F&PB article on AFR heads
 

I finally had a chance to read the article and although the comparison was not a simple head swap, in some ways it makes more sense to change the whole intake-head-cam package because that's what you have to do in real life. The stock heads and intake are not going to work with the solid roller cam they used.

I think the best way to evaluate the stock GM package versus the AFR package is to estimate volumetric efficiency from the reported HP figures. This is more meaningful than comparing flow bench numbers.

Stock - 530 HP @ 5500, ~88% volumetric efficiency

AFR - 700 HP @ 5500, ~100% volumetric efficiency

Can't complain about 100% V.E. I guess the question is, "Can you live with a torque peak at 5000 RPM in a boat?" The test boat was a 21 footer so low end was not an issue. The speed increase of 17 mph tends to back up the horsepower claims.

I'm looking forward to hearing results of these heads on a 540 or larger displacement with a hydraulic roller cam.

that just goes to show that supercharging is not the only way to get a good speed increase.

I think the AFR heads have the exhaust port raised ,so this will change where your exhaust exits the transom or change the tail pipes.

Hey Tomcat....

for those of us that can't find that magazine cause they live in a hick-town :rolleyes: can you give me a quick overview of the engine? Cubes? Cam? Compression? Intake?

Thanks.!:p

Madmax: They really didn't give much info in the article.

The base engine was a 502 GM crate engine with GM Performance castings (rectangular port). They don't say iron or aluminum. Compression ratio of 8.5:1. 530 HP.

A mild street mechanical roller (254/260 0.660 lift), a Victor Jr. intake and a set of fully CNC ported AFR 315cc heads with the tulip valve upgrade. 741 HP.

H2Xmark: It's the RPM that's the problem. I love the sound of a 6400 RPM big block as much as the next guy, but I don't really want one in my boat. I'd rather have that much power @ 5200 RPM with 7 psi of boost.:D

I am getting ready to build a 540 with AFR heads. This will be a 5500 rpm motor with durability being paramount. 9:1 compression and hydraulic roller cam.
All out HP and Torque is not the criteria.
If you go to the AFR website, they give you some flow numbers on some of their heads. What caught my eye was the 305 "CNC Chamber" heads. Not to be confused with the 305"As Cast" or the 315"CNC Ported" heads.
The 315 "CNC Ported" starts out as the 305 "As Cast" head. The 305 "CNC Chamber" head outflows the 325 "As Cast" head until it hits the .600 lift mark. I really don't see myself going much past that valve lift number anyway.
The 315 "CNC Ported" is only about 4% better than the 305 "CNC Chamber" head.
Is that 4% worth another $750 for a fully CNC Ported head?
Is the 305 to small for a 540 motor? Wouldn't the port velocity be better with the 305 head?
Does anyone have any input in regards to intake volume requirements on a mild 540?
Thanks for any replies.
Russ

I'm dyno testing my 540's this Friday with AFR 315CNC heads, Crane 741 hyd roller, Holley 850, Victor Jr intakes, etc.

I bought the heads bare with nothing more than the CNC work and copper-berrylium seats installed. I used Del West valves, D/W titanium retainers and locks, and Isky (actually PSI) Tool Room springs, with Crower stainless steel rockers.

We flow tested the AFR 315 CNC's on a Superflow and with Manley Extreme Duty valves the results were within 5 cfm or so of AFR's claims. Some were a little lower, some were a little higher.

I ended up going with Del West Inconel exhaust valves, and D/W stainless intakes, which we put a 30* back cut on. Retesting showed and improvement in the intake flow as much as 20 cfm at most lifts.

I built my engines for the most area under the curve between 2000 and 5500 rpm, with reliability and durability being more important than peak power as well. If you're interested, I'll post the dyno results this weekend.

Monty,
I was hoping you would respond. I have done my share of searches on 540's and your name always popped up. I have been following your replies and posts.
I find it interesting that you are using a Holley 850 carb. It seems that most builders want to use a 1050. I was thinking a 950 would be a good choice.
Did you machine in a wide contact area on the exhaust seat for improved heat transfer?
What was the reason for the copper beryllium valve seats?
Is it for both the intake and the exhaust?
Would you share what cam you are using and it's profile and your compression ratio?
Thanks!
Russ Withiam

This must be the winter of "540s"!I'm building one also.315AFR CNC,741 cam but efi instead of carb.HP500efi platform so wanted to keep the efi system.I'm going to try 9.2 cr,ordered JE pistons with 11cc inverted dome.With al.heads i think that ratio will be fine.Will post dyno results later.Monty,are you installing the cam advanced? BOB

This should be a great combination, as you noted there is not a big advantage to the 315,325 when using less than .60 lift and so their advantage is really in the 5000+ rpm range. The 305's will make good torque in the 3500-5000 range , I believe AFR recos the 305 as cast or chamber heads for 540's unless it is an all out race motor , talk to them about your cam choice/combo.

