anyone getting 100" out of their bench?

[1960FL]

Obviously Larry you have never heard of the 80/20 rule I/E 80 percent of your sales come from 20% of your customers ETC…

You read and follow porting as you do it for a profession from time to time, if you read my post you will see that I say “My personal generality looks at it like this”

So what I am saying is that if you are not getting the 80% of the gains by testing at 28” and tuning; Jumping to testing at 100” isn’t going to solve your problems.

Just how much do you think your porting jobs would improve it your were testing at 100” ?


You have all the answers,

Lets here.

Rick

[jfholm]

I would like to input a little on this subject. As a rule 28" h2o should be good enough. There are cases when testing at a higher depression is beneficial. I read a thread by Larry Meaux on this very subject. He was doing some LS Chevy heads and looked great at 28" but they were down a little on HP. He then reflowed the heads at 36" on the intake and 42" on the exhaust. If I remember right, he found at 28" all the exhaust we the same, even flow and were smooth. When he flowed again at 42" then he had uneven and turbulent flow. He then corrected the heads at the higher flows and noticed a good increase in horsepower and performance on the track.

All heads do not act this way. Also what are you doing? Are you running for the record? Or do you just want a substantial gain without breaking the bank. Be realistic in your endeavors. Building a higher depression bench is just like racing. The more you want the higher the costs are on a logarithmic scale.

JMNSHO (just my not so humble opinion)

John

[larrycavan]

Obviously Larry you have never heard of the 80/20 rule I/E 80 percent of your sales come from 20% of your customers ETC…

You read and follow porting as you do it for a profession from time to time, if you read my post you will see that I say “My personal generality looks at it like this”

So what I am saying is that if you are not getting the 80% of the gains by testing at 28” and tuning; Jumping to testing at 100” isn’t going to solve your problems.

Just how much do you think your porting jobs would improve it your were testing at 100” ?


You have all the answers,

Lets here.

Rick

Well...actually NO. I never heard of that rule. But that's not what I read in your post or at least it wasn't what I interpreted your statement to mean.

It appeared to me you were talking about flow gains or knowledge related to them as the flow test pressure was increased. I asked where you came up with that linearity or rather non linearity in proportion of test pressure increase. Is that clearer now?

[larrycavan]

I just finished up a motor for a hill climb motorcycle. It's a pretty cool project and an area of competition I've never been involved with before. It's a 1428CC Kawasaki in a dirt bike frame.

When deciding on the combination of cams and porting for this engine, especially the porting, I spend a lot of time with the pitot tube in my hands and going back and forth from work bench to flow bench testing small changes to the short side radius. I had to make this thing flow the numbers with less CSA than I would normally use for an engine of this size.

I would loved to have been able to test it at 48" rather than 28".

This bike will compete in the Pro class against modern 4 valve motors. I need to make lots and lots and lots of torque and have it available immediately if the need arises to get off and back on the throttle.....whole new game here..

I spent some time on the phone with Larry Meaux last week discussing Pipe Max values, etc.

You're entitled to your opinion Rick and seeing as how this is an open forum, I'm entitled to as questions. If you don't like being questioned, that's your problem...not mine.

[jfholm]

That thing has a chain on the back tire doesn't it? That is cool. If only I was younger

[Malvin]

jfholm
That thing has a chain on the back tire

Looks like a nasty chain with spikes on it

[Tony]

Its for riding over people you don't like.

[larrycavan]

Let's talk real world instead of theoretical nonsense.

Once a head is baseline tested, the 80% gains generally come directly from establishing the correct cross sectional areas. It's that last 20% that the flowbench helps you to find. The closer you can duplicate dynamic conditions [which you'll never fully achieve with any flowbench] the better your chances of greater success.

A lot of that last 20% is about shapes. Get the right and good things can happen.

[jfholm]

Let's talk real world instead of theoretical nonsense.

Once a head is baseline tested, the 80% gains generally come directly from establishing the correct cross sectional areas. It's that last 20% that the flowbench helps you to find. The closer you can duplicate dynamic conditions [which you'll never fully achieve with any flowbench] the better your chances of greater success.

A lot of that last 20% is about shapes. Get the right and good things can happen.

Larry,
I agree with you. The first 80% or even 85% can be gained a lot of the time with just a good pocket port not even on the flow bench. That last 15 - 20% really takes some work. I have spent a lot of time on the flow bench and don't feel like I have gotten 100% out of the port. Maybe I have but there always seemed to be time or money constraints in the way. I wish I had more of both. I would never make it as a professional porter anymore. I used to have a bad attitude of "good enough for who it is for" to some extent. Now I am too much the other direction and seem to have developed OCD in my old age. Sometimes you just need to do your best and get it out the door. I think that is why you always seem to find more the next year.

I know a guy who ports and spends a lot of the customers money on that last little bit that may or may not make a difference. Would it not be more beneficial to maybe spend that money on some new fresh slicks of the latest design?

John

[larrycavan]

Let's talk real world instead of theoretical nonsense.

Once a head is baseline tested, the 80% gains generally come directly from establishing the correct cross sectional areas. It's that last 20% that the flowbench helps you to find. The closer you can duplicate dynamic conditions [which you'll never fully achieve with any flowbench] the better your chances of greater success.

A lot of that last 20% is about shapes. Get the right and good things can happen.

Larry,
I agree with you. The first 80% or even 85% can be gained a lot of the time with just a good pocket port not even on the flow bench. That last 15 - 20% really takes some work. I have spent a lot of time on the flow bench and don't feel like I have gotten 100% out of the port. Maybe I have but there always seemed to be time or money constraints in the way. I wish I had more of both. I would never make it as a professional porter anymore. I used to have a bad attitude of "good enough for who it is for" to some extent. Now I am too much the other direction and seem to have developed OCD in my old age. Sometimes you just need to do your best and get it out the door. I think that is why you always seem to find more the next year.

I know a guy who ports and spends a lot of the customers money on that last little bit that may or may not make a difference. Would it not be more beneficial to maybe spend that money on some new fresh slicks of the latest design?

John

BINGO.... I hear you on that one! Racers are probably the worst ones to get on the common sense track...

What I find is that it's pretty easy to make the head flow more than the engine is using! That is as it related to dyno numbers and pipemax. The Ve based on airflow alone is much higher than the Ve that correlates to the dyno numbers. Even more frustrating is the numbers I get back from guys are chassis dyno results. I have never been able to come up with a comfortable conversion number for chassis vs engine dyno comparisons.

Even more frustrating is comparing the common Dyno Jet Chassis dyno to a Superflow Chassis Dyno. The DJ always yields significantly [sometimes as much as 30HP more] than the DJ does for the same bike

I can take and engine I've done, not touch the head again, change cams and carburetors and completely change the characteristics of that engine. Time and again I hear people blame port size for bad results. While that can definitely be a factor, it's also within the realm of possibility that the cam / carb combination is incorrect.