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  #16 (permalink)  
Old 12-17-2007, 10:27 AM
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BS Meter

Nice Meter where'd you find that at?? Good One. LOL!
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  #17 (permalink)  
Old 12-17-2007, 10:28 AM
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Quote:
Originally Posted by dawg
easily get 75 to 100 hp gain depending on heads.
possibly more
and the torque will move up aswell with a longer rod.


Man thats some funny stuff right there... GM spent a big pile of money testing all the nascar engine with rods starting at 5.6" through 6.2" and never found more then 1% difference....And your getting 75hp...

Again post me your dyno sheets showing the A-B-A testing.


Keith
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  #18 (permalink)  
Old 12-17-2007, 10:43 AM
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Quote:
Originally Posted by dawg
easily get 75 to 100 hp gain depending on heads.
possibly more
and the torque will move up aswell with a longer rod.

Are those Special Matched Rods like the tires from the Days Of Thunder Movie??
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  #19 (permalink)  
Old 12-17-2007, 10:57 AM
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Quote:
Originally Posted by SSedan64
Are those Special Matched Rods like the tires from the Days Of Thunder Movie??

They come form the same catalog that sells the 40 hp rocker arms....
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  #20 (permalink)  
Old 12-17-2007, 11:40 AM
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Go with the rods you can get the best deal on. As many have already stated rod length really doesn't matter. Find a piston that will give you the compression you want and pick a rod to fit it.

75-100HP from rod length? Come on now!!
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  #21 (permalink)  
Old 12-17-2007, 12:01 PM
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I Said Also Depends On Heads Aswell!
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  #22 (permalink)  
Old 12-17-2007, 12:19 PM
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Quote:
Originally Posted by dawg
I got 6" rods in my 406
the advantage is a heck of alot more HP
disavantage is youll need different pistons
or you could go with 6" rods and a different crank but youll need some clearancing done which really isnt advisable on a 406 due to the block webbing being thin.
one thing to remember longer rods will give you more power.
This is your first reply, no mention of heads here....
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  #23 (permalink)  
Old 12-17-2007, 12:50 PM
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Quote:
Originally Posted by k-star
This is your first reply, no mention of heads here....
His second reply mentioned heads.

I'd think if a connecting rod swap worked that well a heck of a lot more people would be installing longer connecting rods instead of spending $1500+ on blowers.
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  #24 (permalink)  
Old 12-17-2007, 01:03 PM
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Advantages of longer connecting rods

Longer rods provide for a longer dwell at piston TDC, keeping the combustion chamber small for a longer period as the expanding gases push against the piston. This extracts more power from a given air/fuel mixture thus increasing combustion efficiency. And so much like with good quench, you've once again raised the amount of compression that you can utilize for a given combination (and octane) before detonation becomes a concern. Also, much as does a stroker set-up, longer rods benefit the power band (read "torque curve") with the largest advantages in the low and mid-range RPMs. Even in a stock bore and stroke combination, longer rods can give you some of the effect of a stroked engine. And in fact on a shorter stroke, an even longer rod can be used within the given limits of practicality, this meaning pin location on the piston. While on a pure race engine, particularly such as in a drag race application where run durations are minimal, pin location can be pushed to the limits. But for a long living street engine there are other obvious considerations. Still, with a 350 Chevy (3.48" stroke), a 6.125" rod (5.7" is stock) can be used with no problems, with the correct piston of course. For a 383 (3.75" stroke), you'd probably want to limit it to 6" for street. I use a 6" rod with a 3.80" stroke in my LT1 that does put the pin slightly into the oil ring land. But by using oil ring supports, this is not a big deal.

The reason the 340 Mopar still manages to have a broad and strong torque curve, even with a very short stroke of 3.31" is the fact that this stroke allows it to use rods that are just under 6 1/8". I can't help but wonder if it was simply a cost-saving matter for Chrysler to keep the stroke the same for the 340 as it was in the 273 (and 318) or were they ahead of the curve in experimenting with rod length combinations? Perhaps it was some of each....

One other important benefit of longer rods is that they also reduce side-loading against the cylinder walls. This in turn reduces friction, heat and so of course, wear.
this is all i gotta say about that!
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  #25 (permalink)  
Old 12-17-2007, 01:11 PM
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Nice cut and paste, shame none of it's true..

I'll ask again... show me all your testing results.. Not what your looking up on the net..


Keith
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  #26 (permalink)  
Old 12-17-2007, 01:54 PM
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OK since we have the rods just about figured out, one more question for ya guys,, on a 400 should i go ahead and have it internally balanced? or leave it stock.... what is the ups and downs of having this done..... thanks for the info,
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Old 12-17-2007, 07:58 PM
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Quote:
Originally Posted by dawg
easily get 75 to 100 hp gain depending on heads.
possibly more
and the torque will move up aswell with a longer rod.
That claim is beyond funny. It is just plain incorrect, no matter the heads.

The nice benefit to longer rods is a lighter piston/bobweight. There will be no measureable, significant or seat of the pants torque difference between a 5.7 or a 6 inch rod.
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  #28 (permalink)  
Old 12-17-2007, 08:38 PM
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I would go internally balanced, it might cost you a few more bucks but, I think it's worth it. Keep the weight on the throws and not on the snout and flexplate/flywheel. I have built strokers both ways and never had an issue with either. I have heard/read that internal balancing is easier on bearings but, I have no hard evidence.

Royce
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  #29 (permalink)  
Old 04-30-2010, 11:10 PM
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Rod lenght.

I have had all three, 5.56, 5.7 and 6.0 rod SBC 400's. Other than a lot of expense, never noticed a difference in actual performance gains. the 6" rod 400 required a small base (.900) cam which was expensive. I have actually built a SBC 383 using the stock 400 5.56 rod and stock flat top 350 pistons from Mahle which have a shorter skirt design to clear the crank counterweights. The long rod performance gain on the street is so neglible you will never know it on an engine designed for pump gas. Don't waste your money on long rods for an engine that turns 5500 to 6000 RPM. Just my .23 cents worth (adjusted for inflation).
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