cv67

At wot on a dyno, on the street its a different deal altogether.

REELAV8R

suprspooky

Aren't the 041 heads Cast Iron? I was under the impression that Cast Iron vs. Alum. (similar flowing heads with similar combustion chamber/comp. ratio), the Cast Iron is putting more power to the crank? I understand that the AFR's have better flow/combustion shape (and probably better port vel.), I am curious as to whether the heat/HP loss from the Alum. will offset the gain if not changing the Cam to better utilize the flow ability of the AFR's? I pose this because I'm thinking about some AFR's for a new project that has Cast Iron Heads (around 300hp and not changing cam or anything else).

gkull

2.1 min CSA is probably why my 383 works so well with AFR 210 heads. Heads can be a lifetime purchase, so go big for later expansion.

76strokervette

The formula Adam posted is the best way to determine head size.

REELAV8R

Jebbysan

I also want to add here that milling the divider negates the advantage of carb signal on an Air Gap intake......it just becomes a crummy flowing single plane after that. But this works for cheater classes or classes that require a dual plane intake.
I myself plan on securing a Winters LT-1/DZ302 intake for my own 406 and milling the divider out completely.
On EFI......having the airspeed equal on all ports as the air goes by the injector makes for a happy setup.......a single plane intake achieves that for the most part.
Someday I would like to EFI a big small block and use a Weiand Tunnel ram as the intake.......I think a tunnel ram EFI would be VERY happy.

I also want to add that I wished that Dart did not even make the SHP head.......to me, the SHP is a false bargain because it does away with the 5 angle valve job that the platinum's have......and that is everything.


Jebby

REELAV8R

The SHP has the 5 angle grind on the intake. You talking about on the exhaust?

Jebbysan

gkull

All the motors that I cared about for the past 25 years got Manley raceflow or severe duty valves. Because of the radiused design they are superior to the total flow of multi back cut angles. this was all proved on flow benches. Put your money where it counts and not into so time intensive multi cut setup. My Dart 227's use 2.100 and 1.625 manley valves

http://manleyperformance.com/dl/cat/valves.pdf

https://www.summitracing.com/nv/search?SortBy=BestKeywordMatch&SortOrder =Ascending&keyword=Manley%20Race%20Serie s%20Stainless%20Steel%20Valves

REELAV8R

Despite the 5 angle grind into the intakes the blending was very poor on my heads. The valve seats themselves were not evenly pressed into the head. I did quite a bit of blending work on both the intake and the exhaust on those heads. The dart's were lightyears abhead of the 882's I pulled off but I feel they fail ultimately to compete in the aftermarket aluminum heads of today.
I didn't have to even touch the AFR heads. Although I did polish the exhaust ports rather than leaving the CNC cuts in them. Intake, didn't have to do anything. Dart SHP's are cheaper, and the reason for that becomes apparent.

Jebbysan

Anything we ever built always improved with a 5 angle job........not so much high lift numbers but .200-.300 numbers.......I paid attention to this and the car in my Avatar had a pair of 461's with a five angle job and blend with Ferrera 5000 valves......they were comparable to the Edelbrock RPM head in flow but the mid lift numbers kicked it's ***. That 331 ran VERY well with a spec L-79 cam and 1.6 rockers........
I agree on Manley valves.....but for the sake of conversation I was pointing out the 5 angle or lack of it as the reduction in price point for the SHP.......they just dont work as well and are not that much cheaper.
My 200 Platinums on my 406 have a super high quality valve job and very good blending work too....(They must have been done on Friday LOL). I was impressed with these heads and they work extremely well.....
Mid lift number get the charge moving and help with VE......VE is power.....If one pays too much attention to peak flow numbers then the build can suffer.

Jebby

NewbVetteGuy

Yep.

The airflow velocity formula highlights why very well.
FPS = (CFM * 2.4 ) / CSA


-I did this on here once before but if you take the min CSA for the AFR 180, 190 and 210 heads and then the airflow charts for each of these heads at each .100" of valve lift, you can plug the values into the airflow formula and the strange thing is that because the AFR 210 head flows more for the amount of area it has, that the port speed is better than the AFR 195 head. The 210 head is the most efficient of the lineup. (Flow vs. CSA.) -I think the FPS calculation ASSUMES that your piston demand on the intake stroke at each of those lifts and given your cam timing is actually demanding the full airflow that the head flows at that lift, though. (If the head flows more than the piston is demanding then you're actually getting less airflow through the port and therefore less port speed, right?)

(So again, I think that calculation is really just for the flowbench and assumes you haven't over sized the head...)

Regardless, I haven't seen a head that flows more CFM for the min CSA vs. the AFR 210 -so my guess is that if you're going to go one step too big with a set of 23 degree heads, the AFR 210 will see the least downside / reduction in low end torque.


Adam

NewbVetteGuy

Here's the Chad Speier article on the head sizing formula: http://speierracingheads.com/head-size-info.html
-This is also why Chad's numbering system for his heads are always based off of MinCSA and he clearly lists the intended application in cubic inches and max RPM before the port goes turbulent / chokes.

Adam

larrywalk

To answer your original question, my rule of thumb for peak horsepower is to double the flow of the heads to estimate peak horsepower - , ASSUMING THAT THE REST OF THE ENGINE IS OPTIMIZED WITH AN INDUCTION SYSTEM, CAMSHAFT AND SUFFICIENT RPM TO ACTUALLY ACHIEVE THAT AIRFLOW. Therefore, I would say that the 180s could support a peak of 520 hp and the 195s could peak at 548 hp.

68post

You may be at a crossroad that isn't easily decided. It's good that you are comparing, what we'll guess is a properly ported iron head (they seem to be), to an AL head that is a step above most ,if not all others, in as cast form. Others may not really offer a big enough improvement !
My opinion is that to take advantage and be cost effective to swap you'll want to raise compression too - unless you're already fighting detonation.
Also your cam, if optimized to your current combo, may warrant changing to take advantage , and/or your rocker arms. At the very least to gain lift on the intake side, the ex side of an AFR is VERY efficient.

Do everything right and you will notice the upgrade !

NewbVetteGuy

What cam did you have on this before? How did you come up with the HP and TQ #'s for the current engine? (Unless you've got a WAY bigger cam on it now, the peak #'s seem pretty inflated...)

I just modeled a 383 with AFR 195cc heads, 10:1 static CR, 850 CFM carb, dual plane high flow intake, 1 5/8" headers- full exhaust w mufflers and a Howards cam I could actually find. -I can't find ANY howard cam with the specs that you listed (512" lift).

I used Howards 11145-10; 1,500-5600 hydraulic roller 272/278, 219j/225, 110 LSA, ICL 106, .525" lift on both intake and exhaust (AFR Heads will like the extra lift).


I get 454 HP @ 6,000 RPM and 446 ft lbs @ 4500 RPM. With the AFR 195 combo.

If you step up to a slightly more aggressive cam lobe with similar seat-to-seat durations and 1.6 RRs. (Mike Jones HR70375, 272/280, 230/232, 110 LSA, 107 ICL, .600" / 0.575" lift (with 1.6 RRs), I get 466 HP @ 6,000 and 465 ft lbs @ 4,500.



Adam

jb78L-82

FWIW-There a couple of guys on the forum with 355's, 10.5 compression, Howards .560/.560 lift roller cam and AFR 195's making a comfortable 475-480 gross HP......360 RWHP!

The Howards cam above that Adam referenced I have in my 10.2 compression 355 with AFR 180's. I certainly would be looking at a higher duration Howards roller with lift of at least .550+ and you will be banging on 500+ Gross Hp with a 383 and AFR 195's. I have said this before and will again. The old adage of making big HP can only be done with cubes is still true but it can now be accomplished with smaller motors more easily, if desired. A 355 can make 425-450 Gross HP pretty easily with the right combination of parts. If you are going for a 383, make the most of the cubes and you should be shooting for 450+ Gross HP.

REELAV8R

The 1 5/8" primaries are gonna choke the power output in the high RPM range.
Square up the durations, use 1 7/8" primaries and put the cam on a 108 LSA with a 106 centerline. then run it.
In fact on a 383 I'd run 107 or even 106 LSA with his current duration.

REELAV8R

Yes. would be the reason for low RPM poor performance. So a 210 is not going to run well on a small motor at low RPM.

What I found was that the dual plane intake is really the restriction. The heads be they 180 or 195 can flow great, but only if the intake can also. So the min CSA needs to be applied to the intake manifold as well. A performer 2101 has small ports, MSA that varies around 1.5 to 1.6. Since the AFR 180 has a Min CSA of 1.81 then the 2101 is not likely going to be able to feed the head. Either a different intake is needed or the current 2101 needs to be ported out. I ported mine out.
So If the 195 heads are used then in order to take advantage of the additional flow an adequate intake manifold must be used as well.