Rod alignment

General engine tech -- Drag Racing to Circle Track

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Steve.k
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Re: Rod alignment

Post by Steve.k »

Chevies are special all right!! Lol
elwood
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Re: Rod alignment

Post by elwood »

who doesn't get that transmitting power in a straight line isn't more efficient than offset?
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Re: Rod alignment

Post by swampbuggy »

How does the accuracy of the crankshaft manufacturing----( the location of the centerline of the rod journal in relation to the bore centerline) AND the accuracy of the production of the engine block----the centerlines of each bore in relation to where the centerline of the con-rod is SUPPOSED to be effect what is being discussed ?? :?
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Re: Rod alignment

Post by blykins »

All of that absolutely plays into it.

The picture that the guy posted doesn't look any different than the pictures of my setups with Scat, Compstar, and Oliver rods.

Gotta look for new ways to sell parts I guess.
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Steve.k
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Re: Rod alignment

Post by Steve.k »

IMG_2419.PNG
. This is a rpm crank and scat rod on 351w. Definitely off center.A fair bit more than molnar set up. Freind of mine just bolting this one up.
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MadBill
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Re: Rod alignment

Post by MadBill »

All in favor of piston-guided rods, raise your hand..
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
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modok
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Re: Rod alignment

Post by modok »

elwood wrote: Sat Mar 17, 2018 8:56 pm who doesn't get that transmitting power in a straight line isn't more efficient than offset?
The "straight line" between the piston and the main bearing? :P :wink:
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Re: Rod alignment

Post by LSP »

MadBill wrote: Sun Mar 18, 2018 10:33 pm All in favor of piston-guided rods, raise your hand..
:hello2:
Steve.k
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Re: Rod alignment

Post by Steve.k »

I understand prostock and NASCAR use those piston. Is it for controling the big end as they are narrowed up and/ or centering rod? Must be hp in both I would say.
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Re: Rod alignment

Post by swampbuggy »

I wish somebody would post pictures of a piston guided rod deal and explain exactly WHY it is done, more power i know BUT WHY does it help ?? What is gained (or) done away with by doing it. I understand certain things can not be talked about so hopefully it is NOT still a confidential topic. How about it Warpspeed ??? Mark H. :)
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Re: Rod alignment

Post by peejay »

Thinking about it, if one were to guide the rod by the piston, there is very little relative motion on the sides at the piston (small diameter pin, only a handful of degrees of rotation back and forth) and there is a lot of relative motion at the sides at the crank (much larger pin, 360 degrees of motion every revolution), so piston guided should reduce friction.

Another thing, is if the crank is whipping around every which way because it's a two foot long steel noodle, if you are guiding the rods with the crank, the pin end is going to want to move side to side a lot, which would result in the piston wanting to cock over. If you guide by the piston, the piston would stay more square in the bore, which means better ring seal, tighter clearances can be kept, etc.

Just some outside observer hypothesizing.
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Re: Rod alignment

Post by Steve.k »

swampbuggy wrote: Mon Mar 19, 2018 8:08 pm I wish somebody would post pictures of a piston guided rod deal and explain exactly WHY it is done, more power i know BUT WHY does it help ?? What is gained (or) done away with by doing it. I understand certain things can not be talked about so hopefully it is NOT still a confidential topic. How about it Warpspeed ??? Mark H. :)
Here is what centered pistons are like.http://www.ebay.com/itm/like/3119372966 ... noapp=true
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Re: Rod alignment

Post by pamotorman »

can there be less friction from the smaller area of the wrist area of the rod and piston making contact vs the larger area of the crank and rod faces making contact ?? some 2 stroke engines used guided rods in the piston to maintain the side clearance on the rod big end to get lubrication into the needle bearings
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Re: Rod alignment

Post by swampbuggy »

So i guess it is safe to say with todays current HIGH quality pistons which are run with tighter than ever before clearances along with just enough clearance to be safe between the rod small end sides and the piston, we have a piston controlling the movement of the connecting rod for WHAT reason ???? Mark H. :?
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Re: Rod alignment

Post by Steve.k »

Nascar from what I understand uses it as they trim thickness of big end. That way less friction and weight. The two strokes I've worked on also hold the rod dead center on pin. The rod is shimmed on both sides to center. Im not sure if nascar sees gains from the smaller big end or from the rod being aligned perfectly straight or both. This is what we are trying to determine. My thinking the more you have everything lined up you free hp. But unfortunately i have made mistakes before so could be wrong.
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