[steve25]

Here are some pictures of what a bad set up can do to flow numbers at low lift .

I fellow came to me with his heads to reflow test his heads which whete tested at a shop in PA somewhere and he felt that something was not right.

In these photo's I am posting note that the dial indicator's shaft is not set on the same inclination angle that the valve is on this guy's 440 Mopar heads, in fact I set it up to be only 5 degrees off from being dead on to make the point.

Note how in my photo 3 my dial indicator on the top of the head is reading .050" of lift, yet the dial indicator I have set up on the chamber is reading .004" less and in photo 4 which is at .100" lift by the top side dial indicator, at the chamber side where still down that same .004" of lift.

Between valve lifts of .050" to .150" that is enough to make for a loss of air flow of between 10 to 15 cfm@28".

The point here is that many shops who do only Chevy or Ford stuff have bolt on valve openers that can't work right on a 14 degree Pontiac head, so whoever you take your heads to for flow testing make sure they can set it up right for reproducing accurate flow numbers, infact even a with good HD bolt on adjustable valve opener you can't get the set up dead on with out doing some mods to the thing!

[Half-Inch Stud]

Good info. My digital-read Gauge ha same mount interface. But that solid looking arm looks like an improvement over my bend-flat metal mount.

We need an efficient Gauge Mount design. Wonder what Spotts has been using?

[68azbird]

<deleted>

[Stan Weiss]

Originally Posted by steve25

Here are some pictures of what a bad set up can do to flow numbers at low lift .

I fellow came to me with his heads to reflow test his heads which whete tested at a shop in PA somewhere and he felt that something was not right.

In these photo's I am posting note that the dial indicator's shaft is not set on the same inclination angle that the valve is on this guy's 440 Mopar heads, in fact I set it up to be only 5 degrees off from being dead on to make the point.

Note how in my photo 3 my dial indicator on the top of the head is reading .050" of lift, yet the dial indicator I have set up on the chamber is reading .004" less and in photo 4 which is at .100" lift by the top side dial indicator, at the chamber side where still down that same .004" of lift.

Between valve lifts of .050" to .150" that is enough to make for a loss of air flow of between 10 to 15 cfm@28".

The point here is that many shops who do only Chevy or Ford stuff have bolt on valve openers that can't work right on a 14 degree Pontiac head, so whoever you take your heads to for flow testing make sure they can set it up right for reproducing accurate flow numbers, infact even a with good HD bolt on adjustable valve opener you can't get the set up dead on with out doing some mods to the thing!

Steve,
Most shops must have a way to handle 14 degree valve incline if they want to work on some of the LS stuff and high end BBC (14 degree) stuff.

Stan

[steve25]

68azbird I must admit I am really not sure how to take your comment here!

[steve25]

The potential problem is Stan that a lot of shops that can flow test have there "do that and this getter/ fluncky" do the flow check work that comes in and all too many times as with the guy who came to me the shop guy set up the head such that the valve can be opened with no concern about its contact angle in relation to the heads valve inclination angle.

[slowbird]

So how does this effect the engine?
All it is doing is effecting are the numbers written on a piece of paper.

[steve25]

Right, all it's doing is effecting the numbers on a sheet of paper, its the same thing when your degreeing your Cam and you dial indicator is not set for zero there's no effect from that being off I guess in your mind.

["QUICK-SILVER"]

Something is going on here that we havent been made aware of.

Just guessing I'd say flow test numbers were down compared to some other unknown information.

How to test wrong isn't answering the unkown question

Clay

[Skip Fix]

I would comparing numbers between benches you get more variance on bench calibration than a slight angle difference.

[Tom Vaught]

Originally Posted by 68azbird

<deleted>

Well I guess the Ford Motor Company really screwed up using Research Lab and in their purpose built Engineering Air Flow Labs.
What did they do with their Air flow info? They won FOUR Le Mans races against the best in the world. 1966, 1967, 1968, and 1969.

Another guy who "Knew Nothing" apparently named Smokey Yunick had a flow stand and he won a 'few" races in his lifetime. Not sure about snake oil in the 1990s but Harold Betties (formerly of Superflow and another company) seems to have a nice handle on flow testing. Harold is a personal friend. Smokey was a friend. My boss who won Le Mans 4 times was obviously my boss and a friend. RIP Mr Perry.

Sorry but I have to disagree with your post.

Tom V.

[pastry_chef]

Originally Posted by 68azbird

t
i can show you a 220 CFM HEAD that beat a 320 cfm head by a full second.
how can that be?
Especially funny when the so called Pontiac experts recommended the roller cam for the engine.

Post up the compete combination details!
There are many reasons why something like that **COULD** happen.

Unless port work was royally fubard either port flow number could run faster than 95% of street cars with correct combinations.

