Big journal - cross drilling is beneficial.
Wedge it too... get as much counterweight off it as u can.
Speak to an engine builder (or resident Drmini) about it for more detail
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| Cross drilled cranks....any good... 1275s crank [poll] https://www.ausmini.com/forums/viewtopic.php?f=2&t=26917 |
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| Author: | volkmini [ Thu Jan 18, 2007 7:32 pm ] |
| Post subject: | Cross drilled cranks....any good... 1275s crank [poll] |
hi, i have a crossdrilled and polished crank and i'm woundering if i should keep the crank or trade it in for a standard one. are they many problems with the cross drilled cranks. thanks 1100s (1275) engine and parts thanks |
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| Author: | willy [ Thu Jan 18, 2007 7:35 pm ] |
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Big journal - cross drilling is beneficial. Wedge it too... get as much counterweight off it as u can. Speak to an engine builder (or resident Drmini) about it for more detail
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| Author: | drmini in aust [ Thu Jan 18, 2007 7:51 pm ] |
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Most small journal Morris 1100S (1275) cranks were crossdrilled and tufftrided. The big journal Morris 1100S (1275) ones are not crossdrilled OR hardened at all. For a road car that won't see past 7000 rpm, I don't think crank really needs crossdrilling. But there are a few schools of thought on this. 
What are the numbers on it- the small journal ones are pretty bulletproof, they are generally same as a Mk2 S except centre main width. If it's one of these I'd keep it. 
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| Author: | volkmini [ Thu Jan 18, 2007 7:53 pm ] |
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thanks for the reply. so what rpm do u recon i can get out of a 1360 with RE 13 cam and moded head |
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| Author: | miniobsessed [ Thu Jan 18, 2007 7:53 pm ] |
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well if the crank is in reasonable nick... you may as well keep it... why 'trade down' to a standard drilled crank... a cross drilled crank is meant to reduce the radius of gyration for the oil so it doesn't draw too quickly from the mains and ruin bearings... although this is apparently only really benificial in engines running about 7000RPM... and yeah... get it wedged! then lighten your flywheel and backing plate... then have the whole lot balanced  sweet
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| Author: | volkmini [ Thu Jan 18, 2007 7:59 pm ] |
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thanks...but what rpm will i expect |
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| Author: | drmini in aust [ Thu Jan 18, 2007 8:07 pm ] |
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My 1360 runs to 8K, it has a crossdrilled Mk1 S crank. Cam is an RE282 (prototype). I used to wind my 1310 to 8K on track days too, with an RE13 cam in. But really, over 7500 you are just reducing engine life, max power with even a race cam in a 1275 will be at 7200, no more. Max power peak with an RE13 will be at 6500 max, maybe less- depending on what else is in motor build. Remember too, all these `good' s/h cranks are now 35+ years old...
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| Author: | Lillee [ Thu Jan 18, 2007 10:05 pm ] |
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I don't care how big your head is, when you are running an RE13 it will peak about 6000-6500rpm. I have a PRETTY BIG head, carb, exhaust, intake, and will not rev it past this. Anymore and you are reducing your engine life for no gain other than sadistically throwing away money into an engine by reducing it's life. IMO the small J crossdrilled 1100S cranks are the bees knees |
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