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Old 10-28-08, 03:49AM   #1
gtofreek
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Default Flow bench variations

You know something, as Gach has stated, most people base their head purchase primarily off of flow numbers. Head porters like Dan Barton have stated that a flow bench is just a tool and nothing more. That there is more to a good head than how much it flows. I agree with both of these men, because they are both right in what they say.

The reason I bring this all up is because yesterday, I had the rare opportunity to flow a head[in particular, the same port] that two other shops from around the country also flowed and I had their flow sheets that they gave to the customer. All tests were done at 28" of water. I will refer to and post flow numbers for each shop as shop A, shop B, and our shop C. We use a Superflow 600 bench. Shop A uses a Superflow of unknown series, and shop B uses another brand altogether. These are the results each bench reported. I will list numbers intake first and then ex. I.E. 200/150.

Shop A:_____________Shop B:________Shop C:
.100= 41/63__________66/56__________61/47
.200= 94/121_________126/113_______119/105
.300= 169/151________197/149_______186/139
.400= 238/181________264/178_______255/178
.500= 294/212________318/203_______311/206
.550= 313/220______________________328/216
.600= 328/231________340/221_______341/224
.700= 354/240________367/233_______360/234
.750=_______________ 374/237_______368/238
.800= 364/248________370/241_______371/241
.850=________________367/243_______354/
.900= 348/252

Shop A used no pipe on the ex. so this chart of our shop C is without a pipe also. Shop B did not specify whether or not a pipe was used, however, when I put a pipe on it the ex. more closely resembled Shop B's ex. numbers. Also, Shop B did the port and head work.

As you can see, there is a huge difference between bench's. This was the same port on the same head. Now, all three shops were selling this exact same set of heads and they advertised them with these numbers.
Shop A is asking $3500
Shop B is asking $3600
Shop C is asking $3550
If all you based your head purchase off of was flow numbers, which set of heads would you buy and why? Keep in mind, you have no idea they are all the same set of heads. This is the first time I have been able to make a comparison between three bench's and I find these numbers very interesting. One mans 374 is another mans 364. One mans 41 is another mans 66!

What I find interesting is two things:
1. Shop A had less flow on the intake than the ex. below .300 lift where shop B and C did not have the same finding. I'm sure it's not a typo because it was done in the computer with a head port flow program So I think all numbers would have been the same way.

2. The shop with the best flow numbers[and the shop that will make the sale of these heads] just happens to be the shop that ported them. Coincidence? I think not! But then again, read my signature!

Something else I noticed is we use a fairly stiff checking spring for the flow bench checking and at lifts of .250" and less, the suction on the valve was sufficient enough the suck the valve down ever so slightly. It did not pull the valve down off the micrometer but it did make turning the mike with the flow bench running significantly easier to turn then it was with the flow bench off. At any rate, if I just slightly lifted up on the valve retainer to hold it against the mike, it would make as much as a 5 cfm difference. If I steadied the flow bench right at 28", then let go of the retainer, I would lose a full inch of water as it dropped to 27". Lift up slightly on the retainer and it would go back up to 28". Basically, what I am saying is the strength of the spring used can make a fair amount of difference also. If you notice, the ex. numbers were a lot closer with each other than the intakes were. That makes me wonder if Shop B was using a very weak checking spring for their test. A really weak spring would explain their consistently higher numbers and why the ex. is closer than the intake.

At any rate, food for thought and I'm getting real tired. Just saying, don't put so much emphasis on flow numbers. They will vary.
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Last edited by gtofreek : 10-28-08 at 04:05AM.
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Old 10-28-08, 05:38AM   #2
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Good point about the springs.

Something I've done with my home Audie technologies setup is to use a stock unported duplicate head to fine tune my calibration, and actually compare flow increase over stock as opposed to just looking at the number that you get.

In other words, compared to a stock identical casting # head, I increased my cfm by 35 cfm on one set of heads I did on it, and 25 cfm increase on another set of heads I did.

