Well the consensus is.....the bigger the head you got, the better off you are. . . . .ahhh, well ahhh....wrong forum...

 

that 280 will support near 6500 rpm peak power on a 383, probly peak by 6300 but only if you can control it. 8019 springs are nice

For that crossram like intake, i'm not sure what the port size is..probly 1205. Alot of 200cc heads are 1206. I'm not sure, i think the IK's are 1206 and possibly the race rites. Darts pro 1 may still be 1205. AFR 195 is 1205. Be careful on that, if you cant port the intake dont get the bigger head.

Either way i still run a 190-200 cc head on a 383 reguardless of your build goals

 

The AFR "Comp" ports are 1206. The standard ports are 1205.

 

NO, I didn't hand port my heads. It was not necessary for me based on what I wanted. I had Dart clean up the the bowls on the CNC before it left the factory, at which time the cleaned up the ports a bit to get me where I needed to be. A couple CFM either way, I really could care less. I don't get off on flow numbers or dyno sheets (pieces of paper).....just making one bad *** motor..

The point I was making is that it seems that people who build real performance motors for a living seem to have quite a different opinion than people who screw together parts for a street motor. And the results of those people desire in real race motors are far more demanding than these street toys we play with.. Motors costing 10s of thousands of dollars have certain things that builders do to make them right, they can't all be wrong.

Anyway, seems this thread is going down the leg humping route once again, shame really, but not surprised.

 

Exactly. Look what happened after your post. Leg humper central...no one will be happy until qws changes his mind and does the "right thing"....I am sure he has been inundated with PMs telling him he's not doing it right and he can get more power...blah blah blah.....

sick isn't it?

Just another AFR is wonderful thread.....I am sure we will all benefit from the insight.

 

I'm going to address a couple of things a quick before I get to the OP's questions. First, the comment Jesup made about us preferring to hand port over CNC is a valid one. If I were in the business of coming up with "one size fits all" engine solutions I would get into CNC'ing heads. The point is this (and was already posted for me); when we design an engine combination for a racer we look at a wide range of parameters that they lay out for us. These are things like, what's the weight of the car, how's the car set up, how do they drive the car during the race, what do they want the engine to do so on and so forth.

Once we analyze this list we end up with a very application specific solution, one so specific, that a run of the mil head does not fit the bill. Having a head that flows the most possible is not always an option (believe it or not) nor is getting the required amount of flow through the smallest possible runner. I'll give you an example of what I'm talking about; there's a road racing class out there that runs standard production blocks, valve angles....on and on. They also run a fair amount of laps and can only have a set amount of fuel on board. Now when we do the math on fuel consumption we find that a 355 can only turn 7500 RPM and make around 500hp to finish the race on the required amount of gas (there are no pit stops allowed, pull it in and you're done). I think everyone here would agree that a head that flows in the 275ish range will get us to 500 bhp at those revs. Now here's the tricky part, what head do you think we should run if the the car is 2250 lbs, geared closely (5 speed straight cut gearbox), and operates only in the 4000-8000 RPM range?

Now this question is one that we are faced with everyday; not just "how do I get more power" but here's exactly what I need, give me the "best" combination. Now, you will find that a very specifically designed head/intake runner fits the bill and all others leave much to be desired in there own specific areas. There is sooo much more to how a cylinder head makes power than simply sucking air through it that at high levels, a CFM rating and a CC sizing is not enough.

Now to answer the question; what head would be the best for this application? We have to stick to 23* valve angle and that's it. So here's what we developed for that engine; the bare casting started life as a Brodix -10X (this head utilizes a 0.450 offset shaft rocker system coupled with a 0.180 offset intake rocker to eliminate the pushrod hump and accommodate the 40/60 valve spacing and is a raised port design). Now after a little bit of engineering work we decided on a port design. The end result is a port that was a meager 174cc's, flowed a little above 275cfm @ 28", and had a mcsa large enough to be properly tuned for a 355 operating at 7500 RPM.

