Crazylien Posted December 21, 2015 Share Posted December 21, 2015 Hello i was wondering if anyone ever has tryed something like this ? I'm planning some performance oil cooled engine build in the near future . first i was thinking about using my slabside 1054 cc cranckcase and placing a slabbie 750 gearbox in it since they are straight swap . still i want something with the old scool hi revving racer feeling and after doing some math i found out that even on "only" 14500 rpm a slab 1100 with a stroke of 58 mm had an average pistonspeed of over 28m/sec !!!! Not realy what i wanted to see . still if one would use second gen 750 shortstroke of 44.7 i'm coming out on an 21m/s for reaching my desired 900cc i would need a bore of 80mm to hit 898cc but i fear that the shortstroke setup will make it hard to properly feed the big bore , still it is kinda tempting to try if you see that on 16000 rpm it still only has an average pistonspeed of 23m/s . would it be possibel to properly feed this setup ? maybe with an third gen 1100cc head since they have bigger valves ??? my second option would be to use an long stroke 750 cranck , what would be my best option ? an slabside cranck or a third gen ? with a stroke of 48.7mm the pistonspeed still only is 25m/s and is would only need a bore of 78mm to reach 930cc i think this set-up whould be more easy to feed but i fear it would not have the desired racy feeling i'm looking for . if anyone has any ideas for me or some useful input or even ideas about what cranck of cyllinderhead whould be best or other things like what size of carburator . i would be thankful for anyone who shares his oiler experience with me . Quote Link to comment
kokolis Posted December 21, 2015 Share Posted December 21, 2015 I dont think that + 12k rpm is doable on theese engines not for long anyway, is not only piston speed but also their weight of the components, everything has to go lighter, it want be cheap and no way it will not granade its self on 14k Quote Link to comment
Oilyspanner Posted December 22, 2015 Share Posted December 22, 2015 Yep, Kokolis calls it right - there's a lot more to it than peak piston speeds . . . the stock 1100s rev limiter is at a true 10.8k, although it'll be indicating well over 11.5k, even the 750s didn't hit the high numbers on the tacho. The OC motor is a big strong motor and that's the thing, all it's internals are bigger than current high revving engines. Not mention the heat ! Good motors these old OC engines, but you need to play to their strengths, increase capacity and efficiency and you'll be okay. Quote Link to comment
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