[Judeyramone]

Christ almighty! It's St Patrick's day! Why the fuck are you guys sitting around discussing head porting instead of getting sick on cheap bad green beer?
Ten years ago, when I helped move my friend Patty move to Chicago, Vortex was a well known gay bar in the boystown neighborhood (clubmans anyone?).

I'm actually ashamed theat I'm sober enough to respond ot this. My wife's upstairs (naked?). Goodnight all.

 

[jbranson]

I'll break my usual rule and agree with Champ. Craig might remember this....I heard his bike one year at Beaver, after hearing it many times at other tracks. So I says...Craig..dang your bike sounds great, something sounds very "right" about it...reminds me of the sound that Cole's Guzzi makes. Sure enough Craig says to me...guess what, just had the cylinderhead done by the same guy that did Cole's Guzzi. Right then and there I knew who was going to do my next cylinderhead. And I did have Mike Rich do my cylinderhead...and the bike does run great and stays together and has that special something in the sound. Mike is a fanatic, flow benches, computers, the real deal, does very very nice work, nothing left to guesses or wive's tales, everything get's tested.
So...like Champ, I do believe that a properly modified and tuned cylinderhead does make a certain "right" sound. A sound that in my head just says "healthy", "strong". Don't know how else to describe it.
JohnnyB

 

[jbranson]

I'll break my usual rule and agree with Champ. Craig might remember this....I heard his bike one year at Beaver, after hearing it many times at other tracks. So I says...Craig..dang your bike sounds great, something sounds very "right" about it...reminds me of the sound that Cole's Guzzi makes. Sure enough Craig says to me...guess what, just had the cylinderhead done by the same guy that did Cole's Guzzi. Right then and there I knew who was going to do my next cylinderhead. And I did have Mike Rich do my cylinderhead...and the bike does run great and stays together and has that special something in the sound. Mike is a fanatic, flow benches, computers, the real deal, does very very nice work, nothing left to guesses or wive's tales, everything get's tested.
So...like Champ, I do believe that a properly modified and tuned cylinderhead does make a certain "right" sound. A sound that in my head just says "healthy", "strong". Don't know how else to describe it.
JohnnyB

 

[KeninIowa]

Let me take a quess at what you hear.

A good head porter spends a lot of time working on low valve lift numbers. When the valve just leaves the seat is when the port gets it's initial suck. Velocity starts there and is easier to maintain once it's started. When you get a properly done head it's crisp everywhere and you can hear that.

05 KX 250f
01 GSXR 750
75 GT 550
68 Chevelle

 

[KeninIowa]

Let me take a quess at what you hear.

A good head porter spends a lot of time working on low valve lift numbers. When the valve just leaves the seat is when the port gets it's initial suck. Velocity starts there and is easier to maintain once it's started. When you get a properly done head it's crisp everywhere and you can hear that.

05 KX 250f
01 GSXR 750
75 GT 550
68 Chevelle

 

[parks61]

like champ needs help. team "vtp" to the rescue. the idea used to be called "swirl" but that was likened to toilet flushes. so some salesman who got a few too many swirlies during adolescence coioned a psyche saving term. i'm with judyramone...after watching my guiness hurl rotate down the porcelin bus last night, i attended to my naked wife.
parks

 

[parks61]

like champ needs help. team "vtp" to the rescue. the idea used to be called "swirl" but that was likened to toilet flushes. so some salesman who got a few too many swirlies during adolescence coioned a psyche saving term. i'm with judyramone...after watching my guiness hurl rotate down the porcelin bus last night, i attended to my naked wife.
parks

 

[robertob]

Hey Rosko - I just did the ports on my 450 and I was a chicken because I didn't want to mess it up. I cut the head for 1mm OS intake valves and just blended them in as well as clean up the port and bowl area. Oh yeah, I cut down the valve guide boss to match the length of the Kibblewhite guides I used too. I've got two valves left over if you need them.

 

[jbranson]

Ratty, yeah..that's just the word I was looking for "crisp", a healthy kind of resonant intake and exhaust sound...not too sharp...not doggy...just right.

Parks...yep, back in the day it was all about "swirl polished" valves...in fact I still polish the valve heads with that pattern. And the valves supplied to me from Ferrea and Manley come with a swirl polish.

Robertob....just the same extent of the work I'll do myself. And if you have a small lathe, making the guides from Kibblewhite blanks is pretty easy...just take the old ones out and copy them.
JohnnyB

 

[n/a]

Interesting enough that with a good porting job and proper cam the exhaust is just as important. I run into megaphoneitist at a certain RPM. The key to keep it in the power range is to keep it above that curve. Took me awhile to figure it out and keep the Ducati in the rev range.

VORTEX BABY!!...or if your old school...swirl.

Champ

 

[jbranson]

I've noticed with a 2-1 system megaphone design is not nearly as critical as with a single. We once put a particular megaphone on Mary's little honda single....freakin thing become instantly unridable..would make scary power from about 10,000-12,000 rpm and absolutely nothing but a sputtering mess everywhere else. Changed the pipe design....smooth power in most places...decent top end but not nearly the power produced in the high revs as the first pipe.
JohnnyB

 

[parks61]

the harmonic thing has been used a lot with modern sportbike airbox designs. usually show up as a dead spot in the torque curve around the 40% point in the rev range with a corresponding up-bump around the peak power point. 2 stroke exhaust design has always been about trade-offs and compromises. high peak (exciting) 2 stroke power has usually coincided with "nobody's home" power in the rest of the range. honda mts and champ's ta being good examples...you just ride around the "problem". the harmonic gods giveth in one place and taketh away somewhere else. broad (boring) power seems to be the other "less desireable" option. don't know about 4 stroke port harmonics (dr. branson?) but maybe you guys should be playing with air boxes. velo-stacks look cooler but are they the hot set-up? though i'd hate to see johnny lankied all over an air box on his honda. maybe you could put 3 or 4 more gears in the tranny, put that zinger exhaust back on (probabley has a good vortex type path in there), and tell mary to keep it between 10 and 12 grand. at the expense of end-of-the-straight top speed, boring power is often the faster way around the track, at least for me. corner exits are much more fun (and safer too) that way. an exception is that phil turk dude who goes fast everywhere. damn. he's got good swirl.

parks

p.s. aaron, please confirm that you sent joe's wheel.

 

[jbranson]

Parks,
I've got a small piece of windows software I wrote that calculates the "Helmholtz" frequency for intake runners. Designed for four strokes. Aaron should be able to verify this....when he set his intake to the indicated length and dyno'd his bike at Pete T.'s, the indicated intake length was only 5mm off the ideal length as determined by the dyno.
Here's a screen shot of the simple single screen program. Don't anyone try to actually enter numbers....it's just an image you know.
JohnnyB

 

[joe c]

ross!!!!


parks, thats funny.



jc


aaron, send my wheel.

 

[jbranson]

Just out of curiosity, what length intakes are most of you 350 guys running?

My program says with:
175cc/cyl, 9.75:1 compression, 32mm intake/ports tuned for 9000 rpm
Should be around 8.64" inches from valve head to entry of carb.

165cc/cyl 9.17"

30mm carbs and 165cc, 8.06"

175cc/cyl and 34mm carbs 9.76"

Entry of carb would include velocity stacks...or more accurately probably about 75% of velocity stack length due to the increase ID of a stack.
JohnnyB