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How to choose the correct cyl head

6K views 16 replies 9 participants last post by  ajensen383 
#1 ·
The title pretty much sums it up, but when choosing a cylinder head, how do you make a knowledgeable decision on what will work the best?? Lets take for instance the major players here, AFR, Brodix, Dart , AllPro and Pro-Filer. Just for the sake of comparison, lets use a 210CC head. All of these companies make a 210 cc head with the exception of All Pro, they have a 220. Now for the general motor head, like myself who does not build engines for a living, just as a hobby, what do we base our decision on? Most people know that flow numbers are important, but not the most important part of what the head is capable of. Besides flow numbers, how would I make an educated decision on what to purchase..I know CSA and throat are extremely important as well, but how would I know what these values are if no one publishes them. I know alot of people will say the new AFR heads are the best, but what makes them the best??? Why/how are they better than the other heads I listed?? Because of flow numbers?? because of magazine tests?? It seems that magazines only test AFR stuff,I would imagine because they are all based in California.. I cant remember seeing a magazine test that used a Brodix or Dart head.. It seems to me that alot of engine builders use a specific brand, because they have good luck with it, or they buy in and get a good deal on them, so its hard to get an objective opinion.. So any insight would be appreciated... Thanks
 
#2 ·
Well, there's flow numbers. If you're comparing heads that are all the same size runner, then you can just compare the flow numbers to each other, but you also want to look at some of the lower lift flow numbers (i.e. both heads may flow the same at .600 lift, but what about at .200, .300?). Also exhaust flow. It seems like the AFR's win in the overall flow comparison approach. Another thing you may have to look at is compatibility for the heads -- Do you need special rocker arms, headers, intake for a particular head (some heads need offset rockers, E-tec heads use a Vortec style intake, etc)? Also, what kind of hardware (valve springs especially) do the heads come with? What options are available? Do the springs match the kind of cam you want to go with?

On my recent 400 build, I picked the AFR 195 Eliminator heads. They cost a little more than some of the competitors, but I could afford the extra and was pretty happy with them. But, all of the other companies you listed are in business for good reasons too...
 
#3 ·
Which head is best will depend on the rest of the build. Cam specs, cubes, use, etc. Things like weight of the car, gears, tranny, stall, etc., may also play a part in chossing the best head. It's the sum of the parts, not A part, that makes the most power or the fastest car. Give us some info on what you've got and what your goal is and you'll get some good advice.
 
#4 ·
Your dilemma is mine as well... What does make a head the best Choice?

For a drag race head, no one cares about saving fuel, but circle track races can hinge on fuel mielage and staying out of the pits.
In my world mileage and the ability to survive on cheaper gas trump the last couple horses for a driver, thus swirl and combustion efficiency could be just as important as flow for a street head.

How can a person determine if AFR, Edelbrock, ot Trick Flow has the most efficient street legal aluminum head? (Are there any other CA legal choices)? Wish I knew the answer to both those questions.

A. G.
 
#5 ·
You call somebody like Mike Lewis who has a lot of dyno experience with lots of engines (big and small) and different combinations of heads. My 555 had 3 different brands of heads tested a lot of knowledge was obtained. Intended use is very important. Give him a call.
 
#6 ·
You call somebody like Mike Lewis who has a lot of dyno experience with lots of engines (big and small) and different combinations of heads. My 555 had 3 different brands of heads tested a lot of knowledge was obtained. Intended use is very important. Give him a call.
:yes: X2 Phone: 707-984-6103
 
#9 ·
#7 ·
Ignore cc sizes, measure the csa, pushrod pinch.
Look at intake valve size (throat)…
whats gonna make more power on a 4.155” bore, a 2.02 or 2.125” valve? A 2.0” p-rod pinch or 2.4”
Why run a 195cc head with only a 2.02” int valve on 400+ cubes, wouldn’t a head with
around 2.4” csa and a 2.125” valve make more power?
Its like running a 2brl carb instead of a 4brl.
Also look at chamber design, RHS 235 has a nice tight chamber.
Make sure the head doesn’t nose over at higher lifts.
Size the csa per CID and rpm.
If youre not sure talk to a porter, and have him do a set of heads for “your combo”
they will make more power then some cookie cutter cnc heads.
 
