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Thread: Looper exhaust porting
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11-26-2013, 12:20 PM #165000 RPM
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11-26-2013, 12:46 PM #17Scream And Fly VIP
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.150 wider on each exhaust port at the top, make sure you radius them when finished. Clean up the rod slot and match the intakes being careful to maintain original angle since you are not looking for a high rpm engine.
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11-26-2013, 12:57 PM #185000 RPM
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Just starting a v4 looper for a 15' allison,
Any thing different on the V4 ?
Will the V8 Finger ported piston w/ block mods work ok in the V4, or is there a better direction ?Last edited by thornl01; 11-26-2013 at 01:02 PM. Reason: spell
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11-26-2013, 01:00 PM #195000 RPM
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What needs to be done to the roof angle of the intake ports for higher rpm?
1975 Hydrostream Ventura II
1987 evinrude 200xp
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11-26-2013, 01:40 PM #20
4mm for each window...
have started matchporting transfer and boostports aswell, pics will be coming soon.
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11-26-2013, 01:44 PM #21
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11-26-2013, 04:25 PM #22
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11-26-2013, 08:41 PM #237000 RPM
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11-26-2013, 11:45 PM #247000 RPM
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.03937 is plenty accurate for almost anything done in a machine shop. Especially since there are a couple of zeros after the 7.
And 25.4 is more than OK, it is the absolute definition of millimeters per inch and provides a perfect conversion.
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11-26-2013, 11:58 PM #256000 RPM
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Heres a good conversion spreadsheet I use at work a lot.
http://www.elivermore.com/bills_conversions.xls
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11-27-2013, 12:16 AM #266000 RPM
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39.37 inches per meter was the old accepted standard until the late 1950's. 25.4 mm per inch is the current standard for conversion. In any case there is only .0002% difference between the two standards.
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11-27-2013, 09:35 AM #27
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11-27-2013, 12:56 PM #28Scream And Fly VIP
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You need an angle head to do the roofs of the transfers.
Higher rpm you the roof angle gets closer to 90 degrees and transfer/boost/finger port heights change a bit
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11-27-2013, 04:43 PM #29
Clean up the rod slot...
on small high revving case-fed motors, I have ported/created a "direct passage" from the crankcase(rodslot)to the transfer boost/aux-port, this procedure has been succesful by allowing the fresh charge to enter direct into the boostport as soon as the piston starts its upgoing movement.
Do you have any experience of this on outboards? In this case the boost port don't have to rely on the piston-window...
The yellow tape in the pic is an attempt to describe my idea
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11-27-2013, 05:13 PM #305000 RPM
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Fingerports or not ?