The first column shows the intk/exst flow numbers in JimV's post #28 are from an 357 AFR CNC ported head out of the box. The second column shows the same AFR heads only with a chamber port done by JimV. The third column shows the Dart heads (don't know the size but probably comparable in size to the 357 AFR's).

The reason I know this is because the AFR heads JimV is speaking of are [/B]MY heads[B]. I took them over to his shop because I looked Jim in the eye and told him I wanted to know the truth about the AFR head flow numbers, and also without any 6 inch "cheater pipe"---nothing more...nothing less, and Jim flowed them for me while I stood over his shoulder. My first reason for doing a chamber port was because I wanted to reduce the comp ratio of my engines to 9.3, so I had JimV do a chamber port to the heads to increase more volume in the combustion chambers. Jim also told me that the added bennifit was that a chamber port would also most likely increase the flow numbers as well without even going into the ports----and he was right! However, as Jim points out the exhaust flow numbers don't increase much after .500" lift.

I only plan on using a smaller .578"/.578" lift cam---and I am not exactly sure if I will have him port the exhausts any further yet or not . I really like the mid-lift flow numbers---they are very impressive the way they are now especially after he chamber ported them, and if I were to have Jim further port the exhaust ports I am not so sure that those mid-lift numbers would stay the same or shift to higher lift flow numbers which I really don't want, and neither am I quite sure I really need it. I am quite confident with Jim's talent and experience/abilities that he would get more of a gain out of the port rather than a loss, and when asking Jim about it I really appreciated Jim's honesty when he told me he could not honestly tell me how the flow numbers would truely end up. I have to wonder at what expense---from my wallet ("bang for the buck") and also the expense that the MID lifts might suffer for a HIGHER lifts gain especially with the cams I am using. I can just hear how old Foghorn Leghorn would put it;

"BOY, I---I SAY, BOY!!! ONCE THAT METAL COMES OWFF---I--I SAY, ONCE THAT METAL DUN COMES OWFF IT'S OWFF FOR GOOD SON, YA HEAYA ?"

I could offer a big discount on Dart heads. Jobber price (bare head) is $912.00 each. I could do a lot better than that. I'm not hooked up with AFR. I did ask AFR for a head I could experment on. They said yes but that was two years ago.

well it looks like the afr cnc 315 kicks most the other heads a--,even bigger ones but if they are inflating there numbers then what is the best choice. The local head porter (he is talented) in our area says he has flowed afr's and they are no better than a pocket ported stock head? I'm not sure what to believe, If afr's claims are true then basically up to .700 lift a dart pro1 345 won't come close to there 315 cnc head or will it even beat there as cast 305 cc intake head (i do find this hard to believe). I plan on purchasing a set of heads this winter,but i don't want to spend 2500 0r 3000 just to take my heads in to be flowed to hear they need another 1500$ worth of port work,they aren't close to their claim. I'm have no problem spending money, i just don't like paying TWICE. Smitty

articfriends/Smitty,

Well said! Yes, I like to go fast, and I like running decent performance equipment, but there will always be someone faster. I supposed if I wanted to go faster I could put a supercharger on it as a forced induction engine can cover a lot of the mistakes, and are much more forgiving than mistakes made by a naturally aspirated engine where I suppose air flow numbers are more critical. I am blessed enough with what I can afford, and for what I have got, and the money spent I believe my heads are good enough. Besides, my life isn't dependent upon how fast I go on the water and I have other financial commitments and I certainly don't want to pay twice either. I just want to be in the "ball park" and my own .02 is that I think I am close enough.

Ahhh the numbers game .the is no set way to get the flow #'s. different vac and diff plates etc.


Most of the drag racers I see use the dart 360 and some are starting to use the Pro 1's reason?mayby there cheaper?

I was thinking about adding aluminum AFR 315 cnc heads to my 5000efi's but want to run 87 octane, what compression ratio should I use? would you recommend a cam change?

Man, this is one confusing thread. This is a perfect opportunity for one of the mags (Hotboat?) to do a build up series on. There are enough of us with 500efi's who want more power, but it seems no one has really done any extensive dyno work on one to see what bolt-ons will give a good power increase besides boring to a 540. I would love to know what the limitations of the stock fuel system are.
Anyhow, back on topic, have we decided what AFR head will work best?

I should have a customer with some dyno numbers real soon on 502 CID that just underwent a head and cam swap. It has a set of the small canfields, unported with factory valve job and a mild hyd roller stick designed for 5400 max rpm. I'll post the numbers as soon as he gets the dyno problems lined out. This package is conceived to be a bolt on type kit for carbed 502's and HP500 equiped boats. Dyno numbers are with 89 octane and wet CMI's so should be pretty close to running conditions.

Chris

I have not personally used these pieces yet, but know some reputable builders making very good #'s with these heads. I dont sell Profiler Heads, nor am I affiliated, but they are worth a good look.
http://www.profilerperformance.com/bbc-heads-174.html
Bob

I will be having my naturally aspirated 565" engines dyno tested with the 357cc AFR cnc ported heads that have been chamber ported by JimV sometime between November and Febuary by Dave Wessledyke of WESCO. I will be able to use my Stellings full length tubular headers during the tests.