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Robotin

m10 build with strange thought

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hey everyone!so doing some looking around tonight. would it be possible to run the 144mm H rods with the stock 2.0 crank? with either stock pistons or the IE cast pistons. could u bump up compression with that?

or is it just impossible?

breakdown:

IE 144mm rods on 2.0 crank with IE 9.5:1 cast pistons?

or

IE 144 rods on 2.0 crank with any type of pistons/head?

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I don't think so. Longer rods would require a longer stroke, no? Now, I suppose you might be able to make up the distance with custom pistons. Maybe.

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To run the 144mm rods, talk to Jeff Ireland.

He's a big proponent of long rods with a custom piston.

So was Smokey Yunik.

It reduces side thrust on the piston...

...but you have to run a custom piston.

t

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Long rod + higher piston pin height is better if you can achieve it without sacrificing ring sealing/piston strength. decrease in side thrust is the main reason; look at it this way, if you could theoretically have an infinitely long connecting rod, you would have zero side thrust. Less side thrust means bores and rings wear more slowly and less blow through as rings are more able to keep flush with the bore. I'm a big fan of square or slightly oversquare motors with long rods... They are more reliable and run very smoothly. Stroking can achieve a nice increase in displacement (and as a direct result, torque) but the increase of piston speed means a lower safe redline.

I could get into far more detail here, but it really comes down to what you want to achieve and how much you want to spend.

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Stock pistons - no.

Custom pistons - yes.

Does it raise compression - no, but then you can get the pistons for the CR you want.

I'm running 146mm rods with JE-pistons and stock crank. Not sure about benefit but I believe it helps when reaching for high revs and reduces piston side forces (->wear) a bit.

Tommy

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I think it's one of those things-

if you're going to buy custom pistons and rods anyway,

there's no reason to go with as long a rod as you can while keeping the

sealing package on the piston reasonable.

As long as the rules allow it.

But if you're NOT in the market for both rods and pistons,

you probably won't realize enough added performance

from all the expenditure to make it worth it.

t

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Lemme explain. A longer rod allows for a slowed rate of rod to piston angle when the piston reaches the top. IE.

A piston with a 2" rod vs a piston with a 6" rod. The 2" one in relation to crankshaft angle degrees, push the piston to the top and abruptly jerk it right back down. The 6" rod has a much longer transition from going up to going down and thus does not jerk as hard on the rod. Resulting in less overall piston acceleration and less wear. This is important due to the relatively long stroke of the m10 motor compared to say a honda.

Here are all the differences.

http://www.e30m3project.com/e30m3performance/tech_articles/engine-tech/rod-ratio/index.htm

http://www.rustpuppy.org/rodstudy.htm

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Guest Anonymous

To answer your question - NO

The stock rod is 135mm so the 144mm is 9mm longer. With a stock piston and 144 rod the piston will finish 4.5mm above the deck.

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Actually if the rod is 9mm longer and you are running the same piston and crankshaft then at top dead center the piston will be sticking 9mm out of the top of the block at TDC. It will also be 9mm higher at BDC. If you want to run a longer connecting rod you must move the wrist pin in the piston up in relation to the piston dome the exact same amount as you lengthen the rod.

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everyones opinions are greatly appreciated. i am exploring around and seeing how many differentl things i can throw in am engine what differences those make.

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