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View Full Version : What psi/rpm do stock internals crap out?



danman
10-08-2005, 10:39 PM
He guys I am thinking about going with the roots blower, and I'm wondering what hp/psi/rpm do stock internals crap out at? Such as pistons incinerate at xx boost level, or rods snap at anything over x,xxx rpm.

Thanks

Mike8675309
10-08-2005, 11:41 PM
roots blower? If you have an SC, you already have one attached to your motor.

Engine RPM redline is like 6800. You won't make much power though past 5600rpm without some head mods and cam.

Redline for the Eaton M90 is 15,000 rpm. You can get titanium shafts and the internals reworked for reliable performance above that.

lube70
10-08-2005, 11:45 PM
The engine will not make power above 4,500 RPM and will only drop after that. The red line on an SC is actually 5500, not 6800. 6800 WILL blow up your engine.

The roots style blower is on SC's from the factory. Without any exhaust or intake mods, the most you can do is a 5% pulley and some underdrive pulleys.

Other than that, you're asking from trouble.

I suggest doing some homework VIA the search function here before doing any mods or attempting any work on the car.

Don

danman
10-09-2005, 08:59 PM
K sorry guys. I'm not that dumb. I own a v6 stang, and I know how some sc guys are opposed to the roots swap. I didn't want to start a flame thread or something.

I'm v6fordmustang95 on v6power.net. I'm at 172rwhp/227rwtq with my single port n/a #'s, and I'm thinking on going roots blower since not many stangs have it done, and I dont really want to go centrifugal, or turbo.

So you would not suggest anything over a 5% pulley for the stock internals? What is the weakest part of the sc motors other than pistons? I know the head gaskets can cause problems since theirs so many coolant ports.

Stock boost is what...8psi?
Thanks guys

rlong
10-09-2005, 09:07 PM
i think stock boost is around 12 to 14 , i have revved mine to 6500 by accident and it didnt blow up but mostly they lose power over 4500 unless you got good exhaust and ported heads

nickleman60
10-09-2005, 09:53 PM
do you plan to bolt the blower to your mustang v6 block or are you using a sc motor? i don't think the mustang bottom end is as strong as a sc's.

x182dan
10-09-2005, 10:26 PM
if you wanna make it last use a compete sc motor. you will need a lot of sc specific parts if you wanna do that swap. but if done right a sc motor will last a lot longer than a 3.8na motor

lube70
10-09-2005, 11:33 PM
I thought you were using this on a stock SC. I didn't (actually you didn't mention it) know that you were using it on a Mustang. The Mustang Bottom end will not tolerate the pressures.

The rods and crank are not made to withstand the boost from 10-12 PSI.

I would suggest getting a larger pulley (IE: lowering boost pressure) or going with a centrifical blower.

The problem with early SC's (early 89's were recalled for this) was the cast (DURACAST) cranks. They wiped out or cracked after only a few thousand miles.

Hope this helps and makes things easier. I would suggest using an SC block and heads. This solves the WHOLE PROBLEM!!!! (and is easier and cheaper!!!)

Hope you get going fast soon!!!


Don

rzimmerl
10-10-2005, 11:15 AM
isnt XR7Dave is making like 21psi on a stock SC bottom end with the AR, and making over 400RWHP

danman
10-10-2005, 02:12 PM
Hmm whats different about the SC heads over the stock n/a stang heads?
The reason I ask is that I already have BV single port heads with 3angle...bla bla bla that I dont want to try to sell and lose money on.

Also I will probably be using an SC block that I will take apart and shotpeen/polish the rods, and probably reuse the stock pistons unless there are some forged pistons that can be used with stock rods for you guys.

My goal is a solid 300rwhp for now. If I break into the 12's I will be happy. I was thinking of going with a custom front mount IC, because I would like to do the lowest boost possible with the highest efficiency. I know its more expensive, but its less stress on the motor.

What boost with my engine mods do you think I will have to go with to get to 300rwhp?
BV heads w/3angle ported/polished, ADJ 1.8 rr's, 215/223 cam, CAI, Catless X-pipe, Mach1 mufflers w/turndowns, UD Pulleys, Stock TB halfshafted/polished, x-calibrator tuned, Aluminum DS

Those are just the mods that I would have after the swap (minus my ported intakes now, and other stuff that wont matter like clutch and shifter...)

I want to thank you guys for not jumping on me and there hasn't been one ounce of sarcasm yet (that I've picked up on) in this thread. I'm glad you guys aren't anywhere near 3.8mustangs level of retardedness.

