HOW MUCH BOOST CAN A 4.6 TAKE?

[bottlefed97]

My dad and I just finished putting the new motor in my 97 GT. It has a 98' NPI block, rods, crank, pistons, .030 shave P.I. heads, P.I. cam, P.I. intake, full exhaust, 75mm TB and plenum, and a CAI. It has roughly 60,000 miles. I sprayed my old stock 97 NPI motor with a 125 wet shot at least sixty times down the strip and it ran fine. I was thinking about getting a low boost vortech kit for the new motor, but people are telling me that it wouldn't hold up. Would six pounds of boost be too much??? Thanks!

Matt

 

[brightwhite98GT]

I would say on stock internals, no more then 8 pounds. I think that would be pushing it a little.

 

[justinschmidt1]

I think the stock internals would be fine at 11-12 psi with npi.

But your pi swapped and your compression is higher so your limited.

 

[nesqwick_05]

I would say on stock internals, no more then 8 pounds. I think that would be pushing it a little.

where do u get that idea, id like to meet this person who says that 8lbs is pushing the stock motor :idiot2:

 

[justinschmidt1]

Whats a safe amount of boost on stock internals? 11-12 you say?

 

[brightwhite98GT]

I would say on stock internals, no more then 8 pounds. I think that would be pushing it a little.

where do u get that idea, id like to meet this person who says that 8lbs is pushing the stock motor :idiot2:

Really? Quite a few people have told me. I dont know, maybe they were refering to my car specifically when they told me, because my car is high mileage (105xxx)

 

[justinschmidt1]

Hmm I think it would be more the condition of your motor than the mileage anyway...and from what ive heard boosting these motors with high mileage is not a problem.

Im gonna be boosting mine with over 105k

 

[voidfinger]

Since you got the pi swap... and at .030 shaved... you will not want to go over 8 and if so i wouldn't dream of taking over 10... and you better have a spot on tune. But I've driven a coupe with the pi swap and an 8 pound S trim and it was like a totally different car than a PI with 9:1 and 8 pounds. Felt kinda like 14 or so #'s to the back tires :dancing6:

 

[Dalamar]

Yes, as stated, 8# with your higher compression.
and watch out for any detonation. a few seconds on the stock rods and you'll be looking at a new shortblock.

 

[nesqwick_05]

in reality, no boost is safe boost. but if you wanna be able to get by id say 10-12 is safe on the stock pistons if u are tuned for it. if u run an fmu 8-10lbs. question isnt will it blow, its when, it will give one day or another, but u can improve longitivity by simple tuning.

the motors were not made for boost, u think it will live forever with it?? kinda like a midget, they where not born to play basketball, u think they will make it pro?

 

[voidfinger]

If you get forged internals you should be good... b/c these mod blocks are strait up beef dude. Kicks the 5.0 blocks in the nuts and walks away.

 

[97stanger]

boost is only a measure of restriction, it should be the rwhp/tq that you worry about. boost is just a number.

 

[GDawg]

I'm running a 9psi pulley on my stock '98... but I'm at 6,300 ft above sea level so I doubt that my actual boost is that high. I have yet to be able to find out for sure. I'm going to bump her up after a professional tune once I can find some fucking work around this deadbeat state.

 

[justinschmidt1]

boost is only a measure of restriction, it should be the rwhp/tq that you worry about. boost is just a number.

yea, boost is pressure..pounds square inch..you dont want too much pressure in your engine/

Ive heard that anything over 400hp is risky with a 4.6 450 rwhp+ is bad news.

But I wouldnte feel safe running 15psi on my stock engine, even if I only made 370 hp to the wheels.

 

[97stanger]

it all depends on the tune. thats the most important. every single car is different. I know guys that have blown their motor at 360rwhp and others still running 440rwhp and never had a problem. also depends on how bad you beat the car. My tuner told me to go no higher than 425rwhp.

 

[Jrgunn5150]

Yes, as stated, 8# with your higher compression.
and watch out for any detonation. a few seconds on the stock rods and you'll be looking at a new shortblock.

The Man beat me to it. You toher guy's remeber, he's at nearly 11:1.

 

[voidfinger]

boost is only a measure of restriction, it should be the rwhp/tq that you worry about. boost is just a number.

yea, boost is pressure..pounds square inch..you dont want too much pressure in your engine/

Ive heard that anything over 400hp is risky with a 4.6 450 rwhp+ is bad news.

But I wouldnte feel safe running 15psi on my stock engine, even if I only made 370 hp to the wheels.

370 rwhp is probably over 400 on the motor :thumb:

 

[lizzyfan]

Yes, as stated, 8# with your higher compression.
and watch out for any detonation. a few seconds on the stock rods and you'll be looking at a new shortblock.

I/C or meth is a must in this situation!

 

[bottlefed97]

So basically as long as I get a good tune, keep the boost and horsepower down below 350 wheel and around 8 psi, and don't beat on the car all the time, I should be ok?

 

[97stanger]

I would consider that extra safe, some of us are daredevils :afro: