screamingcub Posted March 13, 2009 Report Posted March 13, 2009 Can anybody tell me from experience? What is the power gain associated with matching the cases to the bottom of the transfer ports,on a set of cub cylinders? What rpm range is most affected? What is the HP gain? Torque gain? For consideration my setup is:421 cub, 35mm PWK's with K+N's, UPP Intakes, V3 Reeds, 19cc domes (110 octane), CPI SB inframes Quote
rubberneck Posted March 13, 2009 Report Posted March 13, 2009 No dyno time, no experience with and without. I matched mine when i built it. I was told it is good for 2-3 HP max so i did it. If you dont do it, there is a considerable lip right in the flow path , so it just made sense to do it. Quote
sleeper06 Posted March 13, 2009 Report Posted March 13, 2009 I wouldnt say it affects a certain range,its more all around flow and delivery of fuel into the transfers,its free horsepower,and very easy to do Quote
shanYE west Posted March 13, 2009 Report Posted March 13, 2009 I was told it is good for 2-3 HP max so i did it. If you dont do it, there is a considerable lip right in the flow path , so it just made sense to do it. Yep.. That! Quote
screamingcub Posted March 13, 2009 Author Report Posted March 13, 2009 No dyno time, no experience with and without. I matched mine when i built it. I was told it is good for 2-3 HP max so i did it. If you dont do it, there is a considerable lip right in the flow path , so it just made sense to do it. 2-3 hp, OK. When I split the cases, it's getting some love. I'll have no problem, matching the cases to the transfer ports, but how deep did you blend the case? Any pictures of your handy work? Quote
dajogejr Posted March 13, 2009 Report Posted March 13, 2009 I wouldn't split apart a good running motor just to do the mod. However... If it was being split for another reason, then go for it. On my 4 mil I took a base gasket, used a marker and drew the outline, then had at it with a dremel. You do not want a polished smooth surface, you want a smooth surface with a rough texture, if that makes sense... Quote
sheerider1026 Posted March 13, 2009 Report Posted March 13, 2009 i did my buddys when i had it apart. i haven't doen my cub motor YET.. but like dave said, its not worth tearing it dwn to just port match the cases.. next time i am in there for some reason i will cut it also.. here is a picture of my buddys that i cut.. its a sorry as picture but may help you. i did the same as dave, used the base gasket as a template, used a marker, then yanked out the ole dremel Quote
screamingcub Posted March 13, 2009 Author Report Posted March 13, 2009 I wouldn't split apart a good running motor just to do the mod. However... If it was being split for another reason, then go for it. On my 4 mil I took a base gasket, used a marker and drew the outline, then had at it with a dremel. You do not want a polished smooth surface, you want a smooth surface with a rough texture, if that makes sense... I know what you mean for the surface texture,and yes it was running great. Until I broke the crank! Quick word of advise to anyone reading this, DO NOT USE AN OFFSET FLY WHEEL KEY!!!!!! I've replaced the following because I tried to save a few dollars: strokercrank,flywheel,stator, plus the down time! I'll post pictures of the carnage later tonight. Quote
rubberneck Posted March 14, 2009 Report Posted March 14, 2009 The easiest way IMHO is not to use the gasket trick. Paint the gasket surface of the case with a magic marker or machinist dye. After it dries bolt the cylinder to the top case half with a couple of nuts, no gasket in place. Turn the whole thing upside down on the bench and use a curved scribe to mark it from below. You want one of the machinest scribes that has a straight point on one end and a hook on the other. You can reach down through the top case half from the bottom side and run the curved end of the scribe all along the cylinder to case junction. It will leave a nice exact replica of the shape of the cub cylinder on the gasket surface of the case. what i did was just grind the case out to this line and then blend it down to the radiused part of the case. dont take off anymore material than you need to smooth things out. The thing about the gasket trick is that the gasket (at least the one i had) was actually bigger in several areas than the cylinder, so in order to match the gasket you would have been opening up the cases more than you need. Quote
flotek Posted March 14, 2009 Report Posted March 14, 2009 I would add also you will want to match the base gaskets to the cylinders /monoblock ,it wont do any good to trim the cases ..only to have a gasket hanging way over blocking flow into your transfer area Quote
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