strength of the 4.6 SOHC

[geoffsgt]

I have an 03 GT and am about to put a 9psi Kenne Bell 2.1L interooled s/c on it (most likely with the 90mm meter, 75mm TB and Big Tube kit, and their cold air intake) . I see a lot of people here have done this on the stock internals, so I'm not so much worried about that. What if I ever wanted to up the boost, or switch to the bigger blower? What would need to be upgraded? What are the weak points in the 4.6L SOHC engine under boost?

Also, what about the clutch, 3650 tranny, and rear end? I figure I'll need a better clutch when I get the supercharger, but will the transmission and rear end hold up to hard launches at the strip? My car only has about 30k miles on it, but it was my first manual transmission car, and i drive like a madman - for example, my apartment building is on a 50mph 2 lane street, so every time when I leave, i'm pretty much flooring it and powershifting into 2nd (whether I have to or not) - so the gears have been messed up a little.

I've read in atleaset 1 magazine that the motor can "safely handle up to about 400hp." Is this true, or does it have more to do with compression ratio's and/or boost? ie, if i make say, 380rwhp with the blower above, and put in a serious cam and maybe some other mods, and break 400rwhp, do I have to start worrying about it? Or is it mainly just if I up the boost?

 

[timeless2]

What are the weak points in the 4.6L SOHC engine under boost?

The entire rotating assembly. Revs kill.

Also, what about the clutch, 3650 tranny, and rear end?

Clutch will be fine...for a while.
The TR3650 will support the numbers you'll produce with 9 pounds--depending on how you treat it.
The rear...subject to scrutiny. Don't place any bets on it.

I've read in atleaset 1 magazine that the motor can "safely handle up to about 400hp." Is this true, or does it have more to do with compression ratio's and/or boost? ie, if i make say, 380rwhp with the blower above, and put in a serious cam and maybe some other mods, and break 400rwhp, do I have to start worrying about it? Or is it mainly just if I up the boost?

In the experiences I've witnessed, the combination of boost AND revving is what kills the stock setup more so than boost alone. With a conservative tune and moderately aggressive driving, there is no prominent reason keeping you from 400hp with decent longevity.

 

[madmatt]

TUNE TUNE TUNE

I cant stress it enough. Get someone that knows what they are doing to tune the car on a dyno with A/F readings. Also, Timmy was dead on. The only thing in the block that isnt really weak is the crank. Some upgrade to the cobra forged crank, but Ive never seen a GT crank fail, maybe someone else has.

GET IT TUNED

As far as the trans and rear, those are the kinda things that IMO, you dont skimp on when you buy a 5k dollar supercharger. Expect stuff to break with 400 hp, it happens eventually if you drive it like its meant to be driven. Some are lucky, some arent.

TUNE!!!

 

[Ernad]

you're gonna break stuff, I can tell




you will probably want to upgrade your rear with 31s after you smash it into pieces

 

[sgarlic]

As said, don't over-rev it, don't disable or adjust the rev limiter, and use quality (highest octane in your area.. shell, chevron, mobil) gasoline.

I'd probably throw a wideband on, and check it out for myself the first few times I got on it, and perhaps bring it somewhere to have dyno'd just to see the A/F graph, but KB specifically says don't **** with their tune..

 

[DBMSTNG]

the 2.1L KB is overkill for the stock block. a 1.7L will be enough to max out the stock block. cylinder pressure kills rods and detonation kills pistons.

you'll want a clutch with more capacity. the TR3650 is not weak, but it's not durable under the conditions you are/will be driving. get a TKO 600.

as far as the rear end, it depends how sticky the tires are. with sticky tires, you are putting alot of stress on the car and the rear end will eventually let go.

 

[geoffsgt]

the 2.1L KB is overkill for the stock block. a 1.7L will be enough to max out the stock block. cylinder pressure kills rods and detonation kills pistons.

The 1.7L was replaced by the 2.1L. Same boost, lower blower rpm's is the advantage there, from what i understand.

you'll want a clutch with more capacity. the TR3650 is not weak, but it's not durable under the conditions you are/will be driving. get a TKO 600.

Whats the price on one of those? If I was going to need a new tranny, I was gonna go with the T56.

as far as the rear end, it depends how sticky the tires are. with sticky tires, you are putting alot of stress on the car and the rear end will eventually let go.

It'll have Nitto DR's on it.

 

[DBMSTNG]

The 1.7L was replaced by the 2.1L. Same boost, lower blower rpm's is the advantage there, from what i understand.

cool, didn't know they stopped shipping the 1.7L

Whats the price on one of those? If I was going to need a new tranny, I was gonna go with the T56.

i think the TKO 600 is about $1500 and can handle a rated 600ft/lbs of torque. the T56 is nice, but expensive for the stronger Viper spec. the Cobra spec is only good for 450-500 rated ft/lbs if i remember correctly.

It'll have Nitto DR's on it.

you'll blow the rear end launching hard multiple times on DR's.

 

[QDRHRSE]

I'm about to install a very similar set up. If you want to keep the engine in tact don't rev it past 6k with the KB and by all means do not exceed the 9lbs of boost. If you do be sure to use race gas. The cylinder pressure after 9psi is too much for the rods....that's how I got a smokin' deal on my KB. If you rail on your car as hard as you say I recommend a vortech rather than a KB. The low end tq produced by the KB will cause you to leave drivetrain parts behind everytime you leave your pad (according to your description). The twin screw blowers are a different kind of animal. They produce instanf boost.

 

[PonyboyIsaac]

yep i've had mine on for well over a year now and havent broken anything yet. The first thing that is going to go on my car is the clutch i'm pretty sure, sometimes it chirps like a cricket after i'm hard on it(think its the throwout bearing). Rearend is still good but i havent had drag radials or slicks on it ever, i run goodyear f1 gs/d3s 315s on the rear and they light up in smoke so the rear hasnt been stressed to much. But like they already told you, get your a/f ratio checked right when u install it just to be safe. Heres a vid of my dyno just to entertain ya http://www.youtube.com/watch?v=JFcM9P-ZSO8

 

[geoffsgt]

Yeah, I'm more than willing to adjust my... driving habits for the sake of my car. I have never even considered raising the rev limiter on my car.

Ponyboy, that hood is pretty badass. Is that a Mach1 hood, or custom made? Does the KB stick up through it? Got pics of it closed?

 

[PonyboyIsaac]

Yeah, I'm more than willing to adjust my... driving habits for the sake of my car. I have never even considered raising the rev limiter on my car.

Ponyboy, that hood is pretty badass. Is that a Mach1 hood, or custom made? Does the KB stick up through it? Got pics of it closed?

why yes i do, time to whore
yeah its a carbon fiber mach 1 hood with a plexi glass window
heres some pics of it when the hood was still unpainted

here it is painted

 

[GDawg]

I've always heard 400hp is the limit for our stock engines... Guess I have to spend more money...

 

[SaleenGT2001]

400 is conservative. they should hold AT LEAST 420. i've seen stock engiunes holding 480 with no problems. they are a time bomb but they are still running