But of course you don't always have a matching spare untouched head sitting around either.
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Old 10-28-08, 12:14PM   #3
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Quote:
Originally Posted by INJUNTOM View Post

In other words, compared to a stock identical casting # head, I increased my cfm by 35 cfm on one set of heads I did on it, and 25 cfm increase on another set of heads I did.
Thats exactly what these benches were intended to do, they were not intended to spew out magical numbers, guess some people have there manometer filled with kool aid
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Old 10-28-08, 06:21PM   #4
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Bore size make a difference to I've been told...Paul very interesting
test.
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Old 10-28-08, 07:27PM   #5
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Quote:
Shop A is asking $3500
Shop B is asking $3600
Shop C is asking $3550
If all you based your head purchase off of was flow numbers, which set of heads would you buy and why? Keep in mind, you have no idea they are all the same set of heads. This is the first time I have been able to make a comparison between three bench's and I find these numbers very interesting. One mans 374 is another mans 364. One mans 41 is another mans 66!
I don't think any of us would know..most of what we buy is from what that person reputation is, and that's the problem. You have no idea what
your getting. There's so many variable's that they can easily say..this is
off that is wrong and that's why your not running the numbers.

Over the past 10 years..I've probably had heads done by everyone
in the Pontiac coummnity..Butler...KRE..RRE and have had the opportunity
to flow one against the other on the same bench..same day. I figure that's how you learn..most of it came from helping/doing motors for friends
almost for free.

After seeing this..I won't buy heads from either of them again. The ports were totally inconsistent from port to port. The best set believe it or not
was RRE..they were suppose to be CNC ported..they weren't. At the time
I was doing two motors for friends...they were exactly the same combination carb to pan. But two totally different cars.

They both agreed to use both their sets of heads for the dyno test to see which heads were actually better. We dyno the motor with the only changes being made where the heads...KRE heads frist then swap to RRE heads..when we put on the RRE heads..it made 75 more HP!
We where blown away. They ague between the two of them which heads
was the better set of heads. Of course I knew because we flowed both heads
same day same bench.

But that motor was going in a back halve car and the RRE heads went
in a stock suspention car. The back halve car was my old car. He was running 10.30's with the motor I built..which was a 462 with ported R-Air
1V heads... they only flowed 265 cfm. It ran 10.30's with a Torker 1 intake and a two inch spacer to a dominator.

He went with KRE's whole top halve..Victor intake port match to there heads and the cam they pick. I think he spent a total of $4500.00 for every thing. it was suppose to be granteed to run 9.80's - 9.90's all he
wanted was to run in the 9's..wanted that 9 second time slip. The best
it would ever run is 10.10's...LOL So he pick up 2 tenths over the r-air
1V heads....LOL while others pick up 5 tenths over R-Air 1V heads

We heard every excuse in the book..the car had 4:56 gears...they said
nope...you need to go to a 4:10 gear...So I ran it though Perfomance Teands sim...I have both the Engine Dyno and Drag Race Dyno. What
it told me was with the gear change the car would lose 1 tenth...sure
enough it did. Then came more excuses...but finally Mike who was very interested in the out come..said hey lets put my head on..and see what
happens. My thorey it wasn't making enough power so it needed the 4:56
gear.

With out changing out the 4:10 we bolted Mike's heads on..frist pass
it went 10.00 the best past of the day was 9.80 I foget how much mph
it pick up...but I think it went from 126 mph to 132 mph..don't really
remember.

Get this KRE's head flow better the RRE heads..not by much..I think
10-15 cfm more...But RRE ports were with in 5% of each other..where
KRE were all over the place..some 20 cfm less then other ports. What
we did find though..the R-Air heads had a 62 cc chamber KRE's had
72 cc chamber.. So while they where off I had them cut down. I thought
to myself..well there's the problem.

We put them back on..and he pick up 1 full tenth..and ran a 10.00
so yeah I can agree with you and Dan..flow numbers aren't every thing.
But when I use flow numbers I'm asuming that the heads have good
ports. It's easy to see how they sell heads base on flow numbers. You
learn the hard way about flow numbers.
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Old 10-29-08, 12:27AM   #6
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As far as flow numbers go there are a lot of factors that should be considered flow alone gets you numbers period. We should be shopping for heads that fit with our application. My BBF had several options for same similar #s. The Kaase P51do heads best fit my intended goals for the least overall cost. My dealings with Kaase were great. I asked questions they answered. Told me flow numbers they advertise were conservative and would check out higher likely on anyone elses bench. They did that to avoid situation of someone calling up complaining they only got ?xyz# for flow. My heads actually did check out to flow slightly better, cant complain about that.

I agree on reputation being an important factor for buying. Unfortunately as reputation grows so does business. If the shop hires help to keep up with demand it puts qc at risk. Sort of a catch 22 situation. I tend to go for the smaller shops or at least a stable shop where you could trust anyone working there of doing a high quality job. Hard to find.

