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Head flow |
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16611 |
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SuperStockAMX
AMC Apprentice Joined: Dec/29/2009 Location: Anthem, Arizona Status: Offline Points: 237 |
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This "luxurywheel" that places Dean Turks ads recently had a pair of "Dean Turk NASCAR AMC NASCAR heads" on ebay. Super rare part, super expensive (I think it was $2500 starting bid) blah, blah, blah. They were standard passenger car heads (291 or 993 as I recall). I sent an email to luxowheel and politely mentioned I had a set of AMC Trapezoid NASCAR heads that look quite a bit different than what he was offering and if Dean wanted to drive north about 30 minutes he could take a look-see. I was told "that's what Dean said, he's the best, etc., etc."
So maybe at one time they were bolted on a NASCAR AMC but I think most would agree there is a difference between the two. My -291's flow 303 CFM and I know Barry Allen and A.H. Adkins can come up at least the same if not better numbers (I assume better) but they're using larger valves than my 2.02" / 1.68" which are required in my class. I also have to maintain 175cc intake runners and 75cc exhaust runners per the class rules. The SS/B through SS/D 390 cross ram SS engine has larger valves and ports volume specs. Since my SS engine (1970 390 w/ Autolite carb) was built, NHRA has been more generous in what is acceptable with valve jobs. We'll be trying new valve angles and the numbers may improve. Probably only slightly, hopefully not worse! My machinist is Bud Yancer of MACH Development. That's Manifold and Cylinder Head Development. And while he has built some competitive Jeep off-road SCORE engines in the past, my heads are the most serious drag race factory AMC heads he has ever done. To suggest one has to be an AMC "guru" on anything related to the engine is nonsense in my opinion. Adkins did provide me with a 5 word clue that was really helpful so I'm glad we can all work together. So I would say based on what has been mentioned here, along with my own results and what I have spoken to with Adkins and Allen, it would appear low 300 CFM range is credible. What I would really like to know is some serious reporting on Trapezoid heads as they are a factory (although over the counter) cast iron cylinder head. I have the last design with the raised / large runner intake and trapezoid exhaust ports. I'd like info on runner volumes, valve sizes, chamber volumes and of course CFM ratings. I'd like to know what the numbers are on relatively stock or "as delivered" (or at least assembled without extensive work) vs. "built to kill". Some other day I will have a use for them. But not today.
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Hurst390
AMC Addicted Joined: Apr/20/2008 Location: secret Status: Offline Points: 5818 |
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trap heads flow about 340 with a 2.08 valve...bigger valves 360cfm.....not bad for 35+ year old iron heads?
Ken Parkman made a port mold off mine a couple years ago in stock form...maybe he will chime in and share the pics compared to other runners he has molded?
Edited by Hurst390 - May/10/2010 at 8:47am |
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SC/Hurst Rambler
11.62 120 100% Street Legal |
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Ken_Parkman
AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1814 |
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Unfortunately we took that mold out too early so it lost some of it's shape. But it's still enough to show the trap head is big time different than a stock iron casting. The csa through the center where you can't make the stock head big enough has been fixed in the trap head - and how! It's way huge where it needs to be to properly feed a bigger valve. The volume is much larger than a stock head.
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beepbeep
AMC Apprentice Joined: Aug/02/2007 Location: WI Status: Offline Points: 86 |
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Mr Ken Parkman, You've done a bunch of flowing on AMC heads. Whats your opinion concerning some of the CFM claims from AMC heads? Over the years we've heard some pretty big numbers but have never seen an actual flow test to back the numbers up. BB
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SuperStockAMX
AMC Apprentice Joined: Dec/29/2009 Location: Anthem, Arizona Status: Offline Points: 237 |
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Ken's opinion will be appreciated but if I may interject, CFM = HP, HP = MPH, numbers don't lie. You can't take one factor out of the equation and get the same results. This is of course relevant to a naturally aspirated engine.
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beepbeep
AMC Apprentice Joined: Aug/02/2007 Location: WI Status: Offline Points: 86 |
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What numbers are you suggesting don'nt lie?
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SuperStockAMX
AMC Apprentice Joined: Dec/29/2009 Location: Anthem, Arizona Status: Offline Points: 237 |
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Using my own examples, my stock eliminator -291 heads (no porting allowed and I had 270 CFM intake flow with 165 cc intake runners against a 175cc spec) made 534 HP which runs in line with the 125 MPH runs I made @ 3160 #'s.
Took another set of -291's for Superstock (porting allowed but stock valve sizes and 175cc runner volume spec) which are 303 CFM and the engine makes 635 HP and runs 132 MPH @ same weight. Ken can chime in with CFM to HP formulas but the bottom line is with no airflow you have no HP. With no HP you have no MPH. You can reverse formulate the probable flow of a set of heads if you know the MPH & distance. Math takes all the BS out of the bench talk.
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SKeown
AMC Addicted Joined: Jul/30/2009 Location: Texas Status: Offline Points: 3085 |
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So, if I run 128 MPH @ 3150 #'s, I've probably wrung out the HP potential of 280 CFM heads? The thing that's confusing, Jim (Hurst390) claims his heads flow 290 something, but look at how fast he runs? Besides he's feeding more inches and isn't taking it easy on it either.
SKeown
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Hurst390
AMC Addicted Joined: Apr/20/2008 Location: secret Status: Offline Points: 5818 |
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superstock do the math for us...2950# 145.11 mph 1320 ft....how many cfm?
Ken post those pics if you get a chance and don't mind...
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SC/Hurst Rambler
11.62 120 100% Street Legal |
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