Flow bench guys, question??

[Blown 472]

When you are flowing a head, do you use vacuum and pull thru the chamber or how is the flow done and measured.

[Hotcrusader76]

On a Superflow it's normally pulled through the bottom. Dependant on the type of bench, 600 or 1200 series you can only pull one chamber or port at a time.
Hope that helps.

[Blown 472]

So you are pulling thru the exhaust port via the chamber??

[Hotcrusader76]

Well it depends on the bench. The 1020 series for example has a switch the can change the flow path in order to check the different measures.
I have become well versed in the theory of operation of these benches thanks to Superflow's staff in Colorado. We are purchasing one of their machines this year for the shop and dyno next Spring. We are opt'ing for the model which can do head flow at an efficent rate as well.

[Blown 472]

A switch to pressurize the chamber??

[Hotcrusader76]

Let me explain this a little slower...
You mount the head on the bench. The chamber is mounted directly above the benches flow port. Now to test the exhaust you can switch the flow path to exit the exhaust port of the head vice pull it through as you would the intake.
Does that help. :D
The bench is adjustable to different test pressures (H20)

[Blown 472]

I understand how it mounts, I was just wondering if the the flow was just taken by pulling thru the exhaust port/valve into the combustion chamber. But since you can reverse flow then you would be forcing air out the exhaust port via the combustion chamber. Thanks.

[Hotcrusader76]

Right. Since velocity can sometimes be measured dependant on the bench type it's important to have the right path of flow.
To flow a set of heads can be quite lengthy in time when your back and forth with porting and flowing, but that's where the money is spent.
Glad I could have been of some help.
BTW- my slugs will be on Ebay soon. Hhaaa

[Tinkerer]

They draw through the intake and blow out the exhaust. The airflow has to go in the normal way it will flow on an engine or the numbers will mean nothing.

[78Eliminator]

Smokey Yunick wrote an interesting section on this in "Power Secrets". Sure, you can take a head, hook it to a flow machine and get your numbers, but the BEST way is to use a machine that you actually attach to the shortblock. With the pistons removed, a huge vaccum hose is attached to a retrofitted oil pan (with no oil of course : ) ) and the other hose is attached to the carb inlet with the butterflys wide open. This way, each valve can be opened the the exact size of that the cam will and the heads can be measured and adjusted for REAL WORLD calibration rather than just looking pretty on a piece of paper. To do the exhaust, you just switch the outlet hose to the header. If you just flow a head and bolt it to you setup, it's shit all over. Yeah, to flow a head and get all the journals euqivalent sounds good on paper. But why? Each journal and path is a different length and the fuel mixture makes differnt bends as it travels through the intake manifiold and through the valves. If you think you are smart enough to "eyeball it" or even improve on the the existing design by taking a die grinder to modify the characteristics of your head, you are dead wrong. And to do this JUST by measuring the head alone? This is so subjective, it's snake oil. Leave this to the pros with the REAL flow dynos and not some dipshit who doesn't understand the ENTIRE PICTURE. Most of these guys are old and gray and have been though the racing circuits, like Smokey. Most heads are bolt on with little clean up, especially with forced induction application.
J

[Blown 472]

78Eliminator:
Smokey Yunick wrote an interesting section on this in "Power Secrets". Sure, you can take a head, hook it to a flow machine and get your numbers, but the BEST way is to use a machine that you actually attach to the shortblock. With the pistons removed, a huge vaccum hose is attached to a retrofitted oil pan (with no oil of course : ) ) and the other hose is attached to the carb inlet with the butterflys wide open. This way, each valve can be opened the the exact size of that the cam will and the heads can be measured and adjusted for REAL WORLD calibration rather than just looking pretty on a piece of paper. To do the exhaust, you just switch the outlet hose to the header. If you just flow a head and bolt it to you setup, it's shit all over. Yeah, to flow a head and get all the journals euqivalent sounds good on paper. But why? Each journal and path is a different length and the fuel mixture makes differnt bends as it travels through the intake manifiold and through the valves. If you think you are smart enough to "eyeball it" or even improve on the the existing design by taking a die grinder to modify the characteristics of your head, you are dead wrong. And to do this JUST by measuring the head alone? This is so subjective, it's snake oil. Leave this to the pros with the REAL flow dynos and not some dipshit who doesn't understand the ENTIRE PICTURE. Most of these guys are old and gray and have been though the racing circuits, like Smokey. Most heads are bolt on with little clean up, especially with forced induction application.
J Ding, you are dead on. The reason I ask this question is I was over at the Rock and Roll engineering site and he is making some hugh power in 472 cubic inch motors using a 1.66 exhaust valve, which lead me the question of the flow bench, I read somewhere that Smokey used to make exhaust valves smaller due to the surface area of the valve and the exhaust having to go around it to get out. To which a bigger exhaust valve being flowed or pulled thru the chamber via the port will put up a big flow number. Thanks for all the input, 78 I just ordered that book and looking forward to reading it. The guy that owns Rock and Roll engineering is a hugh Smokey fan and must have been a good study in his theroy.

