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Bolt on power for a 305 TPI?

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Old Mar 14, 2021 | 12:48 AM
  #1  
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From: Michigan
Car: 1988 IROC-Z/G92
Engine: 5.0
Transmission: T-5
Axle/Gears: BW 3.45 Eaton Truetrac
Bolt on power for a 305 TPI?

I know I will probably get some flak for asking this, and it may have been inquired about in the past.
HOWEVER this is the present! The future!

I am finally getting my car together and into a place where I can enjoy it, but there is one thing I know I will be hungry for... A bit more power!
At this point I want to keep the engine in the car, as it has been out of commission for so long already.
I am just looking to maintain a semblance of fuel efficiency (Gas IS going up after all), and reaching around 300-350HP.

I have looked at a few intakes, such as the miniram and such, and I know those could potentially give me some decent boosts, but I'd like to have a comprehensive list if possible, while taking price into consideration.
Ideally Id like to take my current intake and have it ported out some (I certainly don't trust myself there) if anything.

I understand CXRacing has a turbo kit: HERE
Though I have no understanding of even the basics of turboing.

In fact I will be honest, I have very limited understanding of any of the true inner workings of the motor. THOUGH I am looking to learn, I do like to work with my hands.
I plan to learn as I go along here, and I am going to be tuning myself for the most part.

Anyways, let me know what I can do for a DECENT price to get a couple extra dogs (or horses) out of my current engine.
The only upgrade I have (that I am aware of) was from the PO, and that is a 58mm TB.

The engine has about 50,000 miles on it, I have a 9 bolt rear end with a torsen unit, the G92 package with 3.45 gears, and of course the T5, as well as a smattering of other suspension upgrades for the rear. I will list them if need be.

Looking forward to hearing some suggestions!

Last edited by Annihilate; Mar 14, 2021 at 12:52 AM.
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Old Mar 14, 2021 | 08:25 AM
  #2  
ironwill's Avatar
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Car: 1986 IROC Z
Engine: 5.0 TPI
Transmission: 700R4
Axle/Gears: 3.23 Posi
Re: Bolt on power for a 305 TPI?

There's not a lot you can do, bolt-on-wise; to extract 350 hp from a 305 will require significant and costly internal mods. One's budget and experience level have to be considered.

A cat-back exhaust will make the car sound better and maybe provide a few extra ponies. For a low-buck shot of temporary power, there's always nitrous, but I caution beginners to tread lightly; it can be the Killer Of Engines when installed improperly.

Keep in mind that anything that is done to substantially increase power output will have to be matched with modifications to the remainder of the drive train, and possibly an upgrade to the brakes and suspension.
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Old Mar 14, 2021 | 10:21 AM
  #3  
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From: South Ms
Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: Bolt on power for a 305 TPI?

You have a Third Gen with the factory setup everyone wanted. 5spd , TPI, 9 bolt rear.. Leave it alone it's a great fun car just the way it is and it's worth more factory.
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Old Mar 14, 2021 | 05:16 PM
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From: Moorpark, CA
Car: '91 GTA, '92 T/A Convertible
Engine: GTA: 350 w/Vortec heads, T/A: 305
Transmission: Pro-built 700R4
Axle/Gears: GTA: 3.27, T/A: 2.73
Re: Bolt on power for a 305 TPI?

There are two key things that jump out at me with your post.

1) You want more horsepower.....That will NEVER change. No matter how much HP you have, you'll want more. You want to do it on a "decent" price, but on a 305. Not compatible. That's like asking for a flaming hot ice cube. Not trying to chastise you, but have you done a basic search on this topic? It has been asked and answered a million times here on TGO. There are things you can do to give you a little bump in HP, I hate to say it but if you want HP at a decent price, then swap to a 350. It will be cheaper and the mods you do to the engine will respond better. Case in point; that 58mm TB is WAY overkill for a 305. If the plenum isn't port matched the TB might actually be hurting performance.

2) " I have no understanding of even the basics of turboing" and "I have very limited understanding of any of the true inner workings of the motor".....Before you even attempt to add something like a turbo or supercharger, you need to learn how everything works before you blow a piston or throw a rod before you even get the car out of the driveway.