Yes we are interested :)

Russ,

Yes, the exhaust seats have widened margins. As with the wide seats, copper-berrylium aids in heat transfer and is also more durable. They were installed on both the intake and exhaust.

The cam is the Crane 741 hydraulic roller, .610"/.632", 234/242 @ 0.050", 112 LSA. Compression ratio is 9.0, so I can run it on lower octane if that's all that's available at the time.

I debated between the 850 and the Dominator's, but I just felt that for my application and setup, the smaller carbs would be a better fit. I'm sure I'll give up a little hp during the last couple hundred rpm of my operating range, but below 5000 or so, I should see better response and economy. At 9500 lbs and with TRS drives, I know it's gonna be difficult for me to reliably get the boat above the low 70's, so that's what I built it for. Obviously more power would do it, but at the expense of reliability and durability - I don't want to have to worry about blowing a drive everytime I go out.


Bob,
The 741 cam already has 5* advance ground into it. I installed them a couple of degrees retarded so that it would be closer to 110-111 ICA under operation (to account for the slack in the chain and valvetrain). I give up a little torque below 3500-4000, but gain hp in return above that. I mainly did it to make life a little easier on the drives.

where is Kaama???he's been there done this...I was at his dyno pull he made 699 hp at 5700 if I'm not mistaken. I think the #'s for the motor in the article are a little optomistic for a drivable pump gas motor with no blower.....my .02

Just thinking outloud.....if the exhaust flows the insane #'s claimed by AFR, my first inclination would be to back off the the exhaust seat timing and take advantage of the bump in cylinder pressure...not to mention a better idle and low rpm manners....hell, with those kind of flow #'s, with a scavenging exhast, you could go with less duration on exhaust than on the intake....why not? GM is doing it now on the new zL1. Sometimes it takes big nuts to defy conventional wisdom....dont know if mine are that big though:cool:

Just thinking outloud.....if the exhaust flows the insane #'s claimed by AFR, my first inclination would be to back off the the exhaust seat timing and take advantage of the bump in cylinder pressure...not to mention a better idle and low rpm manners....hell, with those kind of flow #'s, with a scavenging exhast, you could go with less duration on exhaust than on the intake....why not? GM is doing it now on the new zL1. Sometimes it takes big nuts to defy conventional wisdom....dont know if mine are that big though


Check the numbers. They use a cheater pipe that fools you into thinking the exhaust port flows more air than it does.

Liquid Lounge, I agree 100% with what your saying about backing off the exhaust lobe......it works!

One other note:

CNC heads look cool but so far I haven't seen any good programs for marine. The AFR heads have a intake venturi size of 90 % of the valve diameter. It looks great on the flow bench at .800 lift and works at the drag strip.
I have to use a head that has been cut for a 2.250 to make a 2.300 work for marine. My intake airflow numbers peak at .700, 400 cfm.

Same on the exhaust, they sell you on the airflow numbers at .800 lift. My marine exhaust ports peak at yup .700 a little over 300 cfm. So you say big deal?

Heres my braggin port:

.200.........143 cfm
.300.........209 cfm
.400.........276 cfm
.500.........295 cfm
.600.........300 cfm
.650.........301 cfm
.700.........305 cfm

No cheater pipe. If you want the cheater pipe number it's about 330 or 340 I cant remember.

Now, I can make the port peak at .800 with airflow numbers at 320 but I have to knock the short turn down and take a butt load of air flow at .4 .5 and .6 with it. No offence to anyone and this is not an advertisement, it what I have been doing for the last 20 years. My point is there is a huge difference between a drag race port and a marine port.

Sounds like good reasoning to me. I'm building a pair of 540's with AFR 335cnc heads and I've had the same ideas. I'm putting on 2 piece timing covers to make cam changes easier so I might just have to try it.

Not to steer the thread off course, but JimV, what heads would you reccomend for a 454 with a max of 5200 rpm? Would the heads you do work well for that or are the intake ports 2 big for a 454.?

thanks.!:)

Mad Max

It depends on the cam, compression ratio, exhaust, how much power you want to make, and how much money you want to spend.

A 454 dosen't need much port volume (no big secret there). If a two plane works better on a motor chances are the ports,cam, or both are too big. The cheapest way out is the vortec heads. They have a small chamber, oval port intake, and a small exhaust port that can be modified to flow respectable numbers. This is a great upgrade to a 330hp because it requires a flat top piston.

