Flowing Heads

As I am getting closer to giving my bike the power lift that it needs, I am curious as to which numbers are more reliable. Are the numbers given from a flow bench that is utilizing a velocity stack more accurate? Or are the numbers that are given from using an intake manifold more accurate? How do they differ other than piece of equipment?

Been checking out VeeTwin Racing have you....In my uneducated opinion I would say a manifold would be more real world than a Velocity stack,unless maybe if you're running a Velocity stack off your intake ports

Emails off to you soon with answers to your questions my friend..

manifold ! the heads seem to start to back up on the intake side with the stack on the bench slap the manifold on there and at the same lift it flowed just right funny how the bench became happy when that happened !

So how inflated are the numbers from stack to manifold? Any idea?

mike carney was doing a set of heads for a good freind of his just last week . the guy he was doing them for. runs a certain class of 1000 cc sporter class for bonneville . first name is ken dont want to give his last name dont know if they can run ported heads any way . they were doing the porting and going back and forth to the bench as they worked on the floor of the port and trying diffrent valves to get the flow they wanted with the stack attached at the lift they were at no matter what they did the head would start to back up . they tried to change the shape of the port by adding clay and then flow again . just playing around with floor and roof and what not . when the removed the stack and put on the manifold that he would normally run . it stop backing up and they got the numbers to come right in by going back to the original port and valve that they started with .

p.s. some flow benches are much more happy and others are very sad , its just a tool for the porter just like a dyno to an engine builder . some are happy some are very sad .

Are you Happy or are you Sad??:roflmao::roflmao:

I understand. But now this begs the question. One can really only flow as much air as the intake will allow, so why would you want to use a VStack when the Vstack is bigger diameter than the manifold?? The manifold seems to the a bottle neck.

remember its not only the amount of air . it all about the speed i can get it in there . ! so the manifold was the taper it needed to actualy make it get there at the right time!

Hence the bigger valves ?

Thanks for the info BP...so the stack flowed too much air too fast to find the port shape they were looking for??

yes for what the porter was trying to do with the port and valve lift he was working with. they were going back words fighting them selves trying to get the head to work .. AND let me state that this is one of the best porters in the country in the automotive industry . he does all the port development for dart. weld tec. wilson. brodex you name it they digitize from his port and chamber development . there is not an engine masters competition that his heads and intake are not in the win top 10. there is not and intake and head combo that is not on a norteastern modified. car that is not on the top 10 . year after year . he does not deal with the public he does not have a web site . this guy just deals with engine builders . what im trying to get across here is that he stoped before he started digging . in the port and used the bench as a tool to educate him self on how to make the head flow . thats the diffrence of knowing what to do with the numbers . you dont just hand your heads over to the guy whos numbers are the best . you hand your heads over to the guy who gets the best numbers for the lift that you are working with . a head that makes great flow at 650 lift . will not flow as good or as fast as a head that has an opening 500.lift so you want the head porter to work the head to flow its best way before youre. at the nose of the cam . so the cylinder fill . is productive follow me ! thats what make great torque . you can have a huge intake valve and a huge exhaust valve . and make great torque up high in the rpm range . the fact is we have mules not rocket ship bikes . i want to wack the throttle and pull away from the rice burner at the lite i could give a rats ass he pulls me at a hundred . i want to roll the throttle and make 90 foot pounds of torque at 3000 grand . not at 6200. every time i put the harley on the dyno at my buddys shop . he just shakes his head and states its just amazing to me you guys with four valves and two cylinders make that kind of torque at low rpms . yes he has a Japanese bike shop !

if you look at the dyno sheet back when i posted the timing pulls when my bike was an 88 . at 22.5 hp i was allready making 67 foot pounds of torque . i think if im not mistaken that was at 2300. rpm . those were stock valves and ports with just the short turns and bowls cleaned up no reshapeing or hog work done .

A lot of the reason T-Man does stage 1,2,3,4 heads. Most people only need the stage 2 to make the most numbers for a street able longevity road bike. Don't have to be a rocket surgeon to understand air in, air out. It a compressor. Also remember inversion on a Harley engine, that's the dip you see on the chart at some stage of the rpm band. Don't know what it is, look it up.

That's why you find a good head man and let him do his JOB.
I ain't a machinest.

If he has proven heads and they put out good numbers, that is what I need to know.

I've seen CNC machines work and seen how much they cost.

S&S CNC Head Porting with Wally Cahill - Part 2 of 3 - YouTube

excellent video for explanation of how to digitize and flow heads card board

awesome...lend me about $2500 for some headwork.

Not being a smartazz Smarty but I think you meant cam/intake reversion....

Here a some approximate points where reversion stops and your bike is "on the cam"

30 degrees = 2400 rpm

35 degrees = 3000 rpm

40 degrees = 3600 rpm

45 degrees = 4000 rpm

50+ degrees = 4500 rpm

Excellent info BP...You do engines or something for a living??:roflmao:

if you need 2500.00 bucks for sovel head work we got big problems !!!!!! i can build the whole motor and do the heads . and that shovel will haul ass for less than that , gee wiz

But then what ya got to talk about. I spent 1000 on it for the WHOLE Build.:rant: