Had a very interesting phone call with David Vizard this week (if your not an AFR fan skip to the next thread! ) that I thought was worth sharing...

I wont even bother with details of the other brand in an effort to keep this more technical but it was a popular aftermarket 220 something full CNC piece that's highly regarded and flows over 300 CFM peak.

The engine in question was a 383 CID pump gas piece (10 to 1 or so static CR) that a particular shop I also wont mention was building/designing to offer as a turn key crate engine. It had a 230 something hydraulic roller and an air gap Edelbrock intake. David was hired as a consultant and from the onset of the project felt the cylinder head choice wasn't optimal considering it was a hydraulic roller (limited RPM) and a dual plane intake (also limited RPM). He mentioned based on all the testing he had done that our 195 street head might be a better choice for a more well rounded package, not to mention was considerably cheaper than the head they choose.

Fast forward to dyno time.....David spends a day or two wringing out the combo (worth the effort due to the fact it was a prototype that technically many others would be duplicated from) including stagger jetting the carb for best results. When the smoke from the dyno cell finally clears, he hits the HP target of the project (which he didn't share and isn't really relevant) but he felt the area under the curve was weak and he was still really curious what a 195 AFR street head would do. Pointing to the weaker part of the dyno curve he ultimately talks the engine shop into trying the AFR's...

I get the "fire alarm" phone call with the engine still hot on the dyno and within a few short days jump thru hoops to build him a set of 195's with the same chamber volume as the current heads (so the CR stays the same) and shortly after get the heads in a box and airfreight them across the country so he can do a back to back comparison. Honestly, neither one of us was expecting the same peak number, but both of us were hoping it would be close because looking at the usable flow numbers in this test (.550 lift and less), the AFR 195 street head (not the more expensive Comp version) had similar or better flow with a significantly smaller runner. What we were hoping for was much stronger low RPM numbers and a much fatter curve that would really be more usable to the end user looking for a good all around pump gas 383 (a street/strip combo with the emphasis placed on street).

I finally heard the results from this test about a week ago and I could tell by the excitement in David's voice that it went pretty well. Unfortunately I don't have a graph to post, but the key points I remember from the conversation was that there was a gain of 40 ft/lbs at 2000 RPM (that's insane btw....it would be the equivalent of stepping from a 350 to a 388 or so at that RPM level), a peak gain of 12 ft/lbs (purely comparing peak to peak numbers), and perhaps even more surprising is the fact we made one more HP once again comparing peak to peak numbers. David said the two curves looked like we took the same top-end (heads, cam, induction, etc,) and installed it on an engine some 30 cubic inches larger.

What can we potentially learn here....choosing the right head is paramount for a particular application, and that even a head that flows more peak numbers, if not sized properly for the application (or used in the wrong application) can and will hurt the final output of the combination, especially if the peak numbers arrive higher than any usable point taking into account the camshaft and type of valvtrain in the combo. Even looking at a cam that lifts the valve to .600 lift with a 1.6 rocker for instance, looking at the .600 numbers when comparing heads are almost useless. With a typical stud mount system and a 5/16 pushrod, under operating conditions due to parts deflection you might only see a true net of .570 peak valve lift and only see that for a nano second....a couple of crank degrees across the top of the cam lobe. BUT....looking at the .550 number and more importantly the .500 number in this hypothetical exercise would be far more beneficial (especially weighing that number against cross sectional area if comparing two heads) because that same combo might be over .500 lift for 80-100 crank degrees approaching full lift and heading back from it across the broader nose of the cam. I always advise our customers to look at what head will work well considering .050 less than peak lift and below (always look for strong low and mid-lift numbers as well) with a hydraulic cam and .075-.100 less with a mechanical to account for the added .020 valve lash. Meaning with a .675 solid roller, .600 and below would be the area of most interest concerning cylinder head flow...once again always weighted against port volume to keep good airspeed in the picture).

BTW, a 195 Comp would have really rocked on this combo (more flow....same volume and cross section), but one of the angles David shared with the shop was that if his hunch was right about the 195 AFR street heads, not only would they have a better power curve, but a package they could charge $500 less and put more money in there pocket....kind of a no brainer if you will.

Sorry I don't have exact numbers....I will likely be speaking with Dave in the near future on a couple of other projects he is working on....if I can squeeze him for more specifics I will....I tried to get the comparison dyno graphs for my own knowledge, but he didn't have that handy and at the time I didn't want to push him for them....I could tell he was doing a little "political back peddling" if you will so at the time I respected the info he shared and hung up. IMO the actual numbers don't really matter....the information and delta between the two is the meat and potato's of the info we crave.

Oh yeah....picture the PART THROTTLE difference between the two combo's....how about night and day with a 30cc smaller intake runner. In fact David mentioned as soon as the engine fired to life with the AFR's on it, he could tell the engine had alot more "snap" as he put it and ended up requiring less jet to make its best numbers.

Good stuff...

Have a good weekend everyone

Regards,
Tony

 

I am not suprised to say the least. It sounds like the 195's will work on many different cubic inch engines.

Take it easy!

 

Thats a lot of torque..... a street motor with a tight converter would do more than just feel that, it would show up substantially on the et slip as well. I would not have expected the match in HP too.

I'd like to see more information on the dyno test.

Thanks for sharing !

 

40 lb-ft is nuts ! thanks for sharing ! This sounds like a good example of a ported head that has awesome peak #s but not so awesome low-mid lift #s.

 

I think it's also useful to see how important having smaller ports on intake runners helps with low-end power production. To be honest, I am suprised at a 40lb improvement. That is really I'm duly impressed!

I read (and understood) early in my process to look at subtract .1" from cam lift to determine flow. Also, compare lifts at .2, .3, and .4. Is it really the case that the cam holds the valve open within .050" of max lift for ~ 90 degrees? If so, that's more peak lift duration than I thought.

Personally, I'm still juggling the choice between a 180 vs 195 on a 350 block, but clearly your 195 worked better than the larger option on a 383.

And, I'm planning on ordering a set of your heads once I figure out the last of the details.



Gregg

 

hmm sounds like he was using the Track 1's fully CNC head...being those are the only other cnc 220 something heads i know of


Does go to show matching the head to the combo is more important than just flow. its not just flow you need to match port size/runner volume and valve size/etc to the engine.

Also to add this isnt the first time i've heard of a case where a smaller cc head that flowed more than a larger cc head made more useable power and sometimes more peak power. Just so happens to be that most of the head swaps i've seen by a few racing buddies have been to AFR's as they generally have the flow per cc advantage over other brands. Those guys all have seen good power gains.

I dont see why alot of ppl argue against AFR. If you need a 195-200 cc head for your application (your engine size, rpm range, hp goals, etc) then get the one that flows most for the port size. Eliminators seem to be the top dog at this time in flow per port size and the price isnt that much more than other heads out there

 

"(if your not an AFR fan skip to the next thread! )" Hehehehehehehe.

Excellent information Tony. I can't wait to get my combination together. We are going to see what a TPI system can do. I'm still seriously considering 3/8" pushrods to cut down on the flex.

 

idk, the most premium pushrods may be fine but with the rpm you intend to turn with a hyd roller cam, maybe your better off with bigger pushrods What are you doing for valve spring pressures? I think the AFR 8019 springs with some shimming should handle the load. I got them shimmed to 166-170 lbs on the exhaust/intake and its working good for my 6500 rpms or so

 

AAAHHHHHH!!! I can't put up with all this marketing!!! I'm starting to feel violated!

On a serious note, thanks for the info, hopefully when the shop is done and testing and tuning is complete they can release some more info and maybe the dyno charts as well. You really do have to stop posting stuff like this though or else I'll be forced to do an AFR comparison on my car sooner than I wanted to!

 

Tony can you post up the flow #s for AFR's 190 or 195 heads. Id like to compare them to my ported 190cc stock heads flow #s done by A.I to see how the lower to middle range compare. Thanks

 

"the most premium pushrods may be fine but with the rpm you intend to turn with a hyd roller cam, maybe your better off with bigger pushrods What are you doing for valve spring pressures? I think the AFR 8019 springs with some shimming should handle the load."

Yes, the Comp heads come with the 8019 springs. I'm also going to use the AFR hydra-rev kit. I'm not going to take any chances since I'm also going with 1.65 roller rockers.

 

From their website, here are the numbers for the AFR 195 Eliminator Competition heads...

 

It would be nice to see the Dyno sheet on this test too; though I doubt it would ever convince some, of anything. Even with David Vizard doing it. I think it would have been real nice to have seen what the Competition version would do. You should talk Joe Sherman into doing some Head comparisons if he's not too busy. Just have him keep the Cam "reasonable" with the RPM under 8000.

 

Here you go!!! What were your flow #'s? http://forums.corvetteforum.com/c4-t...-addition.html

 

I only ask because I know AFR's are a leader in heads and its nice to have a reference to compare to.
My flow#s 190cc/exh 78cc
.200 146/115
.300 202/153
.400 244/172
.500 268/187
.550 274/190
.600 275/193
.700 273/196
Stock LT1 heads ported by A.I
Congrats on your baby Rick

 

To say I am not suprised is an understatement.
Please post up the graphs when they become available. Until then, it is only an interesting story.

 

In one of the other AFR vs other heads threads, i posted up a bunch of info on a small block drag motor setup a guy had. He bought some cnc'd Brodix 227 heads i believe it was because he didnt feel like waiting for the new AFR 227's and didnt want to change pistons for the 60/40 valve spacing. After getting the brodix heads he had them flowed and checked out. they numbers were far less impressive to 600 lift than his old AFR 210's, non eliminators that is. Brodix cnc 227's only then made 15cfm more at .750 lift. Not many guys running cams that high in lift even on most race motors using 23 degree heads.

Sad thing was out of the box he didnt go any faster than the old AFR210 combo. I believe that AFR210 combo was a 388 while this new motor was a 427 brodix 227 head. After he had the heads hogged out, 1200 dollar port job, only then did he really pick up.

 

Sounds good, but I really would like to see a specific example with definite specs.

 

My bet is on the 227CNC Darts. Here's the flow numbers from a CarCraft build up,, which is a good bit short of Dart's published 309cfm/226cfm flow at .700 lift.
Dart 227 CNC
Lift - Intake . Exhaust
.100 - 65 ........ 53
.200 - 145 ...... 110
.300 - 197 ...... 148
.400 - 242 ...... 178
.500 - 272 ...... 196
.600 - 283 ...... 208
.700 - 287 ...... 215

IF it were these Darts,,, and IF CarCraft's flow numbers are typical,,, they (Dart 227s) don't flow any more than the standard 195AFRs,, in fact a little less on the exhaust side.

I've never been that much of a fan of the older AFR heads, but I recently had a pair of the 195 Competition Ported AFR Eliminators in my hands,,, and I've never seen a set of heads look any better. Tony's put in all the tricks (while keeping a standard intake port alignment). What really caught my eye was the valve pocket area,,,, there’s just not enough meat in most heads (at least those I've ported) to get that desirable of a shape. Another area was the runner floor which is reminiscent of an epoxied 18-degree floor. I'm no suck up, but I gotta give credit where it is due and these AFR Eliminators have definitely set the bar as far as mass consumption out-of-the-box heads go.

 

yeah that sounds about right, i forgot about the dart cnc heads.