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Old 12-28-2002, 09:55 AM
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Post connecting rods

What would the benefit be of using a 6 inch rod versus a 5.565,which is what i have now.

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Old 12-28-2002, 10:39 AM
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depends on your block... AFAIK, you can't fit 6" rods in a SBC without machining, and it usually makes for more headaches than benefits... 5.7 might work, don't know offhand.
sorry, didn't help much
-z-
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Old 12-28-2002, 10:44 AM
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What's the size of the engine and what are you lookin to do with it? Wolf is right w/6.0 rods there will be machining involved. I'm almost certain that 5.7s will work in a sbc.
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Old 12-28-2002, 10:48 AM
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That rod 5.565 that your talking about is from a 400 sbc.
If you want to use a longer rod you need to get the rods ground for a 5.7" or 6" rod, with different pistons.

[ December 29, 2002: Message edited by: 1BAD80 ]</p>
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Old 12-28-2002, 11:51 AM
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Take a pencil and paper, draw a piston, draw the pin location in the piston, now draw your crankshaft centerline with a circle, and draw the rod journal out to the side, now connect the two {this is your imaginary rod.} Now draw a new picture, this time using a longer rod. You'll notice, that if you draw your two pictures to scale, that you have to move the location of the piston pin further up in the piston, this also makes the angle of the connecting rod smaller.
What the longer rod accomplishes, is it reduces side loading forces on the cylinder wall, it also changes the way the piston accelerates throughout the rotation cycle, it allows the piston to dwell longer at Top Dead Center, which in turn allows combustion pressures to act on it for a longer period of time, and hence, producing more power.
Smokey Yunick made a big to-do about the benefits of longer rods in an engine several years ago in his book, Power Secrets, but I think he exaggerated it's benefits, Power, and longevity increase with a longer rod. The long stroke of the 400 needs help in this area, because it's stock rod/stroke ratio is poor, so 5.7s or 6.0 rods here will be a big benefit vs. the short, 400 rods. Troy, remember though, if you already have the short rods in your engine, there are alot of pretty stout running 400s out there with the short rods. Oh, and you can use your stock 400 crank with 350 rods, you should "cam cut" the inside, upper portion or the rod bolt, and just a little on the rod to avoid contact with your camshaft, most machine shops know how to do this.
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Old 12-28-2002, 12:55 PM
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I have the stock 400 rods out,and have access to 5.7 inch rods,would the.135 make a differance?
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Old 12-28-2002, 04:33 PM
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I have run both the stock rod and a 5.7 rod. I made other changes also so I cannot say that the rods alone made the difference in the two 400s. But I do know the 5.7 rod motor has the same heads and intake and cam and is crisper on throttle response. Such as the theory of the longer rod should do. I know a good set of Pink rods with ARP bolts are a great budget swap into the 400. I use a small base circle cam to help with clearence issues. Great response NAIRB.
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Old 12-29-2002, 07:35 AM
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This is all good info,I'm assuming the clearance problems with 5.7 rods are because of the difference in the rod and rod bolt profiles? It's pretty obvious there's a big difference.
I put a set of 6" Eagle rods along with a matching Eagle crank in a 400 awhile back, I had to take some metal off the block where the outer rod bolt on #7 was nicking right by the pan rail.After that I was checking everwhere for clearance problems, and didn't find any, I guess for the $$$$$ Eagle must do they're homework!
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Old 12-29-2002, 09:21 AM
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Most aftermarked rods are designed to clear blocks and cams. I ran 6" Eagles in my 400 and did not have any problems. Not even close.
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Old 12-29-2002, 09:31 AM
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So if i can afford it i should go with the longer rods.Depending on what compression i want to run.

[ December 29, 2002: Message edited by: Troy ]</p>
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Old 12-29-2002, 10:14 AM
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Good responce NAIRB this should go into the knowledge base for referance.
George
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