Cylinder head flow
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71,858 Posts
Don't get hyped up on flow numbers.
Port speed and efficiency is where the power is made.
Years ago, the boys at Reher & Morrison along with, at the time one of the great cylinder head guys Lee Shepherd, took CFM away from the head and the engine responded with more power.
Port speed and efficiency is where the power is made.
Years ago, the boys at Reher & Morrison along with, at the time one of the great cylinder head guys Lee Shepherd, took CFM away from the head and the engine responded with more power.
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6,633 Posts
You want a head with the correct cross sectional area and correct airspeed through the port to match your engine displacement , intended RPM range, and use. While it's used to compare different heads, flow by itself is not what you want to use to compare a GOOD head. How high will you turn it? What intake will you use and will it be matched for the heads you buy? 1 carb, 2 carbs, or efi, and how much nitrous?
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4,798 Posts
I'd say the same thing, look at cross sectional area etc,
these days with some of the castings we have available design has more
then over shadowed the callenge to get cfm.
Flow numbers are aslo hard to compare cause there's no standard
for flowbench claibration being use, ..
therefore 460cfm on one's bench could be 435 on another.
Curtis
these days with some of the castings we have available design has more
then over shadowed the callenge to get cfm.
Flow numbers are aslo hard to compare cause there's no standard
for flowbench claibration being use, ..
therefore 460cfm on one's bench could be 435 on another.
Curtis
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1,781 Posts
I agree 100%. You need to get with the engine/head builder, and go over all the details. You could have 2 sets of heads that have the same flow, on the same motor, and 1 set can out power the other!
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90,869 Posts
I agree with Horndog, who would have guessed? I cite that Reher Morrision test all the time. They took 30CFM off flow and boosted power.
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4,045 Posts
Blue thunder 4.3s go about 440 cfm. i think that is all you are going to get out of that bore size. The next best thing is a Yates D3, or SC1 head, those go about 425-430cfm. I agree you will want extra cross section for a nitrous engine, probably 3.3 sq" being the minimum.
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8,149 Posts
Very true but if you look at what one guy's heads continously, make you have an idea which ones are bit inflated and which ones are more close to the performance. And I mean I would say that each head porter probally sets his bench up consistantly. But just my thought from reading and paying attention to you and others. Curtis do you use a 600 700 or superflow 1020? And do you use any pipe on the exhuast? Also anything on the intake side to create realistic no.s just curious?
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4,798 Posts
My bench has been calibrated with sharp edge orifice plates to the American Society of Mechanical Engineers MFC-3M-2004 national standard.
I also reference SAE J228 Airflow Reference Standards
It's the standard used by engineers world wide, ..
To me, it's important to have a "true" CFM number from my bench because of all the
other calculations I use to design heads, .. mass airflow, cfm demand, cfm per Hp airspeed, etc,
So I totally re-calibrated my bench from when I got it, ..
It would be easy for everyone to calibrate to the same standards, .. but most don't worry about it
as long as the bench repeats. So really most of us use a bench as our own little yard stick to measure improvements. The problem is consumers use it to judge
what head is better, and unless all of the benches are calibrated the same and the test methods all the same, they don't really compare.
I do NOT use a pipe for my published exhaust port numbers but I do test with
them VERY often.
On the intake I have radius plates etc that I use that are fairly consistent, .. a few
manifolds that are my test standards, .. and some fabricated "runners" , ..
it all depends on what I'm testing for.
I have a Saenz 600 bench that probably compares mostly to a 1020, .. it's more
conservative then most commercial bench calibrations.
Curtis
I also reference SAE J228 Airflow Reference Standards
It's the standard used by engineers world wide, ..
To me, it's important to have a "true" CFM number from my bench because of all the
other calculations I use to design heads, .. mass airflow, cfm demand, cfm per Hp airspeed, etc,
So I totally re-calibrated my bench from when I got it, ..
It would be easy for everyone to calibrate to the same standards, .. but most don't worry about it
as long as the bench repeats. So really most of us use a bench as our own little yard stick to measure improvements. The problem is consumers use it to judge
what head is better, and unless all of the benches are calibrated the same and the test methods all the same, they don't really compare.
I do NOT use a pipe for my published exhaust port numbers but I do test with
them VERY often.
On the intake I have radius plates etc that I use that are fairly consistent, .. a few
manifolds that are my test standards, .. and some fabricated "runners" , ..
it all depends on what I'm testing for.
I have a Saenz 600 bench that probably compares mostly to a 1020, .. it's more
conservative then most commercial bench calibrations.
Curtis
Thanks for the info guys..Guess I should have included a little more info on why I was inquiring. I have been looking into a set of Don Lassitos ultrapro billet heads. They have huge flow numbers all the way through the curve. I have no idea of cross sectional area, but if theses heads did have ports conuducive to high velocity, high flow would they still be much for the cubic inches I want to run them on..450+ inch windsor, 2 foggers, max effort, small tire deal. The last thing I want is a big lazy motor. Hope this makes sense, and do any of you guys have experience with this head?
Thanks
Thanks
And I do not know about the "true" numbers, they just seem to have bigger (I know not necessarily better) numbers than comparable heads like the c3, d3, sc1....Only want to do this once, so just short of something like a set of pro-kings to keep the inline look I figures I want to have a motor built to make most power possible with the restraints I have...tired of typing, know u r tired of reading, but I do appreciate all of the feedback....looking for a 4 second small block..
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4,812 Posts
Hypathetically,if you were to have lets say the "wrong" head for your app,could you "offset" this somewhat with valve size,cam,timing?
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4,812 Posts
Double post,sorry.
Losito does awesome work with his billet heads. IMO, id look into doing something with a steeper valve angle and possibly a inline wedge head. Be easier on the valvetrain and pretty sure on your pocketbook as well among a few other things to. Those billet heads go for around 10k or so I believe.
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4,798 Posts
spracr,
Yea the UP heads rock, .. and if you get the proper one's you'll have a rocket on your hands.
I do have experience with those.
If you can't find a set of those, the Edelbrock SC-1 can be a nice
head when properly ported, .. and as Cesar said the Victor / Glidden 2's are a killer in line head.
If it where me, .. I'd go either the UP head like you are asking about
or the Eddy SC-1.
Curtis
Yea the UP heads rock, .. and if you get the proper one's you'll have a rocket on your hands.
I do have experience with those.
If you can't find a set of those, the Edelbrock SC-1 can be a nice
head when properly ported, .. and as Cesar said the Victor / Glidden 2's are a killer in line head.
If it where me, .. I'd go either the UP head like you are asking about
or the Eddy SC-1.
Curtis
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4,812 Posts
The SC1 was the forerunner to the D3 was it not?
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715 Posts
In my opinion, you can't have too much airflow on a nitrous engine, I like to look at the .500" flow number though. When we developed our Neal 295 heads I thought they were HUGE, then came the 311 and eventully the 318's that Lynch, Vincent and tons of others have run. The 318's would go 440cfm peak on our bench (360 @ .500"), the UPM 9 degree billet heads go 460cfm on our bench(375 @ .500") and our new Edelbrock SC1's go 480cfm peak (375 @ .500). The feedback we got on the SC1 heads was 140+mph in the 1/8 on an "easy" single stage shot. I'm not a fan of the Edelbrock SC1's at this point, the CNC program hit water in places in the intake ports where there shouldn't be water. We offer the UPM 9 degree billet heads, that's the direction I would go if I were you.
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