Port CCs
#2267238
03/11/17 06:10 AM
03/11/17 06:10 AM
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Joined: Mar 2017
Posts: 43 California USA
LowDeck451
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California USA
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Hey all, new to this site, like it a lot! Been wondering, when talking about port size in CCs, I assume they are measured with a valve installed, if so, the shape of the valve would change the volume, as in, a nail head style compared to a tulip style, stem size etc. I realize it wouldn't be a big difference but, just figured there would be a way of measuring volume without a variable like this. Thanks!
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Re: Port CCs
[Re: LowDeck451]
#2267505
03/11/17 04:59 PM
03/11/17 04:59 PM
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Joined: Jan 2003
Posts: 14,515 So. Burlington, Vt.
fast68plymouth
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The main thing to keep in mind when trying to compare runner volumes is to make sure you're comparing heads of similar port configuration. Raised ports with long valves and extended runners will have more volume than low port heads with std length valves........ Although they wouldn't necessarily have a larger min csa to go along with the extra volume.
The best bet is to compare runner volumes of the same type head to each other. That will give you a better idea how much extra csa the larger port might have.
As an example, an ootb stealth head is 210cc, while the CNC ported version is just over 250cc.
A std port Victor is 280cc, while an EZ-1 is 275cc...... Yet the MW sized EZ-1 actually has the "bigger" intake port.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Port CCs
[Re: LowDeck451]
#2267991
03/12/17 01:36 PM
03/12/17 01:36 PM
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Joined: Nov 2015
Posts: 885 Missouri
jwb123
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super stock
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Missouri
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I use computer engine programs to determine what runner length and port volumes are the best for what ever combination I am trying to put together, the calculations the programs make are way over my math ability, but they give the average guy the ability to make decisions formerly only engineers could calculate and make. After I have a cylinder head for the combination and I flow it on the bench, in porting I try to make the head flow the most cfm with the smallest increase in runner volume, that tells me if I am just making it bigger or I am making the runner more efficient. When looking at getting a CNC ported head, I have to ask the question, whose work did they duplicate, or did they just tell the program to make the ports 15% bigger and keep the same contours? The guys that ask me to help them build engines, most of the time bring me a pile of accumulated parts, wanting me to build a GOOD engine. As far as bolting it together I can make sure all the clearances are sound,and it assembled correctly, but they have to realize they determined what the HP output was when they were walking the swap meet getting all those good deals. When somebody asks me to help and we use a computer program to select the components to meet the HP goals they have set the results are much better. Many times a quick CC check of a head runner tells me those super trick good deal heads are at the swap meet because they have huge ports that are lazy and they made no power.
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Re: Port CCs
[Re: LowDeck451]
#2268051
03/12/17 03:21 PM
03/12/17 03:21 PM
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Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
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Aurora, Colorado
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As mentioned, the port cc's are mainly useful when comparing two of the same type of heads. Different models of heads may have different runner lengths. The McFarland formula relates minimum port cross-section area to the engines peak torque RPM where the port velocity reaches a sonic choke point. The original formula uses velocity of .5 Mach, but others have reported that that is a bit low, and use a higher velocity. Speed Talk has a good thread on it here: http://speedtalk.com/forum/viewtopic.php?t=771Also, there is differences in port shape and taper angle. On some heads, you can fill the ports in places like the floor reducing the port volume, without hurting the total flow of the head, and get better velocity.
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Re: Port CCs
[Re: 451Mopar]
#2268821
03/13/17 07:46 PM
03/13/17 07:46 PM
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Joined: Jan 2003
Posts: 31,105 Oregon
AndyF
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Oregon
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When I watched that Engine masters, I was thinking they should do a show about port cross section area. Dyno the same engine with the same type of head, but different port cross section size and see how the torque curve changes? I'm getting ready to do a back to back dyno test with a 470 inch Mopar. I'll run the Trick Flow 240cc heads on the engine and then replace them with the 270 cc heads. I do expect the torque peak to move up with the larger heads. I'm almost positive that the 470 inches pulls harder on the 240 cc heads than they can deliver. The question will be how does the engine respond to the back to back testing since I'll use the same headers, cam and carb. I should have the answer by the end of the month.
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Re: Port CCs
[Re: 451Mopar]
#2268872
03/13/17 09:09 PM
03/13/17 09:09 PM
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Joined: Mar 2017
Posts: 43 California USA
LowDeck451
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When I watched that Engine masters, I was thinking they should do a show about port cross section area. Dyno the same engine with the same type of head, but different port cross section size and see how the torque curve changes? Me too. I think something like that is coming. In one of their short video 'extras', Dulcich said he would give DF a set of his max ported-relocated pushrod hole Eddy heads. Should be interesting.
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Re: Port CCs
[Re: LowDeck451]
#2269273
03/14/17 12:45 PM
03/14/17 12:45 PM
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Joined: Jan 2003
Posts: 14,515 So. Burlington, Vt.
fast68plymouth
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Speaking in extremely general terms, this is a trend I have seen play out many many times.....
-motors built with nice flowing heads that would generally be thought of as "too small" for the application are often "over achievers".
-cars powered by motors with "bigger" heads seem to often be underachievers, and/or seem to be much fussier about things like cam selection, converter stall speed, rear gear....... Basically the whole combo is less forgiving.
Certainly there are many examples of the bigger heads doing just what they should, or even beating expectations....... But I've seen enough "big head" combos that were duds(of all brands) to know that just having big heads with big flow numbers does not guarantee big power or fast ET's. At the same time, small heads with modest flow numbers often run way better than "conventional wisdom"(or many of the formulas) would suggest.
It's pretty easy to beat the 2hp/cfm(for an 8 cyl engine) yardstick when the heads are on the small side for the build, especially if the rest of the combo is well thought out.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Port CCs
[Re: LowDeck451]
#2269289
03/14/17 12:59 PM
03/14/17 12:59 PM
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Joined: Jan 2003
Posts: 14,515 So. Burlington, Vt.
fast68plymouth
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I'm getting ready to do a back to back dyno test with a 470 inch Mopar. I'll run the Trick Flow 240cc heads on the engine and then replace them with the 270 cc heads. Andy, since it sounds like TF did their testing of the 270 heads using their std port manifold, do you have any plans on trying that yourself? I think it would be a good test, since you've already run it on the 240 heads, so that would be a back-to-back test where the only change was the heads.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Port CCs
[Re: LowDeck451]
#2269944
03/15/17 01:15 PM
03/15/17 01:15 PM
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Joined: Jan 2003
Posts: 14,515 So. Burlington, Vt.
fast68plymouth
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I Live Here
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I'm assuming the peaks you're referring to are horsepower peaks, not tq peaks.
I had a 451 with 300cfm rpm heads making peak hp at 7200rpm, peak tq was in the 5500 range.
I trust the real world results more than I do the computer sims.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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