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Hey guys I am looking into doing dome top end work on my '76 and was curious as to what the largest piston I can run in a 74" without boring the cases would be? trying to get the maximum performance while still being able to kick it over.
 

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Don't weaken the cylinders by punching them to the max, You will gain lots more power from compression than from the few cubes you achieve by punching cylinders. Bump the compression and choose the cam VERY WISELY ! The proper camshaft choice will bleed off enough compression through overlap to allow kick starting.
 

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Hey guys I am looking into doing dome top end work on my '76 and was curious as to what the largest piston I can run in a 74" without boring the cases would be? trying to get the maximum performance while still being able to kick it over.
almost NO performance difference even if you bored it to 3 1/2 inches and thats the 80 inch bore ( 74 inch = 3 .438 /// 80 inch = 3 . 500 - so .438 plus .060 = .498 the 80 inch bore not the stroke it has

BUT power comes from stroking the harley motor no amount of bore in the early motors will give the torque the bigger stroke will - usable combo stock 3 -31/32 stroke 74 inch - 80 inch is 4 1/4 stroke stock motor strokes

the combo we build for the bobbers that cross country ride -- 74 cases or 80 inch cases same exact motor combo - 4 1/2 stroke 3 .5 inch bore = 86 inches
use a long duration cam with .450 lift and it will run 25,000 miles and counting - mine lasted 25 years no idea miles i lived on it as a kid
 

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Clean the flashing up in your intake ports. Remover a little material all over but more on the roof. Leave intake track with a rough texture to help keep fuel atomized in air flow. Polish exhaust port but dont need to remove material. Shovels flow exhaust just fine so if you want more exhaust flow go with smaller baffels or less restriction. Dont run larger than 1 3/4" exhaust or gonna loose midrange and setting carb will become impossible. Compression ratio over 9.75:1 run dual plug heads because high dome shrouds flame propegation.
 
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