I have been told by a very reliable source that the 4.6L Modular engine likes to turn very high RPM's. I have always been worried about getting past 6000, but the source says, it likes to turn 10,000, and it really doesn't start making Ponies until about 5500...


Any Comments...Thanks

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97 Blk. ROUSH F150
Powerdyne Supercharger
SVT S.S. Headers
TurboMAX Dual Exhaust
4.10:1 Rear Gears
Superchips, Inc. Chip
MSD DIS-4 Ignition
Moovin and Groovin on new go-fast parts

 

Well, in general overhead cam motors like to rev more than pushrod motors, but I don't know about 10,000RPM... I sure haven't heard that. I know they ran a 5.4L for days at a time at redline with no problems, but being that my truck hasn't come in yet, I can't even tell you what the redline is



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-cm

 

FastAssRoush, the HP on the stock 4.6l peaks out at 4800 RPMS and the torque tops out at 3200 RPMS. Do you actually run yours at 6000 RPMS, if so for how long?

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99' F-150 XLT SC 4X4 ORP LS 4.6L K&N Air Filter Air Box Mod (3" intake from fender & silencer removed), Superchip, A.R.E. Cover, Duraliner bed liner, Rapidflow 3" single CatBack exhaust.

 

To get power at that high of rpm requires specific cams for the job. Not to mention heads and forged internals. I know of some guys who run pushrod 289s to about 10K rpm.
The problem with a motor that revs that high is that the power band is up there so getting power below say 5K is almost impossible. Turbos will give a broader power range, but there are many limits to how fast the rest of the system turns. IE, clutch, tranny input shaft, pumps and alternators.
Heck some early Indy engines Ford designed were very similar to the Mod Motor.

Birdman

 

BigRed2..

I haven't reached 6K yet. I usually get out of it at about 5500. Even though I have been told it likes High R's, it still concerns me.

I have 4.10's, so I get this high when I have Overdrive OFF, and I am at very high speeds.

However, when I do reach this point, the Truck feels like a rocket.>>>>>>>>>>!!!

Happy Holidays..All Comments Welcome.



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97 Blk. ROUSH F150
Powerdyne Supercharger
SVT S.S. Headers
TurboMAX Dual Exhaust
4.10:1 Rear Gears
Superchips, Inc. Chip
MSD DIS-4 Ignition
Moovin and Groovin on new go-fast parts

 

Dear FAR,

Just a few comments, I hope you don't mind....

You should *never* spin that engine beyond 5700 rpm. Not unless it's had the benefit from a complete rebuild, including different camshaft profiles, forged parts, and many other mods.

It is true that the *DOHC* version of the 4.6 engine *is* capable of turning 7500 rpm and more if the rev limiter is raised and appropriate camshafts are used, (though the alternator will give up before that!) but not the SOHC engines. You see, the DOHC motor, as installed in the Lincoln Mark 8 and the Mustang Cobra, uses some extremely high-dollar and completely different parts than what you have. The DOHC's get 6-bolt mains (not 2-bolt, not 4-bolt), they get *fractured* instead of sawn connecting rods (which are specifically for prolonged extremely high-rpm usage, as they eliminate most torsional movement on the small end of the rod), head studs instead of head bolts, and the list goes on and on and on. Very different engines, these DOHC's!

DOHC's also have computer-controlled multiple-stage intake runner systems, etc.

Don't get me wrong, you have a *very* nice supercharged F-150 there, a vehicle that most of us here would give just about *anything* to own! But I would say to forget thinking of higher rpm's, 5700 is the practical limit for that motor with a blower on it, I would say, and maybe 5400-5500 is more like it. Another very important thing to remember is that these factory electronic tachs can be *very* inaccurate. They can read high OR low, especially when you are accelerating hard in first gear, when that supercharged engine is gaining rpms so very quickly. You can be turning more rpms than indicated, or you can be turning less than indicated. Some of them can also be pretty darn close, so you can get any result ranging from fairly accurate to way off, by hundreds of rpms.

By the way, your engine makes power long before 5500 rpm, as do all other modular engines, so it sounds to me like your friend might have his info wrong, unless he's talking about a race-prepped engine. And in *that* case, a 10,000 rpm engine usually doesn't make any real power until at least 5000-6000 rpm, I would agree with that.

And last, neither your engine nor anyone else's SOHC modular engine will turn more than 5400 rpm, *unless* it has had it's rev limiter in the computer modified. (5400 is the rev limiter, 5250 is the WOT upshift point) As a matter of fact, they have more than one rev limiter, they also have a "no-load" rev limiter, which is at about 4500 rpm on most of them. That means that anytime the engine is not under a load, like when it's in Neutral, Park, etc., it won't turn more than 4500 rpm.

Good luck with that great truck, and I hope you have a very Merry Christmas!

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Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com

[This message has been edited by Superchips_Distributor (edited 12-21-1999).]

 

Thanks Mike,

That just didn't sound correct to me either. This guy owns a Mustang shop, and is used to working with the Cobra's. Makes sense.

You mentioned you read an article on the MSD box. Can you give me the URL, or point me in the right direction to find the article...

I am just about out of ideas on mod's to the Roush. I was thinking about different heads. ANy ideas??? I am also thinking about attempting to lighten the truck up. I have no idea where to begin, and this may not even be feasible. Any ideas there??

Thanks for the advice, and have a happy Holiday....


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97 Black ROUSH F150
Dallas, Texas
Powerdyne Supercharger
SVT S.S. Headers
TurboMAX Dual Exhaust
4.10:1 Rear Gears
Superchips, Inc. Chip
MSD DIS-4 Ignition
Moovin and Groovin on new go-fast parts