[78Eliminator]

Blown 472:
Ding, you are dead on. The reason I ask this question is I was over at the Rock and Roll engineering site and he is making some hugh power in 472 cubic inch motors using a 1.66 exhaust valve, which lead me the question of the flow bench, I read somewhere that Smokey used to make exhaust valves smaller due to the surface area of the valve and the exhaust having to go around it to get out. To which a bigger exhaust valve being flowed or pulled thru the chamber via the port will put up a big flow number. Thanks for all the input, 78 I just ordered that book and looking forward to reading it. The guy that owns Rock and Roll engineering is a hugh Smokey fan and must have been a good study in his theroy. That book is the single best engine theory book I have ever read. His no bullshit attitude and simple explanations to complex questions are really enlightening. You'll enjoy this book immensly.

[058]

I'm also an SOS [student of Smokey] I like his common sense approch to engine building which is not so common anymore. I think one of the biggest reasons a smaller valve works is less shrouding around the combustion chamber allowing the full 360deg of flow. Big valves can hurt performance if they are so close to the wall that it hinders flow and creates turbulance. Too many people put too much faith in flow benches and the numbers they produce, thinking that more flow is always better, Don't get me wrong, flow benches have their place in compairing flow between ports and and valve lifts but it should be used for compairison and information only, not for maximizing total flow at maximum valve lift. Unless you are using a wet flow bench with the complete intake/exhaust tract installed then all the info is for compairson only and does not truly reflect what is accually flowing thru the port. Blown 472, can you get more info on what Rock&Roll Enger. is doing to get the numbers they are or perhaps you can post their website URL. Thanks, Bob

[Froggystyle]

I think this line is half right.
A flow bench in my experience is used to optimize the consistency from port to port.
To say that you cannot just get in there with a die grinder is ridiculous. I know a lot of people who have done just that to amazing results. It is in another recent thread here in fact where someone went in, unshrouded the valve, cleaned up the intake, gasket matched and blended a little and saw a huge seat of the pants increase in performance.
I would say that the guru's could get more out of it, and more consistently, but this guys spent some hours and a 30 dollars in grinding stones. Done! Big increase.
I have never had Smokey do my heads, but I have done my own and lost 1/2 second at the drags with no other mods.

[Blown 472]

058:
I'm also an SOS [student of Smokey] I like his common sense approch to engine building which is not so common anymore. I think one of the biggest reasons a smaller valve works is less shrouding around the combustion chamber allowing the full 360deg of flow. Big valves can hurt performance if they are so close to the wall that it hinders flow and creates turbulance. Too many people put too much faith in flow benches and the numbers they produce, thinking that more flow is always better, Don't get me wrong, flow benches have their place in compairing flow between ports and and valve lifts but it should be used for compairison and information only, not for maximizing total flow at maximum valve lift. Unless you are using a wet flow bench with the complete intake/exhaust tract installed then all the info is for compairson only and does not truly reflect what is accually flowing thru the port. Blown 472, can you get more info on what Rock&Roll Enger. is doing to get the numbers they are or perhaps you can post their website URL. Thanks, Bob Here you go.
web page (http://www.pontiacpower.com/index.html)
[ March 18, 2003, 01:46 PM: Message edited by: Blown 472 ]

[058]

Thank ya kindly, Blown