Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties UL pistons

UL pistons

Post Thu Mar 23, 2006 7:31 pm

Posts: 104
Has anyone ever tried domed pistons (aka late KR ) in a UL engine?,just buttoned up my '40ULH and was debating this the other day. STROKER

Post Thu Mar 23, 2006 8:08 pm

Posts: 149
Location: calif
hi i have converted a small # of krs and 1 kh to dome pistons. pistons r very hard to come by. u probley would have to redo comb. chamber. not sure have never seen heads u r talking about. most my work krs xlrs xr 750. bore is 2.750 u can do heads in lathe on face plate. to make radi. could be done on mill. i did one set on mill lot more work. should do work in valve pocket area also. hope u best.

Post Thu Mar 23, 2006 8:46 pm

Posts: 1676
Location: Interlaken, NY USA

xlr, are you referring to the pistons and heads that they used on the very last KR's?? A buddy of mine has a set of those new old stock heads. Often wondered if they'd be good for any power boost on Frankenstein. Any thoughts on what the gain would be and where in the RPM range?

Post Thu Mar 23, 2006 9:28 pm

Posts: 149
Location: calif
yes 69r # be very carefull there was someone who took k heads and machined them a friend of mine bought a set off ebay. the real heads have 69r # cast on them. also pistons did also. helps mostley on top end. would hid barrells take k heads? also area above valves. that is very important for breathing. kr call for earley .110 for intake .040 exh. late .120 intake .080 exh. .040 piston to head. but i have run .035 what i mean {if i can type right} area behind valve in head needs to be concaved like radius. female type. kinda hard sometimes to explain typing { i am not to good at it} engine will run cooler also. gota make these flatheads run cool. thats kills lot of them. syn. oil helps. just no oil around head area like overhead to help cool. thanks

Post Fri Mar 24, 2006 2:15 pm

Posts: 919
Location: RENO,NV. U.S.A.
If you can find the specs (dimensions) for the late KR pistons,Venolia will make pistons for you,a little pricey;but they're forged pistons not cast. I had 2 sets made up a few years ago for the ULH ( which we just came back from DAYTONA on),16,000 plus miles so far on these pistons. Venolia supplied the pistons for the stage 2 XR 1000 engines. BREWSKI

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