[ITowBoats]

has anybody looked into the grind on the 7.3 marine cam and compared it to the stock truck cam?

way back in time, little known to most ford used the 5.0L marine cam in the very hot boss 302. the cams were ground in such a way that would allow the motor to live very happy 5000 rpm all day long in a boat. it made for one crazy street engine.

does anybody know if its the same case for the marine cam in a 7.3L? I would think that it might since the operating range is 36-3800 rpm.

 

[gregrob]

Dirty Dave has a camshaft but he keeps it a secret pretty much, have no idea where he got the grind specs for it.

I'm sure if you go down there and beg him to let you purchase the latest edition of the DIsecret decoder ring he may sell you one. /ubbthreads/images/graemlins/shocked.gif

 

[444turbodiesel]

If you had a serial number from a marine engine, you could get the specs from IH, unless it was a Mercruiser custom grind.

 

[02Powerstroke]

even if the camshaft was used in a marine motor which ran at 5000rmps, the diesel motors components are huge wouldn't stand up to spinning at 5000rpm's at all. Camshafts arn't really related to how many rpm's the motor can handle, its more with the duration at which the intake and exhaust valve are opened and closed...

 

[jaybee]

I think the 5000rpms on the 5.0 gas burner was merely an example - not meaning he wanted to turn a 7.3 that fast.

And actually, the statement about a cam determining what max rpms an engine can handle isn't entirely true. Not only does the cam control the duration the valves are open, it also controls how fast the valves are opened or closed. Since valve float is usually one of the first concerns when bumping up the rpms, the cam grind is very important in this matter.

 

[SMOKINROD]

the last DI cam I got had the same part# as my last hypermax one it evan cam with the same cam card (info on the cam as far as the lift and etc.)

 

[Kanman]

Wouldn't a marine cam be designed to run at a fixed RPM? Hypermax cam costs $450 and is designed specifically to run with our trucks.

 

[ITowBoats]

i'm aware of that, its just part of the effect of the story. the design of the camshaft let the engine breath really well at sustained high rpm's. in a diesel's world, this would equate to more overlap during scavenging

 

[clux]

Maybe I'm worng, but wouldn't the gains in camming a torbocharged engine be pretty minimal anyway?
Seems to me you could do the same thing (and a lot more,easier)with a more efficient turbo.

 

[lukecline]

look at all the dodge big boys, nearly all of them are running aftermarket cams. They claim lower egt's and easier to spool turbo.

 

[ditch_dawg]

[ QUOTE ]
Wouldn't a marine cam be designed to run at a fixed RPM? Hypermax cam costs $450 and is designed specifically to run with our trucks.

[/ QUOTE ]

Having worked on marine diesels (15L-27L), not necessarily. If it was on a tug or barge yes definitely 1500-1800rpm all day long. Whereas a deep sea fishing boat definitely not, as it has a completely different duty cycle; haul ass to where you fish, troll, haul ass back. I can't vouch for the 7.3L marine bumpstick, but I can only imagine you wouldn't see to many of them pushing barges.

 

[75f100]

Anyone have the stock cam specs, that they would post??

 

[444turbodiesel]

[ QUOTE ]
i'm aware of that, its just part of the effect of the story. the design of the camshaft let the engine breath really well at sustained high rpm's. in a diesel's world, this would equate to more overlap during scavenging

[/ QUOTE ]

There's technically no "scavenging" with a turbocharged engine (at least not under load, when it matters) due to the enormous back pressure, and too much overlap will let the boost blow right out the exhaust, or in the case of a turbo with high drive pressure it will actually reverse the flow of air. Picture this, under load at 30PSI boost a stock turbo will have upwards of 60PSI of back pressure, what do you think happens when both valves are open at the same time? With a low drive turbo (like a QSSB) too much overlap will push clean air into the exhaust (I guess you could call this scavenging) wasting boost.

I'd look into higher ratio rockers before I did a cam swap, a lot less effort to install (even if you change the valve springs) and you won't give up low end torque.

 

[clamgulch]

I know very little about cams- but with a turbo diesel valve open overlap needs to be kept to a minimum for the reversion reasons stated. Also, the last time I checked into the marine cam, it was Mercury's grind, it is designed for up to 4,000 rpm, and it cost $1,000. I'm not sure a new one is even available since the 7.3 is now long out of production in the United States. I think it would be interesting to see one run in a truck though and I thought about doing it, but cost and availability were too much hassle for me. I wouldn't put it in the "cheap performance" category- it would be an expensive experiment and a PITA to install.

 

[RenoF250]

[ QUOTE ]
Picture this, under load at 30PSI boost a stock turbo will have upwards of 60PSI of back pressure,

[/ QUOTE ]

Where did you get this idea? I have seen it around and I THINK it is incorrect. Since the burned fuel expands you get a much higher volume of air out of the exhaust than what you put in the intake. I believe that the increased volume on the exhaust is traded for higher pressure on the intake. I am open to being corrected though.

 

[gregrob]

[ QUOTE ]

Where did you get this idea? I have seen it around and I THINK it is incorrect. Since the burned fuel expands you get a much higher volume of air out of the exhaust than what you put in the intake. I believe that the increased volume on the exhaust is traded for higher pressure on the intake. I am open to being corrected though.

[/ QUOTE ]

The stock turbo DOES have a 2:1 drive pressure ratio, and thusly would have 60lbs of back pressure at 30psi boost.

 

[444turbodiesel]

That's approximate since the drive ratio on a stock turbo is nearly 2:1 for fast spool up.

The cylinder pressure when the exhaust valve opens is obviously much greater. As the piston reaches TDC, most of the exhaust gas is gone but the cylinder pressure cannot drop below the back pressure until the exhaust valve closes. If the intake and exhaust valve are open at the same time (overlap) the pressure will equalize between the ports, if there is a large enough pressure difference and enough valve overlap it is certainly possible for a pulsation to enter the intake port.

 

[ITowBoats]

Here's the replacement parts listings for the t444e marine motor.

http://www.dougrussell.com/partscatalog/...ckNumberList=13,20,19,3,4,2,0,1,16,18,8,9,11,10,25,21,7,29,28,27,31,5,22,26,23,12,15,14,24,30,6,17

I think that in the pulling arena where these guys are running full tilt from the start, a cam which is ground for sustained high rpm, could be useful.

maybe BBunting could give alittle imput in this area