SLORYDER

BTW anyone know the stock durations off hand?

And you sir are a Burt Reynolds imposter. I know he isn't this much of an asshole. And to sheefreak no sir I wasn't aware that those increased durations would yield that much more power. I, however would not feel comfortable hogging out the intaes on my own though. You are the man and I salute you for not being like the others on this forum who swing off the testes of the builders out here.

Re He He Heeeeee aaaallllly

Laying it on a little thick, aren't we? Let's cut the crap here. A stock banshee engine makes a certain amount of torque at a certain rpm . This rpm is determined by certain factors, the main ones being the tuned length of the exhaust pipe and the other being the port timing. Now Horsepower is torque times rpm. So if you have 50 lb of torque at say 3000 rpm, you wouldn't have bus say 25hp (numbers may be way off but the correlation is accurate". Now, if you can move that torque peak higher in the rpm range, say 6000 rpm, you would have effectively doubled the horsepower. Now you must keep in mind that generally the torque curve is shaped like a mound, as in if you are looking at a dyno plot with rpm on the horizontal axis and horsepower on the vertical axis. So basically the further you go away from the peak tq rpm in either direction, the less hp you will make. The reason a banshee engine has so much potential, it that it is able to rev to a very high rpm, and if you can get the torque "hump" to slide over to the right (on the dyno plot, of coure), to say, 9000 rpm instead of the like 7000 or whatever it is- even without actually increasing the amount of torque that the engine makes (increasing airflow through the engine) you can raise the amount of hp drtastically. This is what raising the transfer and exhaust ports do. It shifts the torque bump higher in the rpm range; this effectively increases total horsepower output and, at the same time reduces the amount of power down low. Now about the pipe, the other important part of the equation. The pipe also determines when the engine makes its peak power. How a pipe works: The exhaust pulse or pressure wave leaves the exhaust port and heads down the pipe. As it passes through the different diameters of the chamber, it caused the pressure inside the cylinder to fluctuate. This fluctuation actually "sucks" the rest of the exhaust out of the cylinder, pulls the fresh air/ fuel charge in, then pushes any fuel that may have escaped out the exhaust port back into the cylinder. (look at bansheemans sig). Anyway, the length of the pipe and its different diameters is what determines the peak hp rpm, as at that rpm the pulses going through the pipe reach a resonant, or harmonic frequency. Long story short, a pipe can be tuned to 6, 7, 8, or 10,000 rpm or more, depending on the purpose (trail-low, dune-medium-drag-high rpm tuning. So. you take a pipe that produced power at 10,000 rpm, shict the torque bump to peak at that same rpm and you will seriously bump the horsepower. Now, I realize that there's more to porting than just increasing the port timings, but there's a VERY significant amount of power to be had by raising the transfer and exhaust port windows IF yo know how much to move each one. My question, in a nutshell is if I slapped some shear pipes on my bike with the porting I have how many more hp could I expect from a drag port. Thanxx

So i'll be riding 50/50 drag and play riding. I've never ridden a shee with drag pipes, so I really don't know...but....how much more fun would the trail riding be with the pt pipes, I mean I'm not trying to win any medals at the drags but i want to be able to beat some of my buddy's cammed 450's and such...

Well, the opening is pretty close to oval, I probly coulda went a little more square on it. I guess I'm nervous because before I run the bike, I want to send off the whole motor to get inspected and rebuilt. I want the bike to be decent in the drags, but if i can keep my transfers where they are and bring the exhaust up to about a 195, and still be within 5 or 10 hp of a "drag" port with drag pipesI will run with it and save the 500 bucks on porting and 550 on pipes. So after you get the intake transfer and exhaust durations up to "drag spec", about how much more hp is extracted by playing with roof angles and such? Decisions decisions.

Well, the opening is pretty close to oval, I probly coulda went a little more square on it. So after you get the intake transfer and exhaust durations up to "drag spec", about how much more hp is extracted by playing with roof angles and such? I guess I'm nervous because before I run the bike, I want to send off the whole motor to get inspected and rebuilt. I want the bike to be decent in the drags, but if i can keep my transfers where they are and bring the exhaust up to about a 195, and still be within 5 or 10 hp of a "drag" port with drag pipesI will run with it and save the 500 bucks on porting and 550 on pipes. Decisions decisions.

Alright bretheren this is what I did. Cut the exhaust to 189 duration. Cut it to 68.9% of my bore dameter. Chamfered the port. I also opened up my intake and increased its duration a good bit, as well as widening the boost slightly. Next I shipped them to a reputable builder who raised my transfers a couple mm and verified that there were no other trouble areas with the layout and work I did. So. in a nutshell, I didn't just whip out a file and start hacking metal off my cylinders. I'm sorry if my previous write up exhibited some noobishness. And I've spoken to a builder and he said it would be roughly the same. So, I am still curious to know how much better it would run now compared to stock.

Ok, one more time. How much time did I save in the grand scheme of drag porting by cutting that much off my cylinders? And if we were talking in layman's terms, what would my porting be considered, if all I did was widen and raise my exhaust, and raise the transfers, leaving the angles the same?

Just curious I have a set and plan on getting some port work done

Ok my durations, ect. are in my sig. The reason I ask is I plan on having them drag ported and I was wondering how much more work I need done to them (40%, 75% more)because i'm sure it won't be full price if most of the work is done. Thanks

You can't tell what kind of port job it is without knowing the durations. However you can assume and i think you're probly right

Like the title says Thanks

UUUUUUUUUUUUUP

This

C'mon. You know you don't need those cylinders. Give' em up

Don't really care what brand thanks

Ok I'll try to upload some pics in a little while works dual rates 85 shipped Marvin shaw rear 100 shipped +8 swinger with chain 125 shipped 11 paddle ultra buffs small tear behind one paddle but has fresh tubes and held up well to a 10 mill cheetah 200 shipped

Can't reply to pms make me an offer on the shocks and the carbs I will get pics sometime tomorrow I am stil in the hospital

I can get some pics just not today my wifes about to give birth Ok roller with shaw out back and works dual rates out front plus 8 swinger includes chain bars all controls plastics and tripple buff 11 paddle haulers 900 stock bore jugs mid to upper port job with transfer work done by hjr includes pistons and head 250 shipped complete bottom end with clutches and trued welded crank by hjr 375 shipped 34mm pj carbs with billet intakes cable and pods 250 shipped Paul turner hi revs fatboy silencers have some minor dings but good working condition 250 shipped will separate some parts just lmk what you need and prices are pretty firm Thanks for looking

Just let me know what you have. Thanks

I went too far, eh

Oh ok But you do mean 27.2mm from deck to top of exh port right? And it should be a uniform taper from exhaust window to exhaust flange outlet, right? How much would you take out of the id of the flange outlet? I am at about 69% bore on my exhaust right now

Wait I'm confused. It is 27.2 mm from deck regardless of gaskets or what not right...

Sweet thanks.