trickedcarbine Posted May 27, 2011 Report Share Posted May 27, 2011 (edited) Ok, I have always been a high compression guy when it comes to my banshee, but lately it seems to be a major controversey. Obviously high compression motors are harder on parts and require high dollar fuel or alky to run and neither of that is a problem to me, because you gotta pay big to play big. On that note, well worth it. however I run a weird big bore stock cylinder and it actually destroys domes due to the lack of structural material on the sealing lip area. A major concern for Dave at NOSS. Any way, my builder and I discussed the idea of going with a machined stock head and with my current bore size and stroker crank it is probably the best way to go without giving wicked a call for their big bore head. Upon setting up the head, I mentioned how much I love the way high compression motors run down low. he proceeded to tell me that once you get it in to the revs you actually begin to lose power due to cranking loss. more or less the motor actually begins to fight it self. So rather then my usual 185 psi target I stated maybe we should take it down to about 165 psi to keep it reliable as well as see if it makes a little more horse power with out sacrificing some of that much desired torque. The day I go to pick up the head up he tells me that his math with a .020 base gasket and .020 head gasket puts me at around 140-150 psi and about 50-60 thousandths on the squish. Of course he saw my shitty look that I gave him and told me that it will undoubtedly run better then my last set of domes did, but if I wasnt happy with it he would cut it again for free. Am I nuts for being adamant about high compression and racegas motors? Where is the cut off point at wich the compression can actually cost power, granted the fuel is adequate and tuning is on target? I just don't get how most of the faster machines wether it is a car or bike run race fuel, but apparently it may not be the optimal set up. Is race gas just hype....... or a gimmick? Hypothetically, you take a Serval cylinder that is cranking at 150 psi and it lays down 50 ft. lbs. and 80 h.p. Would that motor make more torque at 175psi, but lose top end h.p.? I have just always been a firm believer in the compression being the way to go if you didn't mind breaking parts and high fuel prices, but now I don't really know what to think. Any one with a little knowledge or experience feel like sheding light on the situation? Edited May 27, 2011 by trickedcarbine Quote Link to comment Share on other sites More sharing options...
Coupelx Posted May 27, 2011 Report Share Posted May 27, 2011 I dont know the technical stuff but this time around i built a pump gas engine and have been way happier with it, not to mention cheaper to ride. Its alot smoother. Quote Link to comment Share on other sites More sharing options...
278 Posted May 28, 2011 Report Share Posted May 28, 2011 Reliability and smothness a pump gas motor is the way to go. I know there has to be a point at which your motor reaches a flat line as far as compression. I havnt done a lot of research into it but I highly doubt that 185 is that flat line I have seen guys go as high as 210 with a banshee motor(especially for drag racing) and I want to say I have even seen some higher than that. I dont know what you do with your bike(as far as riding) but there some guys on here that run alky with high compression on there duners and love it. Ive seen it on a few trail bikes, but I wouldnt recomend it for trail use. It definitely is a popular thing with the drag guys. Idk who your builder is but I would call around to some of the other reputable builders that are on the forum and talk to them and see if your guy is just not wanting to fix his mistake because like I said I dont think at 185 your flat line as far as power, especially since drag bikes are build for top end, and alot of he guys on here run high compression drag bikes Quote Link to comment Share on other sites More sharing options...
camatv Posted May 31, 2011 Report Share Posted May 31, 2011 high rev drag engines i try to hit aroound 155-165ish comp and run them on alky.. trail motors i have done as high as 210 and they live and run fine usually have No issues with damaging domes or breaking parts. but they are well built motors.. some larger drag motors dont rev all that high. 10k rpm is about the limit so they can run the higher comp ( or lower comp and increase timing HINT ) i think every builder can and will have a lil differnt setup. it would be intersting to see what that "special" cut head does. i have been liking alky as a fuel and replacement for 110 more and more these last few years.. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted June 1, 2011 Author Report Share Posted June 1, 2011 Thanks for the solid info cam. I would love to run alky, but I ride to much in the winter to wanna deal with the kick and spray, kick and spray ordeal. So, those cookies from the dark side. They aren't made by the same folks who made that really KILLER koolaid for Jones Town are they? Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted June 2, 2011 Report Share Posted June 2, 2011 Wouldn't the effectiveness of the pipe come into play at some point? IE, if you make say 185 lbs with a compression gauge, what kind of pressure is developed at 9500 rpm ? Quote Link to comment Share on other sites More sharing options...
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