KEPP

Here's the facts you have many choices when it comes to cylinder head choices and how they are compared is critical. The "Old" antique method of cylinder head comparison is done with what is known as "Dry Flow" technology this measures air flow only. Well we all know your engine has air&fuel mixed running through it. So while air flow only numbers can easily be distorted (Similar to Dyno results) The real measurement for how well a cylinder head performs is not based on air flow alone it is accomplished on a "Wet Flow" testing system. This method measures air&fuel like mixture as it travels through the cylinder heads. Anybody can get good dry flow #'s but Wet flow numbers indicate the truth. I can tell you that in a comparison like this the Dart PRO-1 cylinder head is a hands down winner. But this is just the start here's where the real value comes in. First consider the folks that use the heads. Our company history is rich with over 37 World and National championships. Ourselves, Chief Engines, Tyler Crocket, Paul Pfaff, Sterling Performance, Scott Shafiroff, and Reher Morrison just to name a few professional engine builders that use and demand Dart cylinder heads on their engine packages, all of us have come up with the same conclusion. The Dart Pro1 "as cast" cylinder head has out performed the AFR cnc cylinder head on the dyno by 10-20hp...Horsepower is what you want correct? Not to mention that there were big machining savings to you the consumer. On the Pro1 heads we as well as the other engine builders take them out of the box, machine the head down to the chamber cc that we wanted and simply put the heads together. The AFR heads had to have the valve guides honed, valve job, surfaced and then put together. At the end of the day the head that produces the most power and is the best finished product for your application, "WE" believe is the Dart PRO-1.

KAAMA

If the HP number differences are in fact true between the Dart Pro-1's and the AFR's, then I guess you can't argue with that, but wasn't it Ken Sperling who brought "Wet Flow" testing/research to AFR back in the mid 1980's??? That was a long time ago, but maybe things have changed at AFR since then.

I don't mind being the "fall guy" from time to time, I am just a weekend warrior....so, don't pound on me too hard.

69-CHVL

Hi guys,

My Gen 6 454 has the GMPP "502" heads with the 2.25/1.88 valves, and I have the matching GMPP "502" intake that IMO, fits the roval heads better than anything I've seen. Running the Lunati Voodoo 231/239 .6/.6, with the Crane lifters. I estimate my power to be around 525-540.

What kind of power would just bolting on a set of AFR 305's give me, any idea???

redcorvetteman3

OK now I know we have allot of different oppions but help out a newbee. I have a 4150 stinger V hull a pair of merc 420s borg warners and 1.5 TRS 23 pitch mirages top speed about 55 . Getting ready to upgrade motors most builders say no blowers on that heavy of boat how much motor can I build into the stock 4 bolt blocks before I must go to a dart or merlin block? what bore? and what stroke? . What heads, cam, intake and carb should I be looking at? Would like to cruise around 50 top out in the 80s. thanks

KAAMA

Much of it depends on how much money you're willing to spend. Is that Stinger you own a 41'.5" length hull???

Depending on the size/weight of your boat you're going to need a LOT of power to hit 80mph from where you're at now and unless you put some kind of supercharger on your 454cid engines you're going to be hard pressed to get it. Your 4-bolt 454cid blocks are strong enough to handle the superchargers, but it's your TRS drives/tranny's that will be the weak link with supercharged power.

Something that will help a lot is a good CNC ported head design...whether it's a Dart or an AFR.

I once had a pair of 454cid engines bored .060" (468cid). The blocks were bore notched and I was using the Dart cast iron oval port heads with 2.30" intake valves and the heads were ported, Dart single plane intake manifolds, 9.5 comp ratio, 850cfm carbs, solid/mechanical roller cams, Stellings full length tubular open headers that were dyno'd at 600hp @5500rpm. It pushed my heavy 32' Active Thunder with TRS drives, BW Tranies to about 88mph with very light fuel and one person in the boat. These engines were built in 1994 with an old head design compared to today's heads which are much further in technology since then.

If you're looking for some help with an engine/cam combination for your size/weight of boat, then someone who I would recommend is RMBuilder/Bob Madara of Marine Kinetics in N.Y. (585)654-8583. He's an honest, stand-up guy with years of marine hi-perf knowledge. He can get you the correct cam and Dart Pro-1's or the AFR heads, etc.

redcorvetteman3

Thanks for the help .This 4150 is the 39 stinger flat deck hull with intergrated swim platform. I'm going to go with 498ci, alm dart pro 1 cnc heads. Builder guaranties 625 to 650 hp @5000 rpm the sales brochure says the boats weight is less than 10k without motors. THANKS Mike

KAAMA

Oh yes, now I remember the old 39' Stinger. You've brought back some interesting memories! Back in the early-mid 1980's I used to see one at a local marina in St. Joseph, Michigan. It was all red and had a pair of Merc 400hp Cyclone engines in it with the old stock cast iron Merc exhaust system with thru hull exhausts.

The same guy owned it for many years. I remember hearing him complaining about it not being very fast and he thought with Merc 400's it was going to be a rocket, but it only plowed thru the water. With that kind of power he could not get the hull to break loose and make the boat ride on top of the water.

So, he had some guy install bigger cams in the engines, single/open plane intakes and Holley carbs, but didn't replace the stock Merc cast iron (junk) exhaust (He needed a good breathing aftermarket exhaust system to let the engine breath with all the other mods he did), but I always saw it with the same exhaust.

It turned out he wasn't too happy with the results....very rough idle and died a lot while shifting, the boat did not go any faster----actually, I think it went slower with all the mods he did and he eventually reinstalled the stock Merc cams back into the engines.

I remember a friend of mine who knew of some other guy that owned a 39' Stinger with Merc 400's in it and he eventually had them upgraded and dyno tested to something like 475hp back then and GIL aftermarket exhaust manifolds and it only helped a little....certainly not as much as he was expecting. It takes BIG power to get those 39' Stingers moving well.

Back then, offshore hi-perf pleasure boats just weren't that popular like they are today. During that time, we were pretty much limited to the technology of factory GM cast iron head castings and didn't have much of a selection in aftermarket head options, superchargers had not made their way onto marine engines yet, and there was no such thing as a hydraulic roller cam. I remember people putting cams in their engines that were too large and watching the engines die the second they put the boat in gear as they tried to back away from the dock. Pretty interesting days back then.

Anyway, it sounds like you've got some decent heads. Just make sure you have a good cam in there too!...hope it goes well for you. Have fun.

fantastixvoyage

Hey Mike make sure you contact my guys before you decide on any engine builds. The place is ran by Ed and Joe of Sterling fame. Unmatched quality and killer pricing.

feel free to hit me up if you got any questions

formula 382 sr-1

So what heads are the best for a hp500 ?

Nordicflame

I've heard through the grapevine that the "new 2008" Dart Pro1 heads unported out perform the CNC ported AFR counetrparts with all else being equal.

Has anyone else heard or witnessed this?
Thanks
Dave