Weak point of 2 valve 4.6 motor.. RPM?

OinkAodeOink · Apr 4, 2005

I've been wondering, just what is it that seems to kill the stock power adder 2 valve 99-04 GT motors? Is it high rpm, or simply a bad tune? From what I gathered, the rods seem to let go first, being everything else is in check. Now my question is.. Say I build a low RPM turbo setup..full boost by 2500rpm, max out around 5k RPM, would this in theory, keep the motor somewhat more safe, then a motor that sees 6k rpm? If it's as simple as detonation killing these motors, that can be kept in check with achohol injection or simply running very low boost levels, and an efficient turbo setup.

Im sure I would be content with 450 to the wheels ( for a week ) If I could keep it all in tact, by keeping the RPM's low, enough fuel, and safe of detonation, with a low amount of boost (under 10psi)

trinity_gt · Apr 4, 2005

OinkAodeOink said:
I've been wondering, just what is it that seems to kill the stock power adder 2 valve 99-04 GT motors? Is it high rpm, or simply a bad tune?

Mostly the latter from what I've read, depending on what you're after. I think the factory components are strength-limited to something like 500HP, in theory, but I'm sure there are 2Vs making that and more on stock internals...they just have very good tunes and live life on the edge. Keeping the engine from experiencing detonation is all about the tune, ensuring the quality of fuel and being realistic with the boost level.

From what I gathered, the rods seem to let go first, being everything else is in check. Now my question is.. Say I build a low RPM turbo setup..full boost by 2500rpm, max out around 5k RPM, would this in theory, keep the motor somewhat more safe, then a motor that sees 6k rpm? If it's as simple as detonation killing these motors, that can be kept in check with achohol injection or simply running very low boost levels, and an efficient turbo setup.

Im sure I would be content with 450 to the wheels ( for a week ) If I could keep it all in tact, by keeping the RPM's low, enough fuel, and safe of detonation, with a low amount of boost (under 10psi)

Ironically, getting max boost early in the RPM range might be worse for the motor than running it to redline since under those conditions (high cylinder pressure, low RPM) you're more likely to detonate. I don't think there's one magic bullet...you need a combination of moderate boost, good fuel, reasonable RPM and a good tune all together, especially on stock internals. 450 at the wheels? On stock - powdered rods and hypereutectic pistons and a cast crank - internals? Even with a good tune that might be pushing it if you want it to live for a while.

ProCharger GT · Apr 4, 2005

my_03GT · Apr 4, 2005

According to Kenne Bell's web site, high rpm kills engine's, not horsepower. Keep it out of the red with a good tune and it will be fine.

nickthegenius · Apr 4, 2005

Engine RPM seems to be the culprit. There are plenty of guys that have lost their bottom-ends on naturally aspirated cars shifting at 6500RPM. In a car with heads and cams,that is a fairly optimal shiftpoint, but the stock internals don't like to do it very long.

OinkAodeOink · Apr 4, 2005

Yea, the car is completely stock as far as the motor. Making 450 or more on the factory longblock won't be the problem, with the turbo setup.. I'm more concerned about what I can do to keep out of trouble, while still running a power adder.

Im new to the modular engines, so I was not sure just how strong, or weak they are with the factory goods in place.

BTW, the car is an 01 with a 4R70w trans, and will have a 62-1 or T70 single setup, with supporting modifications.

1low03gt · Apr 4, 2005

High rpm kills in the long.But then again i hang out with someone on this board that likes to hold rev's,and his 2V keeps going,keeps going,keeps going,keeps going,keeps going,keeps going,keeps going ....You got the picture.

