Anyone know the cylinder to cylinder offset for BB's?
#850774
11/10/10 09:53 PM
11/10/10 09:53 PM
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Joined: Jun 2008
Posts: 577
Arkansas
Adrielp
OP
mopar
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OP
mopar
Joined: Jun 2008
Posts: 577
Arkansas
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Okay, so I have taken hand measurements using a tap measure and digital caliper but its still hard to approximate exactly what the offset is. I calculated between 0.5-0.5842893 in of offset based on the deck offset in the valley pan area. I need to approximate these values as closely as I can so that my design are geometrically correct. If you can have the answer to this question or can point me in the right direction, please respond. Any and All information is appreciated!
Thanks!
Last edited by Adrielp; 11/10/10 09:58 PM.
Adriel Paradise
Substation Design Engineer III
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Re: Please Help: Does anyone know the cylinder to cylinder
[Re: Adrielp]
#850775
11/10/10 09:56 PM
11/10/10 09:56 PM
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Joined: Jul 2010
Posts: 3,502
SOUTH JERSEY
HEMIFRED
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master
Joined: Jul 2010
Posts: 3,502
SOUTH JERSEY
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WHAT EXACTLY ARE WE TRYING TO LEARN HERE ?
the offset of cylinders on opposite banks ?
then we need to know what motor
home of the
Sox and Martin Hemi Duster
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Re: Please Help: Does anyone know the cylinder to cylinder
[Re: HEMIFRED]
#850776
11/10/10 10:12 PM
11/10/10 10:12 PM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
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Marysville, O-H-I-O
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it sounds like that's what he's asking...but aren't all the big blocks the same offset? you can take a 440 crank and drop it into a 383, and it fits, as long as you turn the mains down.
How wide is the rod journal on the crank...isn't the offset half of that? that's why the offset is there anyway, so the opposite banks can use the same rod journal
**Photobucket sucks**
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: Adrielp]
#850781
11/10/10 11:15 PM
11/10/10 11:15 PM
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Joined: Sep 2005
Posts: 1,329
St. Louis, MO
mopardamo
pro stock
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pro stock
Joined: Sep 2005
Posts: 1,329
St. Louis, MO
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Hello, Sounds like a great project. Good luck. Do you have any flow numbers modeled? 600cfm+ would be a good nich to fill. Damon 
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: Adrielp]
#850782
11/10/10 11:20 PM
11/10/10 11:20 PM
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Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
Performance Only
top fuel
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top fuel
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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it sounds like you have some ambitious plans. of course you should expect some of the purists to berate and ridicule if your design ever comes to fruition. after all, that's what they do to Mopar guys with Predator heads.  it's kind of a shame actually. i can get you the info you need in a few days when i have time. if your interested, pm me your ph.# and i'll call you with it.
machine shop owner and engine builder
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: Performance Only]
#850783
11/10/10 11:28 PM
11/10/10 11:28 PM
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Joined: Jan 2003
Posts: 3,887
Smyrna, South Carolina
STEFF
master
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master
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Smyrna, South Carolina
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Quote:
of course you should expect some of the purists to berate and ridicule if your design ever comes to fruition. after all, that's what they do to Mopar guys with Predator heads.
In regards to the Purists:
"Those Guys are FAGS!!!"
Good Luck with your project!! The Mopar hobby needs more forward thinkers.......
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: AndyF]
#850785
11/11/10 02:17 AM
11/11/10 02:17 AM
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Joined: Oct 2007
Posts: 4,219
New York
polyspheric
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master
Joined: Oct 2007
Posts: 4,219
New York
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that those engines were designed in the 1950's by engineers working on drafting boards. A lot of dimensions are 1/16, 1/32, 1/64th etc.
Some were even carried over from the original patent holder who used metric (Zenith carb), but the precision is not that much coarser than we use today: a cam or journal is still to .0001", a stem or bore to .001".
The offset on most V engines is pretty close to 1/2 the journal width, which is also the rod width + 1/2 of the side clearance, or about 1.020-025" in a B/RB.
Boffin Emeritus
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: Adrielp]
#850786
11/11/10 08:50 AM
11/11/10 08:50 AM
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Joined: Nov 2003
Posts: 2,715
closer to Canadian beer!
torkrules
I'm neurotic
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I'm neurotic
Joined: Nov 2003
Posts: 2,715
closer to Canadian beer!
