5.7 vs 6.0 Rods

General engine tech -- Drag Racing to Circle Track

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Stan Weiss
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Post by Stan Weiss »

Talking about rod length without stroke just adds another variable to the equation. I believe that an increase in rod/stroke ratio will help an engine that is under headed for its ci size / RPM range.

Code: Select all

          5.7" rod              6.0" rod
stroke  rod/stroke ratio     rod/stroke ratio
3.00"    1.9:1
3.25"    1.738:1              1.846:1
3.48"    1.638:1              1.724:1
3.75"    1.52:1               1.6:1
Stan
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Post by falcongeorge »

Stan Weiss wrote:Talking about rod length without stroke just adds another variable to the equation. I believe that an increase in rod/stroke ratio will help an engine that is under headed for its ci size / RPM range.

Code: Select all

          5.7" rod              6.0" rod
stroke  rod/stroke ratio     rod/stroke ratio
3.00"    1.9:1
3.25"    1.738:1              1.846:1
3.48"    1.638:1              1.724:1
3.75"    1.52:1               1.6:1
Stan
Or running a lower r/s ratio benefits a package that has too much port volume. All a matter of perspective...
jpankey
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no dyno just seat of the pants

Post by jpankey »

short rods acelerate quicker but nose over sooner.
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af2
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Post by af2 »

CNC BLOCKS wrote:
Old School wrote:What are the differences in the cams you use for a 5.7 rod compared to the 6 inch rod?
It depends on the combination but rememeber that going from a 5.7 to 6.250 the engines is going to breath differently!!! And to optimize you can't run the same cam for both rod lenths.

Carl, exactly!!!
GURU is only a name.
Adam
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Post by Sprinter99 »

CNC BLOCKS wrote:
Sprinter99 wrote:Over the last few years i've had 5.85 ,6.0 and 6.125 rods in 355s and the longest rod made the MOST power on the dyno but was SLOWEST on the track, the 5.85 made LESS peak power than both the other two but was MUCH faster off the corners than the 6.125. A big example of we dont race dynos.
Hopefully your not using the same cam for a short and long rod engines!
Believe it or not the out of the 4 different cams we tried in them the 6.125 and 5.85 made the most with the same crower 00432 cam,the 6.0 did best with an ultradyne and was the all around best of the 3 even though the 6.125 made a whopping 6 more hp :lol: . I wouldnt consider any of the stuff i build for myself calculated or optimized , more like screw it lets try it and see what happens.
Kurt Summers
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Post by SKeown »

Kurt, you're approach seems crude, but that's likely how most discoverys are made.

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jimivice

5.7 rod vs 6.00 - speed

Post by jimivice »

This has been a much debated subject. Jenkins stated that the rod length or rod ratio is an integral part of the induction system. He generalized that a comparatively long rod for a given C.I. (ie 5.7" to 6.125") the longer rod benefited smaller runner volumes and/or restricted int. systems. Large int. runners liked a shorter rod. Smokey stated,"Put in the longest damn rod you can". David Reher says do not get caught up in connecting rod length. I think the physical confines of the block will be the determining factor. The 383 s/b chevy, despite its' success and popularity, is limited. Most engine builders prefer a 6" rod to reduce rod angularity and the the lighter piston because of the short compression hgt. If you are using the stock rocker arm ratio, lobe lift is a concern because of the cam location. If the rod does not have a cam cut then it will have be modifyed. You will have to use oil ring spacers because the pin runs into the ring land. I have built my fair share of variations of the 383 chevy with good results. I favor the 6" rod to reestablish the rod ratio lost by the longer stroke. The ratio is close with the longer rod and longer stroke but the engine will not have the same characteristics. The first consideration in determining the C.I.- is the block and the bore/stroke ratio. Then everything-else is based on maximizing your combination. It is easier said than done.
The Dark Side of Will
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Post by The Dark Side of Will »

I've had a question about this for a while...

http://www.airflowresearch.com/articles ... /A3-P1.htm

What do you guys think of the engine in that article? Can you really run higher compression with longer rods? That is, of course assuming that quench, chamber/piston polishing and coatings are the same...

An engine like that could be built much more easily nowadays using 6.250 rods and shelf pistons for a 400 with 6" rods instead of the 6.209 Ford rods and custom pistons.
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Post by new engine builder »

The Dark Side of Will wrote:I've had a question about this for a while...

http://www.airflowresearch.com/articles ... /A3-P1.htm

What do you guys think of the engine in that article? Can you really run higher compression with longer rods? That is, of course assuming that quench, chamber/piston polishing and coatings are the same...

An engine like that could be built much more easily nowadays using 6.250 rods and shelf pistons for a 400 with 6" rods instead of the 6.209 Ford rods and custom pistons.
I stopped reading when they said 400 block.
The 400 sbc is the biggest P.O.S GM ever put out.
I have over twenty 400 blocks that have "rod windows" or holes in the lifter valley that sit all over the shop floor as a reminder of why we use what we use today.
Sure, they might live in a street car or a drag car for a few seconds at 7,500.
Try taking one down both the back stretch and the front stretch of a "tacked-up" dirt track only lifting engough to "set" the car for the corner on a large 1/2 mile track.
You might get 10 nights out of one or 10 seconds.
It's not a question of if, it's when.
Either use a Dart SHP block or an old 010 4-bolt block for a starting point.
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Post by Warp Speed »

new engine builder wrote:I stopped reading when they said 400 block.
The 400 sbc is the biggest P.O.S GM ever put out.
I have over twenty 400 blocks that have "rod windows" or holes in the lifter valley that sit all over the shop floor as a reminder of why we use what we use today.
Sure, they might live in a street car or a drag car for a few seconds at 7,500.
Try taking one down both the back stretch and the front stretch of a "tacked-up" dirt track only lifting engough to "set" the car for the corner on a large 1/2 mile track.
You might get 10 nights out of one or 10 seconds.
It's not a question of if, it's when.
Either use a Dart SHP block or an old 010 4-bolt block for a starting point.
Good rod length/ratio info right there! :D
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Post by SKeown »

Why such long rods in NASCAR, piston weight?

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Post by falcongeorge »

Warp Speed wrote:
new engine builder wrote:I stopped reading when they said 400 block.
The 400 sbc is the biggest P.O.S GM ever put out.
I have over twenty 400 blocks that have "rod windows" or holes in the lifter valley that sit all over the shop floor as a reminder of why we use what we use today.
Sure, they might live in a street car or a drag car for a few seconds at 7,500.
Try taking one down both the back stretch and the front stretch of a "tacked-up" dirt track only lifting engough to "set" the car for the corner on a large 1/2 mile track.
You might get 10 nights out of one or 10 seconds.
It's not a question of if, it's when.
Either use a Dart SHP block or an old 010 4-bolt block for a starting point.
Good rod length/ratio info right there! :D
x2 :lol:
bigjoe1
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Post by bigjoe1 »

I dont know if anyone has mentioned it, but long rods allway make more HP above the HP peak. This is a good reason alone to run longer rods if you want to extend the RPM range where the engine still make power


JOE SHERMAN RACING ENGINES
The Dark Side of Will
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Post by The Dark Side of Will »

new engine builder wrote: I stopped reading when they said 400 block.
Then you *COMPLETELY* missed the point...
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Post by new engine builder »

The Dark Side of Will wrote:
new engine builder wrote: I stopped reading when they said 400 block.
Then you *COMPLETELY* missed the point...
UMMM,I got the point.
They want me to shove a HEAVY ROD in a junk 400 block.
How cares about rod ratio when you are putting it into a junk block. :roll:
WHY BOTHER!!!!
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