain to waste one's time.As git_sum has said, don't worry bout r/r. I put in the stroke I *need*, make the compression height on the piston what I *need*, and fit a rod between the two, and not let the rod ratio bother me.
I've attached a rod ratio chart, it's kinda interesting how the r/r's are all over the map.
08-23-2006, 09:48 PM
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Before anyone flames me..... the chart does not include the newer LS Family of engines. I'll have to update it tomorrow and repost it, 'cause it just hit me that the current production LS7 has the 2nd worst ever r/r with 1.518. 
Update: I said screw it, I can sleep later and fixed the chart to include 4.8L thru 7.0L LS engines.
Update: I said screw it, I can sleep later and fixed the chart to include 4.8L thru 7.0L LS engines.
Last edited by LSX Wizard; 08-23-2006 at 10:09 PM.
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08-23-2006, 10:33 PM
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Yeah guys I know the ole 400's had a terrible r/r thats why I kinda thought it would be cool to make a "new 400ci" that would have a good r/r. Now I didn't realize that it had minimal if none at all use on the new LSx stuff.
But all in all I wonder if I really need a 427ci maybe a warmed over LS2 is enough it's just gonna be a DD. I'll get crazy on the next motor.....
But all in all I wonder if I really need a 427ci maybe a warmed over LS2 is enough it's just gonna be a DD. I'll get crazy on the next motor.....
08-24-2006, 02:26 PM
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I'm sitting on an offset ground stock crank that has a 3.822" stroke using Acura rod journals (1.888" diameter) with Carrillo forged rods and 4.080" Diamond pistons. My plan is to use it with an L92 block on the stock sleeves. This makes a perfect 400 cid and should rev to the moon and put out awesome power with the short stroke and low friction rods used by NASCAR... If anyone is interested in this set-up I might sell it...
Shirl Dickey
SD Racing Enterprises
Shirl Dickey
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08-24-2006, 02:58 PM
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FWIW I belive darton makes a 4.2 sleeve now.
That paired up with a stock crank would put you right at a 401, plus with the bigger bore you can open up the heads more.
That paired up with a stock crank would put you right at a 401, plus with the bigger bore you can open up the heads more.
08-24-2006, 06:06 PM
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Originally Posted by Camaro_Zach
that setup would rule.
08-24-2006, 10:29 PM
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Originally Posted by MrEracer
I'm sitting on an offset ground stock crank that has a 3.822" stroke using Acura rod journals (1.888" diameter) with Carrillo forged rods and 4.080" Diamond pistons. My plan is to use it with an L92 block on the stock sleeves. This makes a perfect 400 cid and should rev to the moon and put out awesome power with the short stroke and low friction rods used by NASCAR... If anyone is interested in this set-up I might sell it...
Shirl Dickey
SD Racing Enterprises
Shirl Dickey
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Nate
08-27-2006, 12:46 PM
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Originally Posted by firefighter
Now I didn't realize that it had minimal if none at all use on the new LSx stuff.