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Quote:
Quote:
can you tell us the reason you need to know that dimension, or is it top secret?
Not top secret at all. I'm currently a college student and have been around drag racing my entire life. I'm also a mopar fan and as such, I became very frustrated with the lack of splayed valve head selections for a BB mopars so I decided to try to design one. Well, that has come close to completion but in doing so I have made a some changes that require designing and intake manifold and valley pan, but in the process of doing so I want to verify that the measurements I had were approximate. Right now, this is just a design, so now I'm trying to finalize design so that I can run analysis and see if my design is worth trying to mass produce.
Might be worth your while to find a metrology outfit that has a CMM machine. I used to use one in my last job. What an awesome piece of technology. I used to use it to set up rear diffs. This will tell you everything dimension you need to know about an engine block.
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: AndyF]
#850787
11/11/10 09:55 AM
11/11/10 09:55 AM
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Joined: Jun 2008
Posts: 577
Arkansas
Adrielp
OP
mopar
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OP
mopar
Joined: Jun 2008
Posts: 577
Arkansas
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Quote:
Quote:
Okay, so I have taken hand measurements using a tap measure and digital caliper but its still hard to approximate exactly what the offset is. I calculated between 0.5-0.5842893 in of offset based on the deck offset in the valley pan area. I need to approximate these values as closely as I can so that my design are geometrically correct. If you can have the answer to this question or can point me in the right direction, please respond. Any and All information is appreciated!
Your estimated distance with 7 digits of precision is amazing! What were you measuring with, an electron microscope? It is really hard to read those last couple of angstroms isn't it?
Anyway, all joking aside your measurements are off by a bunch. If you think about it a little bit you'll see that the cylinder banks have to be offset from each other by the width of a connecting rod's big end plus a little clearance. I've never measured it myself but it must be a little more than an inch.
When reverse engineering anything on a big block Mopar you have to remember that those engines were designed in the 1950's by engineers working on drafting boards. A lot of dimensions are 1/16, 1/32, 1/64th etc. A few dimensions might be decimal (4.800 bore spacing) but they usually went with fractions.
Andy, I actually measured the distance from the top of the deck in valley pan area where three bolt holes lie from edge to edge. I tried to use a straight edge and tape to for a straight line across the top of the block to the opposite edge. Then approximated the distance using a caliper and measuring tap. When doing so, I came up with .5 inches. The decimals come from my engineering program. I use the .5 inch offset for the center to center of the bolt holes in the valley pan area. But once you extend those angles and form the triangle at the top of the block, you get a with of that exact decimal, so thats how this question came about.
Disregard all of what I just said. I found what I needed this morning. Crank journal with is 2.05. Half of that is 1.02. Now that raises another question. Anybody know how thick the rod bearing side skirts are?
Last edited by Adrielp; 11/11/10 10:04 AM.
Adriel Paradise
Substation Design Engineer III
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: Adrielp]
#850790
11/11/10 02:03 PM
11/11/10 02:03 PM
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Joined: Oct 2007
Posts: 4,219
New York
polyspheric
master
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master
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New York
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I found out that the cylinders were tangent to the actual deck surface
I think you mean "normal" as in "90° away from"?
Tangency refers to having only a single point (objects with no common planes) or line (objects with common 1 plane) of contact.
Boffin Emeritus
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Re: Anyone know the cylinder to cylinder offset for BB's?
[Re: AndyF]
#850792
11/11/10 09:48 PM
11/11/10 09:48 PM
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Joined: Jan 2003
Posts: 16,936
NC
440Jim
I Live Here
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I Live Here
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Quote:
Anyway, all joking aside your measurements are off by a bunch. If you think about it a little bit you'll see that the cylinder banks have to be offset from each other by the width of a connecting rod's big end plus a little clearance. I've never measured it myself but it must be a little more than an inch.
I agree.
The factory rod width is about 1.017". So the bank to bank cylinder offset should be within 0.020" of that number. With a factory rod to rod clearance of about 0.016", 1.017+0.016/2 = 1.025" Just my thinking, not sure.
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