#8 ·
I understand what you are saying, but how do I find out what the CSA is? or the P-rod pinch area is?? How do I know this? I have done my omework on lift and understand about the whole curve. I just dont know what to look for as far as pinch area and CSA??? I have it down to 2 heads, the Pro-filer 210, or 220 Airwolf(probably too big for a 383 turning 7,000-7200 rpm though) from Chad, or Brodix Track 1 STS 215 CNC... The Brodix seems to be better through out the whole flow curve compared to the Pro-Filer 210, but thats where my knowledge ends, and I'm sure not the whole story. How do I know what the CSA and Pinch is for the Brodix, since they dont list it in their catalog. Granted the 210 will have a smaller CSA, but it also flows less.....This is the part where I get confused.
 
#10 ·
you have to measure it, HxW minus the radius corners.
Call the manufactures and ask.

or better yet get with a good head porter who is familiar with the casting,
he will tell you what you want and help you pick the right head for your app.

So whats the engine?

Also another thing is air speed.
A 220 head can have a smaller P-rod pinch then a 210, happens all the time,
so the air speed can be higher at the pinch with the bigger head.
 
#11 ·
Jeff,
Here is my take on it ...... The people that know the cylinder heads the best are the manufacturers. I would say pick a manufacturer that you feel comfortable with, then call them and ask them which one of thier heads you should use. They want you to be happy so they will recommend the right one.

By the way, I know some will disagree, but .... you get what you pay for :)
 
#12 ·
A 210cc Pro-Filer has a 2.28 in² pinch, moves around 295cfm w/2.08.

A 215cc Brodix STS has a 2.35 in² pinch, moves around 300 cfm w/2.08 .

A 220cc AIR Wolf has a 2.54 in² pinch, moves around 325 cfm w/2.08 and 330+ w/2.100.

The velocity through the pinch is all realitive to how much air it's moving. The final answer is a pitot tube. Localized velocities are a far better way of evaluating a cylinder head. Also, the BEST cylinder head is the one that has the highest coefficent discharge.
 
#13 ·
Chad, thanks for posting the info..Now if I am understanding this correctly, you want the smallest pinch with the largest flow to create more velocity??

How much affect is there in the .07 square inch difference between the 210 pro-filer and 215 Brodix ?? I saw on 1320 tech talk that you flowed a Brodix 215 at around 307cfm out of the box and your 210s flow about 298..The Brodix flows 9 cfm more with .07" more pinch..Are these two cylinder heads about equal with the slight differences in flow and pinch?? I apologize if my questions may sound ordinary, but I am just starting to learn about this stuff in depth.

...Now how does chamber shape work into the equation??? I know the Pro-filers have more of a heart shape chamber as the Brodix is not as heart shaped, how does that affect overall performance??
 
#15 ·
No, not at all. You want a balanced port. You want a good velocity profile. A flow curve shows you only part of what is important. The 210cc is almost perfect IMO. The size vs the profile vs the flow. A good head porter is a velocity manager, not a cfm finder. You get the profile correct, the cfm will follow.

If the port is turbulent at the mid point, backs up, stops flowing or goes into air speed choke the engine will "see" that situation far earlier and far more pronounced in the running engine because the air speeds are much higher. You may see the port stop flowing at .700 lift on the flow bench but in the running engine where peak air speeds can be as high as 150" the choke hits much sooner and cylinder fill is decreased substantially. Its called the MEAN INLET MACH NUMBER. When the MIMN reaches .55 the engine VE stops increasing or decreases at a faster rate. You spike the velocity with turbulence or an air speed choke and the engine stops increase air flow relative to engine speed. People always talk about air speed chokes but a turbulence choke will do the same thing just not as bad. If your turbulent and try to flow more air through turbulent area guess what happens to the air flow, it gets even more turbulent! The more air the engine demands, the more turbulent the flow becomes and the worst the choking situation gets. When a head is growing in flow, it assures us the port shape is correct, therefore the cylinder fill is sufficient. When it's sufficient, at any lift, it will make more power.


The more you turn the engine the more CSA you need. You enlarge the CSA to keep the same air speed.. Every head porter has a targeted velocity they strive for. Put a smaller engine on the same size heads and you must twist it higher in order to achieve the same air flow through the heads in order to get them back in the range where they are efficient ( air speed range). If the head is flowing well, your CSA would be larger. If it's flowing poorly, your CSA would be smaller. Everything is based off of valve size and how much it is flowing.
Chad,thanks for explanation.... Would it be a problem if I called you to discuss my combination??? What is your number and what is the best time to call??..
 
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