I found long ago that the "famous" shop didnt neccessarily mean it could do any better than someone without the hype. Often the lesser knowns are more than capable of meeting or exceeding the "famous" guys work, they just dont put out the hype.
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Old 10-29-08, 02:38AM   #7
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Bruce, that's exactly why for three years it was just Mr. Koerner and Myself. Early this year we finally found someone else that was good enough to be able to do the job the way we wanted it done. Like you said, it's hard to find good machinist's anymore that don't already have their own shop or a good job. It seems it is a dying art in some ways. There just isn't the amount of qualified machinists like there was 20 years ago.
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Old 10-29-08, 05:06AM   #8
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There isn't as many qualified anything anymore. Nobody gives a shit anymore, and don't want to put out the effort or pay their dues...
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Old 10-29-08, 10:31AM   #9
gtofreek
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Well said Tom!
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Old 10-29-08, 11:02PM   #10
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I found out something very interesting yesterday and today after playing with this head some more.

When I started, the valve had a 55 degree seat on it and very little backcut, really next to nothing. The paperwork said the seats were 55 degrees. I got the flow numbers I stated above. I made small changes to the port[mainly trying different throat angles in small amounts as there's not much there to work with anyway] and the low lift flow went up considerably[from 88 cfm at .150" lift to 111 cfm] from .300" and under. What I noticed is that since the low lift flow went up, the suck on the valve was considerably lower. On the test I posted above, I was loosing 1 full inch of water depression. After the low lift numbers went up, I was only loosing less than 1/2" of water. I had also back cut the valve to 40 degrees to acheive the results above as well as some minor throating. Today I was verifying the valve seat in the head and it turns out it is only 52 degrees but yet the valve was ground to 55 degrees. I refaced the valve to 52 degrees and retouched the 40 degree back cut and tried some different angles yet in the throat and now, by the end of the day, there was no pull on the valve at all! I lost no water on the manometer at all, and I'm using the same springs and titanium valve. I guess this makes sense since more flow is going through the seat gap leaving less to pull on the valve.

Just thought it was interesting so I passed it on.
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Old 10-30-08, 12:01AM   #11
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Poor workmenship...very interesting. I suspect allot of this goes out
the door...missed or just don't care. Thanks for sharing very interesting
in deed.
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Old 10-30-08, 02:11AM   #12
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Quote:
Originally Posted by gtofreek View Post
Today I was verifying the valve seat in the head and it turns out it is only 52 degrees but yet the valve was ground to 55 degrees.
Isn't that done on purpose at least some of the time?
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Old 10-30-08, 10:44AM   #13
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No, it isn't Tom. Sometimes they put an interference angle on them. For example a 45 degree valve seat and a 44 degree valve face. This way, when you have cylinder pressure pushing in on the center of the valve which in turns forces the valve face against the valve seat. With a 52 degree seat and a 55 degree face, you end up with a wedge opening at the exit of the valve seat. This wedge can allow carbon to build in between. Not good!
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Old 10-30-08, 08:47PM   #14
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Very interesting stuff there Paul. Even though I don't completely understand all the ins and outs of which you speak, good to hear/see actual results from a compotent machinist/builder! Thanks for sharing.

Employees that don't 'Give A $hit'? How can that be, I thought that it was just me being too picky..........that's what my Dad used to always tell me when I worked for him. I would fire somebody for half a$$ing a job, not showing up for work, ect., Dad would hire them back the next day.
That is when I decided to take the plunge and go it alone. I tried the 8 employee thing for a few years, with the combination of piss poor quality and the IRS robbing me, I decided to just do it all myself. That way, I KNOW when it is done, it is done right!

By the way Paul, when you get my $hit, every piece that you touch.........better have your signature on it! LOL. Just kidding, I know you'll do a 'Top Notch' job!

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Old 10-30-08, 09:42PM   #15
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Paul did you try a 45 degree seat from what I have seen it would help the low lift numbers the 50 and 55 degree seats help the top of the lift range I guess it depends what kind of combination you are trying to build. I have thought a lot about flow bench numbers and why some get totally different numbers.I think a lot of it is how particular the flow bench operator is building the port entrance radius. I think some people use radius plates that may or may not match the the port entrance. We use clay and build a approx 1/2 inch radius that matches the port entrance. Jeff can get repeatability within 1 or 2 cfm because he has done it so much.Then there are some people that their agenda doesn't match yours and they get completly screwed up numbers. Anyhow Paul good test very interesting.
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