Now there's no question that CNC'ing is the best way to mass produce and sell heads (and for racing teams that have to produce a large volume of heads/engines for each season, all for one class/car/driver) but to come to the conclusion that everyone should quit porting heads by hand is a little extreme and I feel has been proven at many racing levels to be the only way to get the best combinations for every engine. What gain would there have been in having the expense of 1) owning the CNC machine and 2) setting it up to finish the one set of heads only? If you get really big into air/fuel distribution you will find that even on a CNC’d head you will not achieve the exact same mixture to each cylinder (when working on a carbureted application which many racing classes are rules limited to)

Now this whole notion that for any application the head that delivers the required airflow while having the smallest intake runner will make the most power is a big misconception. Many, well, most of you are under the impression that having a cylinder head that flows more CFM with a smaller runner is "more efficient" and has a lot of "cylinder packing velocity" right (I can't imagine where you got that idea and frankly, without having a background in differential equations and experience with computational fluid dynamics how you would you know any better?)? Well here's the problem, when you look at tuning an intake port you have to look at the velocity of the pulses (imagine that, the engine doesn’t continually suck air through the head). Now there comes a point where too much velocity is severely detrimental to the process (not to mention it will make you do things to the intake tract that are counter productive in the first place) and will in fact lead to a scenario where an engine performs much better in its intended operating range with a larger head that flows a little less than a considerably smaller one.

I think that about sums up most of the problems that are going on here (without typing things that no one would understand); we have people talking with manufacturers, racers, and fellow forum members. There's a reason that they all (excluding the manufacturers) come to engine builders to work on their engines (at least all the fast racers in my area do...). This isn't bolting together parts like everyone wants to make it out to be; this is a highly competitive very technical field that has moved more along the lines of engineering as apposed to mechanics.

Sorry for the long ready, now to the OP's question. You need to nail down your intended operating range (and I mean hard and fast, not to change unless you want to redesign the combination) and go from there. Once you have that number you can start to look at what mcsa will produce the proper amount of airspeed at the RPM limit and find a head with that size or slightly larger. With a standard valve spacing and non offset valve train gear an average 210 cc intake port will do the job (this is assuming that you want the engine to pull to 6500 RPM without letting up; a big difference from just limping up there like most do). Once the mcsa is determined, the flow will help determine the VE and therefore the hp potential and the break specific fuel consumption. Again sorry for the long read, hope this helps everyone look a little deeper into how the many aspects of cylinder head design come together to produce the final result.

 

Hey Deakins, GREAT POST but you're pissing in the wind.....no one wants to hear it, it's all about the circle jerk.

I for one thank you for taking the time to post your thoughts, probably the most qualified guy in this thread to make assertions. But it really, won't matter. The leg humping has started and we're just waiting for the finale.

Bears repeating:

Quote:

Now this whole notion that for any application the head that delivers the required airflow while having the smallest intake runner will make the most power is a big misconception. Many, well, most of you are under the impression that having a cylinder head that flows more CFM with a smaller runner is "more efficient" and has a lot of "cylinder packing velocity" right (I can't imagine where you got that idea and frankly, without having a background in differential equations and experience with computational fluid dynamics how you would you know any better?)? Well here's the problem, when you look at tuning an intake port you have to look at the velocity of the pulses (imagine that, the engine doesn’t continually suck air through the head). Now there comes a point where too much velocity is severely detrimental to the process (not to mention it will make you do things to the intake tract that are counter productive in the first place) and will in fact lead to a scenario where an engine performs much better in its intended operating range with a larger head that flows a little less than a considerably smaller one.

But wtf does he know anyway, he didn't work in a dyno shop........he simply is an engineer that understands the math and builds high end motors for a living....bah....

I am waiting with bated breath for the "race motors have nothing to do with it" crowd........I guess the laws of physics don't apply in the street motor universe.

 

Great points. Pick a head with less velocity, less efficiency no reason to go buy good stuff. In fact, might as well stick with crappy old old cast iron heads, none of this new stuff makes any $ense its all a marketing scam.

 

So I guess you don't want to hear Deakin's insight as an engineer, and engine builder......

Thanks for making my point... He's pissing in the wind no one wants to hear it..

Let's not all try to think too deeply about this, just keep it on the surface where it fits our pre conceived ideas and fits in with the crowd.

Is it your position that Deakin's input on the matter has no value? That he is talking out of his ***? That only someone who makes a product can be the arbiter of good information? Or that it's simply too much to think about for the forum simpletons?

Just wondering...

Because as far as I can see, the guys that I spoke to with the biggest, strongest resume's seem to be saying the same thing....and I'd throw Deakins in that crowd. And what they say, is in conflict with folk lure....

 

yes the point of too much velocity is true, there is a point on a head that will choke the cylinder port. i believe its in the 330-350 fps range. You have to look at your actual cfm at the rpms your tuning to see how much air the motor needs and is flowing and compare to the cross section of the port and figure out your port velocities. Plus the port shape has influence on the choke velocity and where that point occurs which all effect power

For the most part tho, with most cars being under 6500 rpms i dont think hitting the port velocity limit is too common. COuld be but i'm not sure. Seems to me that this issue of flow velocity is much more important on race motors that turn much higher rpms

 

If youre referring to air stalling I agree, dont see it happening much in most of our applications.