Thanks,
Daniel

Mike8675309
10-10-2005, 07:35 PM
Only having the MN12 chassis to go from, 300rwhp won't get you into the 12's.

Stock pistons and rods are good enough for under 400rwhp, though I wouldn't try it if there are plans for nitros.

The main issue with the M90 vs the Vortec like chargers is the load placed on the crankshaft. There are folks running well over 500rwhp on the cast mustang crank. But the load on the crank is much less than getting 500rwhp out of a m90 would cause (if it could even be done). You'll want a forged crank when chasing HP with a M90.

Can't really estimate your power as unfamiliar with your parts. Close to 300rwhp though sounds close. Maybe 280? The newer MPIII blower from Magnum powers may achieve more with the same engine work.

Cooling passages are different in the SC head, and the deck is slightly thicker. If you search I think there was a discussion on split port heads on the sc block. problem is a intake manifold would need to be fabbed up.

Magnum Powers
10-10-2005, 08:07 PM
We have made 390 rwhp @ 5,000 rpm and 469 torque SAE on a Mustang dyno with a stock block Super Coupe engine running 92 octane pump gas with our new MagnaPortIII case and intake plenum @ 17.7 psi boost. With race gas or alcohol injection power would be more like 410 to 420. The power on the street is amazing even in the heavy SC chassis so in a Mustang it would be a killer. BTW that is more power then a stock 04 Cobra puts out. The heads had a mild port job just cleaning up the bowl area and taking care of that huge thing that stick out in the exhaust port. The cam was very mild with only 206 degrees duration and .512 lift.

The SC engine has a forged crank, more webbing in the block and the heads have a thicker deck and are stiffer then the heads on a Mustang. The compression is lower at 8.3 however some guys are making more power by upping the compression ratio. You might think about getting a SC crate motor from Ford, they are not that expensive. Give me a call for details.

Charles

Justin89SC
10-10-2005, 08:22 PM
isnt XR7Dave is making like 21psi on a stock SC bottom end with the AR, and making over 400RWHP

Would you know kind of AR or the model number of an AR for an SC. Im looking into them for a winter project....maybe. :D

Mike8675309
10-10-2005, 09:47 PM
I believe the Autorotor is the 1.7litre model. Search on user "XR7 Dave" and 1.7l and you'll find his posts of what he's been doing.

danman
10-10-2005, 11:46 PM
Cooling passages are different in the SC head, and the deck is slightly thicker. If you search I think there was a discussion on split port heads on the sc block. problem is a intake manifold would need to be fabbed up.

Do you guys have to do anything special to get the autorotor to fab up to your engines?

Also I have the single port head/intakes (mustangs 94-98 do) and they should be the identical to yours because I know we can use them on our blocks.

I saw something about the autorotor or MPIII had special intake pieces made that flow more air.
Sorry guys try to be patient I'm cramming all this in at once trying to see which way I want to go power adder wise, and this looks like a fun way to go.


You might think about getting a SC crate motor from Ford, they are not that xpensive. Give me a call for details.

Charles
I would get a crate motor, but I would really like to shotpeen/polish the rods, and I know there's got to be better than stock rings out there.

V8Supercoupe
10-11-2005, 08:34 AM
Engine RPM redline is like 6800. You won't make much power though past 5600rpm without some head mods and cam.

The engine will not make power above 4,500 RPM and will only drop after that. The red line on an SC is actually 5500, not 6800. 6800 WILL blow up your engine.

Are we talking engine only here, or an engine with an M90 on it? There's a difference. Surely an A/R/Mag 3, turbo'd engine can go farther than the M90.

Mike8675309
10-11-2005, 07:48 PM
A inlet pipe modification is necessary with the auto-rotor to get the intake and outlet pipes to attach. This modification is part of the kit from XR7 Dave. The MPIII requires the magnum powers inlet plenum I believe.

When I say intake manifold need to be fabbed, I'm talking about getting the supercharger to attach to the intake manifold and clear the hood. Not fabbed to attach to the heads.

The 3.8 block has some very specific valvetrain issues as well as piston velocity issues that provide a fairly hard limit to the max RPM of the motor. Where it makes power is a function of the blower being used and the flow capabilities of the heads/intake.

XR7 Dave
10-12-2005, 08:56 PM
With an M90 you can't make enough power to overrun the stock parts. With an M112 you might be able to run it up ok. I'd say 22psi and 6200rpm on pump gas is reasonable with decent valve springs.

T-bird4vr
10-12-2005, 11:53 PM
I'm at 22-23 psi with a stock bottom end and dalke's AR.
The thing kicks as. I wish I would have made it to the shootout since Kirt and Tony weren't running very fast.

danman
10-13-2005, 12:37 AM
With an M90 you can't make enough power to overrun the stock parts. With an M112 you might be able to run it up ok. I'd say 22psi and 6200rpm on pump gas is reasonable with decent valve springs.
Dang are you serious? 22psi on a stock bottom end? I wouldn't want to go past 15-17.

I already have suffiecient springs for the setup I think. They are .600's or something, but the M112 is the Magnum Powers upgraded blower?

So the Autorotor just needs a inlet pipe mod as in I need to buy the modded pipe in a kit made by someone or is it a mod I have to do myself like redrill holes for something to fit?

Thanks guys. I had no idea the stock stuff would hold out like a champ. You guys stock pistons are hypereutectic correct?

danman
10-13-2005, 12:42 AM
I'm at 22-23 psi with a stock bottom end and dalke's AR.
The thing kicks as. I wish I would have made it to the shootout since Kirt and Tony weren't running very fast.
I dont see in your profile it saying anything about your heads being ported, or having BV heads? Are your heads stock?

Also is your top raised? I've heard about the raised top mod piece, but does the 1.7 autorotor have a different top that is required? And the autorotor is a Compoletely different blower correct??

T-bird4vr
10-13-2005, 06:15 PM
I dont see in your profile it saying anything about your heads being ported, or having BV heads? Are your heads stock?

Also is your top raised? I've heard about the raised top mod piece, but does the 1.7 autorotor have a different top that is required? And the autorotor is a Compoletely different blower correct??

Ya it is a completely different blower, twin screw type instead of striaght postive displacement (it compresses some along with pumping).

Heads are stock, bottom end is a stock rebuild. The only thing done on the heads was a gasket match and a valve job. I do have a raised top, helps flow and gives a small buffer to the pressure spikes.

Even if you can get that pressure through an m90 the discharge temps would be very high.

Dalke probably doesn't know this but I swapped JS pulleys again.

And there is more stuff in my sig under cars for more pictures of what is going on if your interested.

V8Supercoupe
10-13-2005, 06:23 PM
Thats pretty frickin impressive julian. BTW, I have the identical car to yours, only a 5 speed. I am trying to get my heads done and get a new blower installed. But I am impressed your doing what you are with a stock motor.


Skip

T-bird4vr
10-13-2005, 06:58 PM
I'd like to get it back on a dyno Skip. The power in my sig was when it was running out of injector (42's) at 5k, I would assume with the AR it would continue to make more to 6k buy maybe not. I'd like to think it is closer to 350 but maybe not.

Dalke needs to come back to Lincoln so I can get it tuned again.

danman
10-13-2005, 09:17 PM
I'd like to get it back on a dyno Skip. The power in my sig was when it was running out of injector (42's) at 5k, I would assume with the AR it would continue to make more to 6k buy maybe not. I'd like to think it is closer to 350 but maybe not.

Dalke needs to come back to Lincoln so I can get it tuned again.
I take it your #'s in your sig was with the 1.7 AR?
Where can I find links to the AR product?

XR7 Dave
10-13-2005, 09:27 PM
I'd like to get it back on a dyno Skip. The power in my sig was when it was running out of injector (42's) at 5k, I would assume with the AR it would continue to make more to 6k buy maybe not. I'd like to think it is closer to 350 but maybe not.

Dalke needs to come back to Lincoln so I can get it tuned again.

Julian needs to go to the track so he can back up those numbers. :p

T-bird4vr
10-13-2005, 10:22 PM
Julian needs to go to the track so he can back up those numbers.

Ya I know.

90blkbrd
10-14-2005, 08:32 AM
Dang are you serious? 22psi on a stock bottom end? I wouldn't want to go past 15-17.

I already have suffiecient springs for the setup I think. They are .600's or something, but the M112 is the Magnum Powers upgraded blower?



Magnum Powers blower isn't a M112. It is an upgraded eaton M80.

Julian's HP and TQ was with his AR installed and not enough injectors.

Look at "XR7 Dave" signature at the bottom of one of his posts. He has a link to his email address. He sells the AR package. He doesn't have a website to his products but there is plenty of information on this website about the AR. By the way it is completely bolt on.

SCme94
10-15-2005, 08:01 AM
I wish I would have made it to the shootout since Kirt and Tony weren't running very fast.
Hey Julian....Why don't you take that thing to the track to get some numbers so you can back up your bench racing? :)

FWIW I have stock internals in my 94.