We have made 500 hp with the peanut port heads but the pistons have to be changed to up the compression ratio.

For big power with cams over .550 lift we use either a 310 port wedged to 290cc or a 345 wedged to 300 cc.

Your last sentence was exactly what I was wondering. So are your wedged heads GM rect ports, or do you start with something else (i.e. edelbrock, merlin vr)

I have the Dart Pro-1 310cc heads fully ported by JimV which he said are probably about 320cc's with 2.30" intake valves. My 540's made 699hp @5700rpm on Tom Earhart's dyno with a Ultradyne hydraulic roller cam 244*/244* on 112* lobes, HP950cfm Holley carb, @34* advance. I did change cams to a Crower hyd roller of 236*/244* on 114* lobes which is identical within a degree or two of the Crane 741. The Crower has more of a mild, much slower opening/closing ramp speeds than the Ultradyne that makes it a nice, gentle designed cam for the hydraulic lifter tappet. Crower told me it was a very smooth running cam that was easy on the lifters and valve train. Going to the Crower may have hurt me a little on power, but I didn't really care---I was looking more at the livability, longevity and endurance of my engines vs. hp. Anyway, the power I got out of my heads/engine combo was very respectable by any means.

However, it would still be very interesting to see Monty's dyno report on his 540's with the new AFR 315cc CNC'd heads.

Kaama,
Thanks for the reply. What are the valve lift numbers with the cams that you have used?
I am on the fence with either the AFR 305 "CNC Chambered" or the AFR 325 "CNC Chambered". Don't have the 325 flow numbers yet.
Russ

RLW - use the 325's!!

Mad Max

I have wedges for the Merlin VR and GM heads although I wouldn't recommend either one if your starting fresh. The Dart iron heads would be my first choice. They are capable of flowing as much air as their aluminum castings.

Lift on the Ultradyne was .601"/.601"

Lift on the Crower is .610"/.609"

I did NOT dyno the engines with the Crower cams. Another thing about the Ultradyne's is they have a much more AGGRESSIVE opening and closing ramp speeds.

I never water tested the boat with the Ultradyne's as I removed them and installed the Crower cams.

Keep in mind that I used a 1.8:1 ratio rocker arm on the intake side of the heads---1.7's on the exhaust.

My guess is that swaping from the Ultradyne's to the Crower's I may have lost 8-15hp on top-----just a rough guess. Like I said before, I could care less about the power loss when I switched to the Crower's. I just want the engine and compoments to live. Because of Ultradyne's aggresive, fast ramp speeds, they are very HARD on the valve train---something I did NOT want.

Some guys want every DROP of HP they can get out of an engine i.e. bigger cams----even solid rollers, high comp ratios, etc. My attitude is a little different. I like decent, mild idling engines that shift easy when you're trying to dock/slip the boat, or when the WIND is pusing you around, or when you're having to deal with the water CURRENT of a river, or when just manuvering around other boats whose captain's don't always know what they're doing or half in the bag from drinking, etc, etc. It's these kinds of situations that you can find yourself in that can get you into trouble FAST and a boat that idles well and does NOT die when shifting is what I prefer. Some dudes have such a HUGE, LOPEY IDLING CAM in it that it dies everytime he attempts to shift it can get pretty intense---especially when the engine dies and he's still coasting in a direction he no longer wants to go in and then when he starts the engine back up he usually over compensates each manuver cuz he's panicing then he runs into another boater or into a sea wall----that's when a guy doesn't look so cool anymore.

With those Crower cams, Crane Fireball Hi-6M ignition boxes, 950 Holley's, Dart single plane intakes, and MSD Crank Triggers, the boat in gear idled as low as @550-600rpm with a 32' Active Thunder and 32" pitch Bravo One 4-bladed props. Works good for me. :)

Mark,
was the cam in this thread actually the UltraDyne?

http://www.offshoreonly.com/forums/s...threadid=58079

Post 9
That may explain why it was still making power when passing the 5700 rpm mark.

Thanks,
Dave

Dave, to answer your question; "YES" it is. It was a difficult decision because of the costs involved, but I wasn't sure it was a good idea to run a dual pattern cam---so I went back with a split pattern cam---I must have changed my mind 15 times on which cam design to go with. The split pattern Crower was either going to help me or hurt me, but whatever it was either way it would only be by a very small margin I figured. Heck, I was even considering some flat tappet Ultradyne solid/mechanical cams----I still have those new in the box with Crower cool face light weight lifters.