Monty

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.

dyno

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

liquid lounge

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

JimV

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.

PatriYacht

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.

Madmax

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.!

JimV

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.

Madmax

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)

KAAMA

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.

RLW

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