[mgarblik]

If you are shopping your heads all over town and having them flowed on different benches, the exact set-up used on each bench will have a slight effect on the flow number readings as Steve 25 illustrates. We have 2 Superflow 1020 benches at my school and a wet bench. They are calibrated once a month with verification plates. I also use the allot of the Brezenski fixtures Steve 25 pictures. You want to use a set-up that repeats every time so you can get % improvement. I don't really care much if my flow readings are not the same as some other shop down the road. I have never had an Edelbrock head for any brand of engine flow better than 95% of what they claim out of the box. Yet every AFR head I have had on the bench flows right at or a few CFM better than the manufacturer claims. What's up with that? I would think Edelbrock knows how to operate a flow bench. It's advertising and bragging rights I guess. Much like a dyno, it's just an expensive shop tool.

[Tom Vaught]

The flow number is just a flow number generated at a given test pressure:
1) Pete McCarthy's old Pontiac articles used 12 inches of water test pressure because that was all the bench he was using was capable of.

The basic Superflow 110 desktop bench could flow at 10 inches of water at couple of hundred cfm of flow.

The upgraded Superflow 300 bench could flow 400 cfm.

Then Superflow did the 600 CFM bench and about the same time the old Superflow 1200 bench. The first one of those large 1200 cfm carb benches was done for John Reed of Reed Camshafts. The 1200 bench used 16 vacuum motors to get the test pressure.
Smokey and Ford used very old air movers that were built like a tank.

The 1020 electronic benches make flow bench operation a lot easier.
That does not mean the people running the bench actually know anything about airflow (unless they had a class in that subject). They just know how to run a test.

Our expensive shop tool (at work) cost 3 million dollars. Totally automated.
Ability to control 4 valves at the same time during a test, vary the test pressures thru out the runs, store the data and print it out in graphic form. Test at pressures up to 67 inches of water test pressure at full valve lift.

So yes Mike, it can be a very expensive shop tool.

Tom V.

[steve25]

My point about the set up accuracy in relation to low lift flow and race power is this, a Cam at overlap can have the valves open anywhere from .080" with a good Hydro Cam to .250" lift with a full on race roller lobe.
In a well tuned race motor the Exh scavenging depression ( vacuum) is as high or many times it's even higher then the peak depression that the cylinder makes on the Intake stroke even at high rpm.

With both valves now open during overlap that Exh depression get back into the cylinder thru the open Exh valve and starts yanking the Intake flow into the cylinder well before the piston is even moving down on the Intake cycle.

In terms of making great top end hp and maybe even more importantly holding on to that peak number for as long as possible, David Vizard has determined that to do such Intake flow numbers @28" and at .200" lift should be a minimum of 150 cfm, with 145 cfm being ok and 155 cfm or better being great.

I hope with what I have explained here that this is what my concern is for getting accurate flow numbers from .050" lift to .300" lift.

[slowbird]

Originally Posted by steve25

My point about the set up accuracy in relation to low lift flow and race power is this, a Cam at overlap can have the valves open anywhere from .080" with a good Hydro Cam to .250" lift with a full on race roller lobe.
In a well tuned race motor the Exh scavenging depression ( vacuum) is as high or many times it's even higher then the peak depression that the cylinder makes on the Intake stroke even at high rpm.

With both valves now open during overlap that Exh depression get back into the cylinder thru the open Exh valve and starts yanking the Intake flow into the cylinder well before the piston is even moving down on the Intake cycle.

In terms of making great top end hp and maybe even more importantly holding on to that peak number for as long as possible, David Vizard has determined that to do such Intake flow numbers @28" and at .200" lift should be a minimum of 150 cfm, with 145 cfm being ok and 155 cfm or better being great.

I hope with what I have explained here that this is what my concern is for getting accurate flow numbers from .050" lift to .300" lift.

Since this is the street section i assume we're talking just street engines correct?

[steve25]

It can apply to any engine with headers that can create scavenging at the collector that is strong enough to get back to the Exh port of any cylinder that's at over lap.

Naturally we are also talking about open headers and also a merge type collector will produce a greater scavenging pulse.

[Tom Vaught]

When you get into ACTUAL Flow Bench Test Work and Research this gentleman is one of the best out there. LARRY MEAUX

Does not brag, does a great job with his heads, has software programs to help people do analysis work on a laptop. http://www.maxracesoftware.com/

UNDERSTANDS AIRFLOW (LIKE DAVID VIZARD) AND WILLING TO SHARE.

If you do call him, tell him Tom Vaught said hello. (Ford purchased his software and we used it as a comparison tool with our Research software.)

MEAUX RACING HEADS
9827 LA HWY 343
Abbeville, LA. 70510

[Formulajones]

I'm with Mgarblik. Flow benches are like dyno's, just depends on who is operating it. Find someone you trust with good equipment, and stick with them. Same equipment and same operator generally gets you comparable repeatable results that you can gauge progress off of.

[slowbird]

Originally Posted by steve25

It can apply to any engine with headers that can create scavenging at the collector that is strong enough to get back to the Exh port of any cylinder that's at over lap.

Naturally we are also talking about open headers and also a merge type collector will produce a greater scavenging pulse.

So just how much attention you think should be paid to .200 flow?
Say head A flows 120cfm@.200 and 400@.700 vs head B that flows 165@.200 and 360@.700.
Also at that low lift valve angles and valve size play a huge roll in the flow. Steep valve angles kill flow down there. But steep angles make power so ?????