Mike97gt · Apr 4, 2005

i agree with the guy that posted about keeping a good tune and resonable boost levels...

as long as your not over the red line you should be fine as far as rpm... detonation is the killer of boosted motors...

damien2003gt · Apr 4, 2005

1low03gt said:
High rpm kills in the long.But then again i hang out with someone on this board that likes to hold rev's,and his 2V keeps going,keeps going,keeps going,keeps going,keeps going,keeps going,keeps going ....You got the picture.

lol. Hey I'm not that bad! Yes I may crusie around now and then at 5200rpm down town but it aint that hard on the engine.lol I don't drive like that "all" the time. Mind you, I never shift under 4500 RPM..... Ah whatever WTF, its an OHV, it love to rev!

kj2833 · Apr 4, 2005

damien2003gt said:
WTF, its an OHV, it love to rev!

Im sure you meant OHC,

I forgive you though

sgarlic · Apr 5, 2005

Although KB says high rpm is what kills engines, you should ask the guy at modulardepot (can't remember his name) who went in to 9 psi boost in fifth gear at around 2k rpm and blew it up.

00s281sc368 · Apr 5, 2005

Stock internals are not designed to run above 6000rpm. That's where we stopped measuring the dyno, while the power was still climbing... But to go beyond 6000rpm, we need better springs/heads/valves than stock ones...
Also my previous saleen blower was making it's peak HP at 5000rpm, but think it was more damaging my engine though

1qko3 · Apr 5, 2005

sgarlic said:
Although KB says high rpm is what kills engines, you should ask the guy at modulardepot (can't remember his name) who went in to 9 psi boost in fifth gear at around 2k rpm and blew it up.

I don't think that is the same thing. If you start at a stop and go threw the gears shifting at 4,800 rpm that is alot easier on the motor than reving it to the rev limiter. But low rpm and alot of boost kills also if you are in a high gear.

HandofDoom_ · Apr 5, 2005

450 rwhp, goodbye stock block.

OinkAodeOink · Apr 5, 2005

HandofDoom_ said:
450 rwhp, goodbye stock block.

I was under the impression that the stock block is rather strong.. as in much stronger then the 5.0 blocks. The modular blocks look much more beefy.

Or are you refering to the stock longblock? (not actual block)

my_03GT · Apr 5, 2005

1qko3 said:
I don't think that is the same thing. If you start at a stop and go threw the gears shifting at 4,800 rpm that is alot easier on the motor than reving it to the rev limiter. But low rpm and alot of boost kills also if you are in a high gear.

I agree completely...what would you expect if you were in 5th gear and throw it to the floor with 2,000 rpm....can't be good...5th is overdrive,gas saver not for racing, when was the last time you hit 5th at the track???

1qko3 · Apr 5, 2005

OinkAodeOink said:
I was under the impression that the stock block is rather strong.. as in much stronger then the 5.0 blocks. The modular blocks look much more beefy.

Or are you refering to the stock longblock? (not actual block)

If HandofDoom knows what he is talking about he meant the internals not the block. And a stock 4.6 block will take a hell of a lot more hp than 450.

HandofDoom_ · Apr 5, 2005

1qko3 said:
If HandofDoom knows what he is talking about he meant the internals not the block. And a stock 4.6 block will take a hell of a lot more hp than 450.

I was talking about the shortblock, read as internals, not precisely the same thing but you get the idea.

Anyhoo, I have spoke to some people in the past and they said they've seen GT's break on the dyno @ much less than 350 rwhp.

1low03gt · Apr 5, 2005

damien2003gt said:
lol. Hey I'm not that bad! Yes I may crusie around now and then at 5200rpm down town but it aint that hard on the engine.lol I don't drive like that "all" the time. Mind you, I never shift under 4500 RPM..... Ah whatever WTF, its an OHV, it love to rev!

Hey,i didn't mention any names....

But then again i hang out with someone on this board

.... LOL!!!

Mike97gt · Apr 5, 2005

HandofDoom_ said:
450 rwhp, goodbye stock block.

thats only kinda true... a very very very good tune and the stock internals can survive more than that... but what are the chances of never getting detonation..

forged high quality parts give you a lot more survivabliity if the motor gets into preignition...

Weak point of 2 valve 4.6 motor.. RPM?

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