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Head flow

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beepbeep View Drop Down
AMC Apprentice
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Post Options Post Options   Thanks (0) Thanks(0)   Quote beepbeep Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 10:40am
I asked for Ken Parkmans opinion concerning the large flow numbers being claimed from cast iron production AMC heads. SS came back with a statement "the numbers don't lie". Were you assuming Ken would not agree with the large numbers? Lets just look at it this way. If Jim {hurst390} is respected and assumed to be one of the fasted guys running a cast iron production head and he says his heads are 290 cfm. How is it there are other claims of much bigger flow numbers and Jim is still one of the fastest?? Jims heads are ported we've been told by one of the best, and SS claims his were not ported and flowed 270 only 20 less CFM.?? And SS, if you have a cast set flowing 303 with stock valves, then Jim needs that set and I have a bridge for sale.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SuperStockAMX Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 11:06am
here's all the formula's you should need to make your own calculations. It has CFM requirements, HP to MPH and much more. It's easy to use and will get you in the ballpark. 

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SuperStockAMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SuperStockAMX Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 11:10am
BeepBeep, 
I didn't notice your last post until after I posted the link to the formulas. 
You make a lot of assumptions. There was nothing in my posts to discredit anybody. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 11:21am

First off – I do not believe all the flow numbers floating around. There are certain fundamentals of valve size, angle, chamber shape, and CSA, and some numbers bounced around do not make sense.

 

I’ve also had a few cylinder heads brought by (other makes) with to good to be true flow sheets from somewhere else, and they were to good to be true. Same with dyno numbers.

 

On my bench I have not been able to get some of the big flow numbers that have been bounced around. I have spent a lot of effort to make my machine accurate, creating SEO calibration plates. There is simply not the material in the castings to be removed to get some of these flow numbers. I have gotten higher numbers by getting more radical and porting into water, but that`s not a great plan for most applications.

 

Of course I am willing to be educated – you can always learn. I`d love to see one of these high flowing heads and have it proven that the flow numbers do exist. But I do figure at this point I have a pretty good idea on what it takes; I figure the 2 most powerful NA AMC engines out there (ever?) have my heads.

 

As far as flow equals power that is true – to a point. Obviously the rest of the engine has to be able to convert that flow into power, and blindly making the hole bigger to make more flow (also obviously a bigger hole flows more air) is stupid.

 

There is an old Superflow formula that says there is 2.05 hp per cfm at 28” h2o. That is not correct. You can well exceed that with proper engine design. Hurst390`s engine is probably a perfect example. That thing is clearly extremely efficient everywhere – excellent design. I also have stuff that is way over 2.05 hp per cfm, proven at the track.

 

Another issue is velocity. You get much above mach .55 it all goes for a crap – the engine simply can’t make more power, no mater what the flow number is. Some really high flowing heads simply do not make the power – the CSA and velocity is wrong.

 

The real answer is the track. 1/4 mile MPH and weight takes power – that’s all there is to it.

 

Hurst – that mold really is not good. I’ll take a picture, but everyone has to realize it’s out of shape, and a race intended head like that is really semi-finished, not meant to be used as is. You can’t read a lot into it unless you really understand this stuff.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 4:57pm
BTW the aforementioned 362 cfm would take a 2.15 valve with 100%, efficiency, perfect location in the chamber, and for the engine to make the power you would need an absolute min CSA of about 2.95 sq in. Most of the port would have to be larger than that, especially through the bend. That's over 50% larger than a stock casting. To achieve that you would also need a perfect ssr, not possible with something resembling a stock head. If using a stock casting every wall would need to be cut out and relocated. The end product would be a work of art, and totally sensless to even dream of. If you need a head like that go buy an Indy -1, way cheaper and better.
 
If that's supposed to be from a stock casting, yes, that is one of the numbers I would not believe. Once again, willing to be proven wrong. Anyone got one of those for me to test/analyze?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 5:12pm
the 360 I mentioned is a trapazoid head with a big valve...I was curious about the mold myself compared to an untouched in sr head and a stock iron...no big deal....
SC/Hurst Rambler

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stickshifter View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stickshifter Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 5:55pm
Originally posted by SuperStockAMX SuperStockAMX wrote:

here's all the formula's you should need to make your own calculations. It has CFM requirements, HP to MPH and much more. It's easy to use and will get you in the ballpark. 



Interesting formulas.  Not so sure I believe them.. at all.  I ran a 8.09 at 166 last Sunday at 2650 pounds.  Most of the calculators put this at about 1000 hp.  Now put that into those formulas and it says 486 CFM at 28".  Amazing, because I know my heads are about 20% less than that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SuperStockAMX Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 7:08pm
To say one person is the end all in cylinder head (AMC or otherwise) work, is fooling oneself. That goes for anything in life. Just because some of you can't find 270 CFM on un-ported 2.02" / 1.68" heads (which held the National Record and were completely inspected for legality by accomplished tech members of NHRA), does not make the job impossible. Like you said, Ken, you do have room to learn and I hope you get there someday.  And I imagine my engine builder would put you to shame on cylinder head work on any level; not to mention the rest of the engine. He's 58 years old and has been doing this since he was a teen. Since you don't want to believe me and you really do think 300+ CFM is out of touch with reality on an AMC production head, call up Adkins and Allen and tell them you have a bridge to sell also. Because they have -291 & -993 production heads going low 9's at 143 or so with 3200 # cars. . 
Stickshifter, I see you have made improvements to the car and ar now only .15 away from the formula of 1320 / MPH = optimum ET which you previously stated wouldn't work. I believe the last time we discussed this you were running 8.25's or so. Congratulations, you're getting there. 7.95 is still obtainable @ 166 MPH. Good luck. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote DragRacingSpirit Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 7:27pm
270 cfm out of unported iron casting doesn't sound possible to me.
 
When you say unported I assume that you mean a die grinder has never touched them in any way and the ports are exactly the way they left the factory ?
 
So what you are saying is that you can go to a junkyard, pull off an iron AMC head of whatever casting number, clean them up/recondition them to 100% stock specs, do a fancy valve job and get them to flow a peak number of 270 cfm on the intake port ?
 
I'm sorry but if I see it on my porters flow bench with my own eyes I will believe it.
 
 
Best 1/4 mile 8.99, 1/8 mile 5.71, 60 foot 1.27, no power adders
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: May/11/2010 at 7:37pm
Jeff you really are a piece of work. You'll note I was talking about the 362 cfm you also didn't believe. I was not commenting on you or your builder.
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