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Old 12-13-2011, 04:01 PM
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question about rod length

I have a 427 bbc that is bored .60 over right now I have a rod length of 6.135. I was wanting to know if I put a longer rod in it what would happen?? I am not the brightest light in the shop but I can do anything with a little help LOL . SO that's why I am asking questions before I start building

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Old 12-13-2011, 04:42 PM
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Longer rods take pistons made for them, so one thing that will happen is your bank balance will suffer. Putting in longer rods, most of the time, is a waste of time and money, unless you're building an all out race engine. And even then you get different opinions.
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Old 12-13-2011, 04:45 PM
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it is an all out race motor. I'm using it in my jeep. its for mudd bog competition
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Old 12-13-2011, 04:51 PM
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Rod length

What he said. However, if you have any future plans for building a bigger engine and, would be reusing parts and, need to buy rods and/or pistons now, a 6.385 rod is a lot friendlier to most combos. If you're just doin' a refresh, I'm sure what you have is fine.
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Old 12-13-2011, 04:53 PM
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??

All out race? What's with the SBC parts in the pic?
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Old 12-13-2011, 04:57 PM
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lol I don't know where that pic came from. I will look into getting rid of it soon. I am rebuilding the bottom end. I'm putting all new parts in it except for the crank
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Old 12-13-2011, 04:58 PM
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If you NEED rods, the .250 long would be a good choice since it will work with a 496 cid combo. You said the engine is bored, so I take it you have pistons and the finish bore is particular to those pistons. It's hard to get new pistons that would like your bore and you would need them for the longer rod. My advice is; save your money, run what you got and the next time it needs freshened, do the 496 kit.
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Old 12-13-2011, 04:59 PM
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Mudder!!

Yea. I used to know a bunch of those guys. Know of Rodney Covington? (he's featured in the "And They Walked Away" videos") Just make it grunt. You're only goin' 130 feet...unless they changed that. Carb? Injected? Gas? Alky?
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Old 12-13-2011, 05:15 PM
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the pit we run is 200 ft. I wasn't sure if I cud run new pistons in the bore I have. I'm nesting up the bottom end of my motor. right now I have I beam rods that are press fit. I wanting to yo to H beam rods. but from what I have seen is the are floating.
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Old 12-13-2011, 05:38 PM
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if I use file to fit rings won't that make up the difference from the bore to the new pistons?
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Old 12-14-2011, 05:17 PM
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If I use file to fit rings and the same type of piston will that be ok?? I know they are not all made the same but I was curious if they would still work with file to fit rings???
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Old 12-14-2011, 07:31 PM
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Quote:
Originally Posted by inquiring_mind2
if I use file to fit rings won't that make up the difference from the bore to the new pistons?
There are at least 2 things to consider.
1. piston to cylinder wall clearance (which cannot be altered by ring gap). Usually 0.001" to 0.002" for a cast or hypereutectic piston, 0.003" to 0.007" for forged pistons (just ballparking for newbies).
2. ring end gap (determined by the use of the motor) 0.0045" of gap per inch of bore to 0.008" of gap per inch of bore. Top ring gaps usually vary from second ring gaps.

Scroll down here and read Tech Tip 2005. It is rod lengths discussed by Ron Iskenderian, son of the famous Ed Iskenderian cam grinder...
http://www.iskycams.com/techtips.php
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Old 12-14-2011, 07:35 PM
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ok thanks I will check it out. I am using forged pistons. how do I check the clearances?
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Old 12-14-2011, 07:53 PM
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Tell ya what IQ, take a read up on this, it may tell you some things you want to know on long and short rods.
http://www.chevymania.com/
http://victorylibrary.com/mopar/rod-tech-c.htm

The 2nd article is a good read.
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Old 12-14-2011, 08:30 PM
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Best way is to use a bore gauge to find the cylinder diameter and a 4-5 inch micrometer to find the piston diameter. Old school guys like me will turn the piston upside down, insert it into the bore, holding it by the wrist pin and inserting a feeler gauge down beside the piston and cylinder wall. You need to know where the piston is the largest diameter because the skirts are different diameters along the length of the piston. They will usually be the largest on the skirt opposite the wrist pin or close thereby. Just keep swapping out thicker and thicker blades until you get a snug fit. That will be the piston to wall clearance.
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