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OK, I have a 94 580 here, no raves. Contemplating a couple of things to make more power. I have to mod stuff or I am not happy LOL. I got a great deal on this engine, is why I didn;t just start with a 670. Basically, looking for good Mountian performance, and I like being different. This engine will be going into a S chassis, with REV seat, 144x2 track. and a bunch of other goodies.
I wana hear some input on what you Guru;s think

1) put Summit 583 jugs on, with Raves. Same bore but better porting and with raves. easier for pipes too.

2) Bore my cyls out 2mm, from 76 to 78, use 670 slugs. Make a 611. Should still be able to use 583 pipes, but will not have raves.

3) 583 jugs with Raves bored to 78mm with 670 slugs. If the cyls will take a 2mm overbore, this would be the best way I would think. It would have all the right port timings because the stroke is unchanged, but an even larger bore. I would think one would be able to turn some impressive RPM's?? large bore/short stroke.

4) slap a set of 670 jugs and slugs in. Now the 670 stroke is 70mm the 580 is 64. So, I would have to shave off 3mm from the bottom of the jugs to obtain the same TDC height. But the port timing will still have increased in crank degrees because the stroke is shorter. Would it be better to take the 3mm off the top, or 1.5 of each. Alot easier to take off the bottom. Maybe this isn't a viable apporach.
 
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