6" vs. 5.7" rods for a sbc 383 question

Old 05-24-2007, 04:15 PM
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lmccoll
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Default 6" vs. 5.7" rods for a sbc 383 question

Everything I have read or heard says a 6" rod for 383 sbc is the best way to go. My question is, if it is better, why do they make 5.7" kits? Is it so people can reuse rods out of a 350 if they have them?
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Old 05-24-2007, 04:45 PM
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buffjhsn1
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i don't think there is a definate answer for this. you will be opening a can of worms here! lol. there are people that think that one piston to rod ratio is optimum, it depends on ring placement , motor application etc....then you get into side load of the piston and so forth...i feel it's all about the same...
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Old 05-24-2007, 04:52 PM
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slowman
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like buffjhsn1 said you will get different answers. but i always use the 5.7 rod if i'm building a nos engine and use the 6 if it's going to be n/a. you need the comp height for a good ring pack on a nos engine so i use the 5.7.
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Old 05-24-2007, 05:10 PM
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dcarr511
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Do the pistons for the 5.700" rod have the wrist get into the oil rings like the 6.00" do ? I just bought a 383 rotating assembly w/ 6.000" rods and it has the Oil ring supports.

Being that mine is intended for street use and maybe a couple of passes at Maxton N.C. on a standing mile course I now wish I would've gone with a 5.700" rod. That way the ring package could've been placed lower. And if the 5.700" doesnt put the wrist pin into the oil rings I think it would've been the better choice for me. If they do then it doesnt matter ....

The other issue I have is that the piston skirt is real short, something else I dont think is best for a street engine.

Is your engine going to be used for street / track or both ?
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Old 05-24-2007, 05:42 PM
  #5  
slowman
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dcarr, the ring support isn't the big problem the extra .300 you can pull the top ring down from the heat the better.. if it's a n/a engine then i wouldn't worry about it inless it's realy high compression.
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Old 05-24-2007, 05:53 PM
  #6  
lmccoll
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Default 6" vs. 5.7" rod for 383

This is going to be a drag strip only engine. I plan to go with a forged bottom end, 11.5:1 compression because I can get racegas 101 octane local. I already have heads, intake etc. I plan to make 500 to 550 hp.
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Old 05-24-2007, 06:04 PM
  #7  
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are you going to spray it at all? if you are then buy the 5.7rod.
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Old 05-24-2007, 11:10 PM
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edvancedengines
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Monkey See-Monkey Do
Everything I have read or heard says a 6" rod for 383 sbc is the best way to go
Back in the mid 1950's Smokey Yunik discovered what was considered to him as the ideal rod length/stroke ratio. Most of the automotive engineers of the day agreed with him or listened to him.

At the time and in the style of racing competition he was in, there is little doubt that his findings were correct for his specific applications.

This fallacy of ideal rod length/stroke ratio was perpetuated by the many racing performance magazines and still is. Racers and even most engine builders believe what they see written in print in the magazines.

I like the philosphy of David Reher about this. "The connecting rod connects the piston to the crankshaft. That is it" Noting trick about rod lengths.

There is always a trade off with a short rod vs a long rod. Each one had advantages and each one has disadvantages. I build with both.

I like the idea of the piston configuration being far more important. Longer rods will allow shorter and lighter pistons, but at times you don't want a short piston.

I have built short rod 383 strokers, 5.565 rod, medium rod strokers, 5.700 rod and long rod strokers 6.00 rods in the 383 configurations. As far as horse power potential, I can't see any difference.

Do not be concerned about the having to use ring support rails. no biggie. Just prep and clean cylinder walls. with as clean of proceedures as possible and do a final clean with lacquer thinner or acetone followed with a light wipe of WD 40. Keep it all clean.

When you fire it up do not let the engine to idle at any low speeds and do not even let it idle long at higher speeds. Even idling at higher speeds, blip the throttle from time to time to load the rings some. After it runs for 30 minutes kill it change and check the oil filter and just let it all cool down completely. Check the valve adjustments, head bolt torque and fire it back up aftr it has fully coooled. This time you can let it idle a little lwer and begin to adjust tunings. eventually let it idle at as low of rpm as it can and adjust tunings for idle. Idle it back to where it will run. Let it all get cool again. Check all intake and header bolts and re-torque. Now you are ready to put it underr load either on the road or the dyno. Do not let it idle long. Try to keep it under a load with short bursts of full throttle. Check oil filter and change and check oil. Enjoy.

Ed
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Old 05-29-2007, 10:01 AM
  #9  
Robert1320
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Originally Posted by edvancedengines
Monkey See-Monkey Do
Everything I have read or heard says a 6" rod for 383 sbc is the best way to go
This fallacy of ideal rod length/stroke ratio was perpetuated by the many racing performance magazines and still is. Racers and even most engine builders believe what they see written in print in the magazines.

I like the philosphy of David Reher about this. "The connecting rod connects the piston to the crankshaft. That is it" Noting trick about rod lengths.
"The connecting rod connects the piston to the crankshaft."
That is what rods are for!

ED
That is the truth. Rods are rods. Not much more.
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