I know this isn't the advice you want to hear, but you need to exercise some patience and learn more before you proceed. Start with the small bolt on upgrades and learn the basics of your car before you think about going all out on a 305. As mentioned before, just stick with the 305/T5 and have some fun. My '92 T/A has a 305 and its plenty of fun. Yours has the added benefit of the manual. Learn before you hurt the car or yourself.
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Old Mar 14, 2021 | 05:27 PM
  #5  
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From: Michigan
Car: 1988 IROC-Z/G92
Engine: 5.0
Transmission: T-5
Axle/Gears: BW 3.45 Eaton Truetrac
Re: Bolt on power for a 305 TPI?

I definitely plan to enjoy the car for the remainder of the year once it's put back together. Looking to my winter project already!

I do have a 350 Vortec stashed away from the late 90's. The guy I bought it from bored it .60 over, and that kind of concerned me. I was looking at the FIRST intake, which seems pretty interesting.

I appreciate the honesty, I've just recently rediscovered my love of working on cars, and I finally have some cash to back it up. I do tend to get ahead of myself.
I get a bit overwhelmed by the vast ocean of information out there that I tend to have a problem getting started when it comes to learning.

I'm not sure if the PO did any porting to the plenum, or if he was just throwing things at the car, I've been cleaning up some of his old issues, and learning as I go along. Even got my hands on the holy grail of shop manuals for my year.

While taking my rear end out I have been learning about suspension and upgrading all the essentials in that arena, ideally having SFC thrown on when I get the car back on it's wheels.

I've glanced over some topics in regards to this, but again, I don't absorb quite as much as I would like.

In the end I just gotta slow down... Would you have any areas of information that you would suggest I look into first? It would be appreciated!

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Old Mar 14, 2021 | 05:50 PM
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From: NYC / Jersey
Car: 1990 Trans Am GTA
Engine: Turbo 305 w/MS2
Transmission: 700R4
Re: Bolt on power for a 305 TPI?

Originally Posted by Annihilate
At this point I want to keep the engine in the car, as it has been out of commission for so long already. I am just looking to maintain a semblance of fuel efficiency (Gas IS going up after all), and reaching around 300-350HP...
I'll never understand why members feel they need to justify to other members why they want to build their 305 on this website. Build the damn thing and enjoy it, it's your car and that is why it is there, for you to enjoy...

Originally Posted by Annihilate
I have looked at a few intakes, such as the miniram and such
Don't waste your time. All you're doing is moving your powerband upward in the RPM band, and you'll be wringing it out just to justify any power increase, in turn killing your gas mileage necessity. Stick with the stock TPI.

Originally Posted by Annihilate
I understand CXRacing has a turbo kit: HERE
Now you're talking.

Originally Posted by Annihilate
... and I am going to be tuning myself for the most part
This is the main issue. A tune alone will get you more power than you realize, with the right tune.

Originally Posted by Annihilate
The only upgrade I have (that I am aware of) was from the PO, and that is a 58mm TB
Sell it, get a stock throttle body, and buy a decent cam kit with whatever money that remains matching your RPM band.

- Rob
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Old Mar 14, 2021 | 07:18 PM
  #7  
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From: Moorpark, CA
Car: '91 GTA, '92 T/A Convertible
Engine: GTA: 350 w/Vortec heads, T/A: 305
Transmission: Pro-built 700R4
Axle/Gears: GTA: 3.27, T/A: 2.73
Re: Bolt on power for a 305 TPI?

IMO, the very first thing you should do after you get it back together and running is to get some SFCs installed. You will be amazed at what a difference they will make, not just to the ride but to the car overall. They are important to getting your planned power to the ground. Start there, then circle back to everything else.
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Old Mar 14, 2021 | 07:36 PM
  #8  
Annihilate's Avatar
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From: Michigan
Car: 1988 IROC-Z/G92
Engine: 5.0
Transmission: T-5
Axle/Gears: BW 3.45 Eaton Truetrac
Re: Bolt on power for a 305 TPI?

I've got a set of the Spohn SFCs in standby. Just gotta get my rear end back on.
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