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TBI Throttle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.

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Old 10-23-2008, 08:53 PM   #1
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how much boost can a tbi350s bottom end handle?

i have a basicaly stock 350 tbi motor, its the truck motor so it does not have have a roller cam but other than that its the same motor you guys have. heres what im running, a whipple supercharger, bored throttle body, 80# injectors, methanol injection, and im tuning with a moates ostrich 2.0. the motor is a 2 bolt main, and i am peeking about 12 pounds of boost wide open at 5000 rpms, but for the most part, the truck doesnt see much more than 8 unless im either tuning or plain out drag racing it, which shouldnt be often once im done tuning.

so what do you guys think, its never crossed my mind before, but it is pretty obvious that this is alot of boost for a stock motor.

im building a 383 for it next summer with forged internals and it will be built for the blower, but for now, any one think its a big deal to run 12 pounds through this poor abused 200k mile motor for another 10 months till i build a new motor?

would it be wise to run the truck all the way down the drag strip pushing 12 pounds at a stock motor?
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Old 10-24-2008, 01:13 AM   #2
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Re: how much boost can a tbi350s bottom end handle?

its all in the tune..12 lbs is fine with a good tune. No detonation = no breaking ****.
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Old 10-24-2008, 02:38 PM   #3
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Re: how much boost can a tbi350s bottom end handle?

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Originally Posted by LoudmouthSS View Post
its all in the tune..12 lbs is fine with a good tune. No detonation = no breaking ****.
do you really think? its still a 2 bolt main bottom end. everything is pretty sound mechanically on this motor, it is very tough, and i have never ran it lean at 12 pounds of boost, the worse that happens is it will go to rich, maybe 10.5:1 worse case. but once again, its still a 2 bolt main bottom end. i read this reply no more than a minute after a read some one assuring me that my motor will go boom on another forum lol in my mind, i just couldnt see this motor going boom, i mean, it is just a really tough motor and has no real mechanical problems, the compression checks out at about 150-160, doesn't burn oil, its just a good motor, cant beet a good ole small block chevy....
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Old 10-24-2008, 03:15 PM   #4
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Re: how much boost can a tbi350s bottom end handle?

There is that one guy running around with a bone stock truck 350 (two bolt main) in his trans am running a big turbo setup..were talking like 700+ hp. He said he believes the key to his success is the fact that detonation is monitored extensively and he makes sure it never happens. Sure i mean parts do play a big part in the strength of a bottom end. But most failures stem from improper tuning and lean conditions. They say rich is safe and it's for the most part true. Plus 12 lbs isnt really THAT much, i mean for a stock bottem end i would say your still on the safe side. Everyone will give you different opinions though. I have 2 friends with mustangs..one has a 5.0 makeing over 400whp on the stock short block with 12psi unintercooled vortech. The other runs 15psi on a 3.8l mustang making over 400whp as well. It's all in the good tuning they both recieved.

But like i said, other people will say no no and that I'm wrong.

It's just like the arguement of nitrous..some say 100 is the limit on cast internals...holley says 20hp per cly so 150 is the limit. I run 125 right now and plan on going to 150 soon enough. Hell i run 8 degrees more timing then stock on 100 shot with stock plugs...even ran it on 87 once on accident. It's all in the tune...at least thats what i say haha.
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Old 10-24-2008, 07:05 PM   #5
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Re: how much boost can a tbi350s bottom end handle?

Quote:
Originally Posted by LoudmouthSS View Post
There is that one guy running around with a bone stock truck 350 (two bolt main) in his trans am running a big turbo setup..were talking like 700+ hp. He said he believes the key to his success is the fact that detonation is monitored extensively and he makes sure it never happens. Sure i mean parts do play a big part in the strength of a bottom end. But most failures stem from improper tuning and lean conditions. They say rich is safe and it's for the most part true. Plus 12 lbs isnt really THAT much, i mean for a stock bottem end i would say your still on the safe side. Everyone will give you different opinions though. I have 2 friends with mustangs..one has a 5.0 makeing over 400whp on the stock short block with 12psi unintercooled vortech. The other runs 15psi on a 3.8l mustang making over 400whp as well. It's all in the good tuning they both recieved.

But like i said, other people will say no no and that I'm wrong.

It's just like the arguement of nitrous..some say 100 is the limit on cast internals...holley says 20hp per cly so 150 is the limit. I run 125 right now and plan on going to 150 soon enough. Hell i run 8 degrees more timing then stock on 100 shot with stock plugs...even ran it on 87 once on accident. It's all in the tune...at least thats what i say haha.
on the fullsizechevy forum im getting torn up, they are telling me im an idiot and that my motors gonna go boom lol. this forum has a bit more technical knowledge so i think ill stay with the 12 psi and tune her good. i run 93 octane, methanol injection, 1 range colder plugs, and dont rry and squeeze as much timing as i can so detonation shouldnt be an issue. the one thing i am worried about tho is that i may be pushing the whipple too hard, it only peeked about 6 psi when i got it, but between the added rpms, methanol injection and the pulley(which was sonly supposed to make 8psi, it wasnt much smaller) im somehow making 12psi. it REALLY spiked up the last 2-3 pounds once it gets past 4700rpms, which is were it used to stop before i raised up the shift point. and the methanol does add a pound or 2, nobody ever believes me on this, but i swear, spraying methanol does add boost, i can see it with my own 2 eyes.

Last edited by chevy1500z71; 10-24-2008 at 07:09 PM.
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Old 10-24-2008, 07:05 PM
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