High RPM 4.6, how high can you go?

midnightdriver · Feb 8, 2010

My buddy and I were throwing around the idea of instead of building my 4.6 into a FI engine. Instead try to spin her out to 7500 or 8000 rpm.

Do any of you guys spin that far out?

I plan on forged internals and ported heads with all the goods, set of cams and a good tune. But do you guys think it could be done?

I love the sound of high rpm race engines and I think it would set my car apart, cus I don't need 500 plus hp. Just want something a little different.

Thanks

Winters98GT · Feb 8, 2010

midnightdriver said:
My buddy and I were throwing around the idea of instead of building my 4.6 into a FI engine. Instead try to spin her out to 7500 or 8000 rpm.

Do any of you guys spin that far out?

I plan on forged internals and ported heads with all the goods, set of cams and a good tune. But do you guys think it could be done?

I love the sound of high rpm race engines and I think it would set my car apart, cus I don't need 500 plus hp. Just want something a little different.

Thanks

No

ran260gt · Feb 8, 2010

Winters98GT said:
No

sneaky98gt · Feb 8, 2010

I think 98cobra281 is going to spin his out to 7000 after his new cams. That's the highest I've personally heard of on a 2v.

40oz · Feb 8, 2010

I've been thinking about doing the same thing for a while now.

I think it'd be pretty easy physically. You wouldn't even have to change the internals to spin it to at least 7 grand, seeing as the only relevant diffference between an N/A Cobra and a 2V is the crank, regarding the guts. Ford kicks up the fuel cut quite a bit when you buy the power pack for a '05+, but they don't put forged rods in there for you, so I think it's clear they think the parts are strong enough. I don't think I've ever heard of a rod tearing in half because of rpm, but I've seen pics of more than one engine destroyed by detonation. And at 8000 rpms, I don't think there is time for detonation.

The only real issue I'd think would be breathing. Ported heads with lighter aftermarket valves and heavier springs would probably be a minimum. You have less time to get air in and out, so you need all the help you can get, but you ought to be able to push the torque peak north quite a bit with the proper cam.

Horsepower is torque times rpm, so if you can breathe at higher rpms you will make more horsepower even if you don't make more torque than stock. The upside is that you'd get a wider powerband by increasing the breathing, and there's no reason to stop spinning it at 6200 if you're making torque up there. Steep gears would let you use that power and offset the penalty you're going to pay down low.

04GTMustang · Feb 8, 2010

if you wanted to spin those rpms you are gonna spend tons and tons and tons of money if you can even achieve that. Im talking about the car not being streetable because of how crazy that cam and head setup would have to be.

if 8000rpms is what you want i suggest getting a bigger bore and a shorter stroke motor. or just buy one of them rotissary motors with the triangles lol

the longer the stroke at those rpms the more that can go wrong

AntiRice98 · Feb 8, 2010

A good friend of mine shifts at about 7200 when he races. He has a fully built 2 valve. He maintains peak hp till 7k then starts to drop a little

98COBRA281 · Feb 8, 2010

sneaky98gt said:
I think 98cobra281 is going to spin his out to 7000 after his new cams. That's the highest I've personally heard of on a 2v.

yup

hoping to spin her to 7000-7200

it pulls like an animal until it hits the 6200rpm limiter now, i dont think ill rev it to 7k until it gets retuned....

midnightdriver · Feb 8, 2010

The main reason I ask is I was looking at the crower cams website and they have a "low lift" cam that has an rpm range of about 2,000 to 6750+rpm.

Mr. Rustypwnz · Feb 8, 2010

i know there were a couple F/S nmra cars with only rods, ported heads/ cams and lt's and some other stuff, making peak power north of 7500rpm, with cast cranks, so you should definitely be able to do it, lots of air flow, compression, fuel, and LARGE cams and it can be done..

98COBRA281 · Feb 8, 2010

yeah i do have forged I beams capable of 7500rpms

nickmckinney · Feb 8, 2010

7000 is easy, 7500 is a bit more expensive but not too bad and can still be somewhat streetable (like an old school Boss 302 with a 4.56 gear and no overdrive was streetable). My personal new motor is being built for 7500.

9000RPM has been done on a full race 2V BTW and I know of a couple being built for 9500RPM with the TFS heads.

98Cobra281 you got the motor fired with those new cams?

98COBRA281 · Feb 8, 2010

nickmckinney said:
98Cobra281 you got the motor fired with those new cams?

yup! its runnning great and pulls way harded harder then before!!! i cant wait to rev it out, and get some new numbers and track times!

BurningRubber · Feb 8, 2010

I wouldn't mind having a 7k N/A 2v.

I imagine it could be easily done with just a Cobra crank, great rod bolts, ported PI's or aftermarket, and something like a Comp 270-278.

A buddy of mine spun his stock bottom end 2v with Comp 268's to 7,200 on nitrous until he obliterated the intake... engine was unharmed, though.

bhuff30 · Feb 9, 2010

Sure, you could spin it that high, but why bother? We all know that torque is what moves you and makes a car fun to drive. I only spin my 2.3 to 5500 and run some descent times with half the displacement!

It is quite expensive to build and engine that likes high rpms and make good power up there. Then, you still have problems, like the flywheel cutting your toes off and finding a transmission that would be willing to shift up there (because a stocker certainly wouldn't be happy!). You'll be a lot happier in the end if you build for torque. Get forged shortblock, a KB, meth injection and the smallest pulley you can buy. You'll have a hell of a lot more fun for less money.

Mr. Rustypwnz · Feb 9, 2010

98COBRA281 said:
yup! its runnning great and pulls way harded harder then before!!! i cant wait to rev it out, and get some new numbers and track times!

yeah get a vid, and a run to 7k lol

NerdKrusher · Jul 13, 2021

Don't even think about doing this unless you are willing to spend.

$5k on bottom end.
$5k on top end.
$3k on exhaust.
$5-10k on suspension and chassis.
$3-5k on drivetrain.
$1-2k on racing seats.
And that's not even including the tune!

I know this, because I'm already in the process of doing this myself.

I'm almost halfway there myself.
Just wanted to be realistic for ya, by all means if this is the path you want to go down, do it.

But if you don't spend that $20-30k on your car and motor. Kiss it goodbye!

Oh... and it will never be street legal, if you do everything to max power. Hope you realize that. But I have seen 500-600 hp N/A done with a 4.6 2v. You can look up the video on youtube.

High RPM 4.6, how high can you go?

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