Jsup-you missed the maybe I shoulda used a

 

Gee I wonder how long all those professional engine builders would be in business if they told their customers "you're not getting a flow sheet on the heads I sold you and you're not getting a dyno sheet either. I built you a bad *** motor and it is, because I say it is you leg humper"

 

You're ok ron, I don't care what anyone says!!!!

 

OK, let's look at the numbers shall we? Hopefully this will put an end to all the bullcrap once and for all shall we?

http://www.dartshp.com/pdf/SHPTopEndFlyer.pdf

Build:

Dart 400 block 200 CC non machined heads. Results 525 HP

TOP END KITS
Dart 200cc Iron Eagle or PRO1 Aluminum Heads
Assembled With Stainless Steel Valves, Springs, etc.
Dart Dual Plane Intake Manifold
Chrome Valve Covers
Fasteners, Gaskets and Spark Plugs
ENGINE PERFORMANCE
With Hydraulic Roller Cam (230 @ .050)
750 cfm Carburetor
525 HP @ 6000 RPM
525 Ft. Lbs. @ 4000 RPM
CR: 10.7:1 w/ 64cc Chambers & .045” Gasket


AFR Fully Machined Heads:
http://www.airflowresearch.com/chevy_dyno.php
Fuel: 550 HP 406 Street Engine
406ci
AFR CNC Cyl. Heads 210cc Race Ready
10.3
750 Carb
MSD HEI Billet Distributor 36° Timing
Lunati Hyd. Roller Cams 232°/242°
0560-.570 lift W/ 1.6 Rockers
1 3/4" Headers
93 Octane Pump Gas


Difference where we find the 25HP:

6 more cubic inches
2 degrees more cam
10CC bigger heads
FULLY MACHINED HEADS

The difference at the end of the day, 25HP, which probably comes more from the cam. Plus we don't know where that 25 HP is, maybe they are spinning it to 7K.... So it would be my contention that the Dart heads that are NOT fully CNC'd are performing pretty dam well. Can you imagine what a little porting would do? The numbers would be identical on the Darts, with less cam, etc..... if not better. Question is, who's marketing do you believe...

Can we now stop this foolishness about power on the table and all the rest of the bull.

All good name heads are all basically equal. With different setups one may have an advantage over another, but all in all, mostly the same.

 

This is intersting to me and you explain a little better so I can completely understand?
Are you saying that if you lose velocity/charge at some point in the ports the motor can choke itself out per say and lose power?
Or am I getting this all backwards.

 

That's the marketing position anyway. Deakins, a learned engineer who studied fluid dynamics in one of the most complex environments in existence, aeronautics, says differently.

If it were me, I'd take his work over anything anyone posts here.

Did I mention his living is made by building very expensive high performance engines?

Paper plus experience doesn't lie. If you don't understand what he wrote, PM him, he'd be glad to explain it. I can vouch for his frustration trying to do so publicly.

In my opinion any answer you're going to get from this point forward, you can garner from reading marketing brochures.

 

Interesting posts by some. In any regards, at the end of the day, it doesn't matter what cylinder head somebody choses.....you're going to run what you run.... and thats all there is to it. We all make our own bed so to speak.

jsup, with the above analogy, to be fair to the AFR cylinder head in the test above, that is just an off the shelf older version AFR 210 cylinder head that is "not" fully machined and typically sold for approxmiately $ 1295 with springs/retainers/valves,etc....(The race ready's were the lower cost version of AFR's.....) , and also that AFR equipped motor had almost a 1/2 point less compression. And they weren't really spinning the motor, I believe it made its peak by 5500 rpm in that dyno. By reports by guys like Joe Sherman & David Vizard, the new AFR Eliminator cylinder head will make 30-40 HP over the older version...... but who knows.

But, it doesn't matter, both cylinder heads are capable of making good power....... pick your poison and have fun !!

cheers,
Beach Bum

 

Maybe the OP would like his thread back now.

 

I accept the premise. however, the Darts aren't fully ported, so I would assume by your post that fully porting the Darts is also good for 40-50 HP? To be fair....right?

The compression represents single digit HP, maybe.

But, yes, pick your poison

 

It's getting close.

...and any more personal insults and to those who participate.