J-Madd Posted January 12, 2017 Report Share Posted January 12, 2017 What do you think about this exhaust port shape?I know almost nothing about how to port or exhaust port shape. But if the cut out in the middle actually allows the port to open that is now the beginning and end of the duration. Not the flat area. And that is when the sound wave exits. The actual charge may not exit at the same crank degree as the sound wave, I dunno. I think you want the entire charge to exit quickly and completely. It could also be a last microsecond attempt to stuff the return pulse from the pipe back into the cyl before the port is completely closed. I'd like to hear opinions from those who know why that port is funky as well. Quote Link to comment Share on other sites More sharing options...
camatv Posted January 12, 2017 Report Share Posted January 12, 2017 there is no amazing quality to that exhaust shape.. 1 Quote Link to comment Share on other sites More sharing options...
camatv Posted January 12, 2017 Report Share Posted January 12, 2017 in my opinion charging the transfers and the actual tunnel is what is holding them back that along with the simple single port exhaust.. with a non triple port they can be made to run really good and if done right still have a nice lower end midrange off the pipe Quote Link to comment Share on other sites More sharing options...
SlowMoe Posted January 12, 2017 Author Report Share Posted January 12, 2017 in my opinion charging the transfers and the actual tunnel is what is holding them back that along with the simple single port exhaust.. with a non triple port they can be made to run really good and if done right still have a nice lower end midrange off the pipe Am I wrong in assuming that large boysen ports help the transfers charge more effectively? Quote Link to comment Share on other sites More sharing options...
bigweav81 Posted January 12, 2017 Report Share Posted January 12, 2017 That exhaust port seems small. There's plenty of room to work off the sides there. That funky shaped roof doesn't seem benifical in any way. If you have really opened up your intake then you may wanna re shape that exhaust, and widen it. Again I'm by no means an expert. Just tinker my damn self. Sent from my SM-S820L using Tapatalk Quote Link to comment Share on other sites More sharing options...
registered user Posted January 13, 2017 Report Share Posted January 13, 2017 when you deal with cylinders this old your bound to see plenty of crazy ideas that people have tried over the years. ive seen intake bridges completely removed among other stuff even more strange than that Quote Link to comment Share on other sites More sharing options...
SlowMoe Posted January 13, 2017 Author Report Share Posted January 13, 2017 (edited) That exhaust port seems small. There's plenty of room to work off the sides there. That funky shaped roof doesn't seem benifical in any way. If you have really opened up your intake then you may wanna re shape that exhaust, and widen it. Again I'm by no means an expert. Just tinker my damn self. Sent from my SM-S820L using Tapatalk Yeah it does seem pretty conservative. If it were me I would widen it 1-2mm on each side, at the top, then taper it down to the current width at the bottom Edited January 13, 2017 by SlowMoe Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted January 13, 2017 Report Share Posted January 13, 2017 I use the tunnels as a funnel, with this theory I've seen engines that overrev much better and effectively pull gear past peak. I'm sure someone will disagree but this works for me . I've seen a ton of different porting styles and ridden all types. I've noticed engines with hogged out tunnels never really pull out the back door and fall flat way quicker than one of my engines. I'm guessing they went big enough they compromised port velocity Quote Link to comment Share on other sites More sharing options...
SlowMoe Posted January 13, 2017 Author Report Share Posted January 13, 2017 I use the tunnels as a funnel, with this theory I've seen engines that overrev much better and effectively pull gear past peak. I'm sure someone will disagree but this works for me . I've seen a ton of different porting styles and ridden all types. I've noticed engines with hogged out tunnels never really pull out the back door and fall flat way quicker than one of my engines. I'm guessing they went big enough they compromised port velocity So essentially you dont spend much time opening up the area near the windows, correct? I have done this once. All I did was raised the transfer roof and hogged out as much as i could reach from the entrance. And the exhaust port wasnt even big at all. And it revved like a mofo Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted January 13, 2017 Report Share Posted January 13, 2017 Not exactly, I work the windows and areas rite before also but knowing how much to take out comes with time behind the wheel. I like an engine to freight train. Quote Link to comment Share on other sites More sharing options...
registered user Posted January 13, 2017 Report Share Posted January 13, 2017 (edited) moe when your talking a 30hp engine, almost anything you do inside the cyl will give more power so don't pat yourself on the back to much LOL. read some more books. practice on a few junks cyl and don't ever get to big for your britches and think you have a halfway understanding whats going on inside there because its rather complex. a lot of it I don't understand and Ill admit it. about the funell affect, I believe theres a specific ratio, although I don't recall what it is, between the runner entrance and window, once you exceed this ratio the air speed no longer increases. example, you make the entrance 4x larger than the window, the airspeed may not be any more than if the entrance was only 1.5x larger than the window. so don't blindly hog out the runners. another thing is the mixture has mass, momentum etc. if you have your front and rear transers out of balance the rear charge can try to push the front one toward the exh before the spent gas is flushed from the comb chamber. this is especially a problem to watch out for if the rear trans aim directly across to the opposing side of the cylinder like stockers Edited January 13, 2017 by registered user Quote Link to comment Share on other sites More sharing options...
SlowMoe Posted January 13, 2017 Author Report Share Posted January 13, 2017 Well, I have read bell's book as well as the other one, back in the day, so I have at least a basic understanding lol. And when I cut transfers, I use that "pole" on a set of dial calipers to make sure they are the exact height Quote Link to comment Share on other sites More sharing options...
m671054 Posted January 13, 2017 Report Share Posted January 13, 2017 How do you duplicate the angles on the port roofs? Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted January 13, 2017 Report Share Posted January 13, 2017 Good question for RU, he might have a trick Quote Link to comment Share on other sites More sharing options...
stpltn Posted January 13, 2017 Report Share Posted January 13, 2017 Take a piece of soft solder. Mold it to the port you've finished. Transfer it to thick card stock. Transfer it to some thin metal and you now have a template to duplicate off of. Quote Link to comment Share on other sites More sharing options...
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