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School me on Pistons....

 
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Old 12-17-2017, 02:55 PM
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Default School me on Pistons....

Looking at a Wiseco piston kit for my 103 build.

Whats the difference between Flat top Pistons and Dome topped, is this simply a compression thing?

Additionally, do Dome topped Pistons require head work for clearance reasons?
 
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Old 12-17-2017, 03:04 PM
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Generally, domes are for more compression. Flat tops are ideal configuration of combustion flame travel, too, especially in current wedge head combustion chambers. Ancient, true hemi head pistons (IE Ironhead Sportsters, Shovelheads) had huge domes to fill the combustion chamber and give decent compression ratios but benefited from dual spark plugs to light the fire on both sides of the dome, as flame travel "over" the dome was poor.
 
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Old 12-17-2017, 09:20 PM
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Assuming twincam.. It's a compression thing. if selected right the dome will fit. Wiseco domes should be no problem on a 103 providing the domes are meant for heads. Talk to wiseco customer service to be sure.
 
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Old 12-18-2017, 09:54 AM
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Agree with Max, by the way, if you happen to be looking for some 103 standard cylinders I’ve got some in the classifieds !
 
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Old 12-18-2017, 11:58 AM
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Originally Posted by robbyville View Post
Agree with Max, by the way, if you happen to be looking for some 103 standard cylinders Iíve got some in the classifieds !
would love to take advantage of a set of 103 jugs, but shipping cost alone to Switzerland would buy me a new pair here
 
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Old 12-18-2017, 04:57 PM
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Piston crown design is just beginning to show promise in the automotive circles. Harley may never get to the level of GM's Corvette LT1 design. But, it sure would be nice as I'd love a DI engined HD.
 
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Old 12-18-2017, 07:50 PM
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It's supposed to help with travel to get full skirted pistons as well.
 
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Old 12-18-2017, 09:07 PM
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Originally Posted by Jay Guild View Post
It's supposed to help with travel to get full skirted pistons as well.
Please explain.
 
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Old 12-18-2017, 11:07 PM
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A full skirted piston extends further down the cylinder and provides more resistance to the Piston pivoting on the pin. Less chance of warping rings and the Piston travels closer to parallel of the cylinder walls.
 
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Old 12-19-2017, 09:00 AM
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Originally Posted by Jay Guild View Post
A full skirted piston extends further down the cylinder and provides more resistance to the Piston pivoting on the pin. Less chance of warping rings and the Piston travels closer to parallel of the cylinder walls.
As far as I know skirts on narrow skirted pistons are the same length as full skirted ones unless the build is different (bore, stroke, rod length). You want resistance for the pivoting on the pin. It should float. I don't see how it would make any difference between the 2 piston types. Piston skirt, narrow or wide wears mainly on the thrust sides (front and back) where the skirts are located on a narrow skirt piston. The piston pin / rod keep the pistons from rocking where there isn't any skirt.

I have a 02 RKC (about 80K) with about 60K on a set of 95 ci 10.8 to 1 slipper skirt early wisecos. It's easily had 100 dyno pulls at various times, made as much as 110 hp, had ccps as high as 220 psi (depending on the cams) and been run hard at times even with temps over 100F. It hasn't blown up yet. Burns maybe 1/2 qt in 3000 miles.

I'm not worried.
 
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