meh2004

just got a third gen and excited to start working on it.

want to increase HP, i know it wont be much because its a 305 but would like to keep engine as is (somewhat) and just get some performance part.

any ideas?

yaj15

iTrader: (3)

Make sure the car is in good running order first. The first job is to make sure that the car is mechanically in good working order before you start modifications. Otherwise you will start throwing in good money after bad.

The suspension bushings and shocks should also be looked at. The fuel system, brakes, engine, transmission, rear end, ignition system, etc., and all the associated fluids for each system should be fresh. That way you will get the best performance from your mods because you will have a solid foundation.

How many miles are on your car? How well was it taken care of over the years? Those are also considerations that you have to deal with along with adding performance.

The 1985 LB9’s were the most powerful 305’s that GM paired with the 700r4. There are great gains that can be made from mods but you have to decide what your car will be used for first before you make modifications. This way you will get the ‘best bang for your buck’ in terms of the money you spend and how you will use the car. You also won’t end up with a car that you don’t like because you modified things in a way that are not in line with how you use the car.

You need to decide if you want a fast street car or something that’s sees some racing environments as well. Also Z28’s and IROC’s specialty is in the handling department. These are still the best handling stock Camaros that were ever made. These cars were pulling 0.92g’s on the skid pad 25 years ago without all the magnetic shocks and more modern suspension components that many of today’s’ top performance cars have.

If you race your car are you going to be drag racing, auto cross, road racing, etc.? Each one of those racing environments lends itself to some mods that may be better suited to one specific type of environment than another. For example the firm suspension settings you would use in road racing (to help out in the handling department) wouldn’t necessarily be condusive to the drag strip. There the suspensions job is to transfer as much weight and force (as efficiently as possible) to rear wheels.

Most of us on here want a fast street car. After making sure your car is mechanically up to task there are some easy mods that will really add power.

Also keep in mind that since you are going to keep the TPI system, understand that TPI’s job is to produce a good amount of power and torque in the low-mid rpm range. TPI is never going to be a high revving 7,000rpm system because that’s not what it was designed for. Even with saying that, however, don’t believe the folks that say TPI is bad news. Once you understand how it works and make a good selection of a combination of parts that work well together you will be able to surprise a lot of people with a TPI set up.

With that being said stock TPI systems were designed to perform best in the idle-4500rpm range. With modifications this can be extended to around 5500rpm-6000rpm. It’s important to keep that in mind so you select components that will perform well in the operational rpm range that you drive in most of the time and that complements the power train in your car. So don’t get a camshaft and cylinder heads that start pulling strong past 5,000rpm and keep it going until 7000rpm because that’s out of TPI’s power band. Also you don’t need to go out and buy a Ford 9’’ rear end for the power level that you are at either.

Get some aftermarket air filters. It’s a cheap mod that will give you some horsepower gains later on down the line but there is a small benefit with the stock set up.


Consider installing a ram air intake system and cutting out the bottom of the air lid where the air filters sit. Camaro TPI cars really get a benefit if duct work is installed behind the fog lights and is connected to the bottom of the TPI air box lid. Most of the air used to make air flow across the radiatior for cooling comes from the front air dam – black strip of plastic underneath the front bumper. I installed Hawks Thirdgen ram air boxes on my car and gutted the air box. It does give a noticeable gain in performance. Later on down the line if you decide to install a larger throttle body, aftermarket intake runners & base, you will really see a good increase in performance.

Also make sure you have fresh spark plugs, distributor, wires, and all the other components should be in good working order with respect to the ignition system.

Exhaust is also a good spot where TPI cars pick up a good amount of power. Get some headers, aftermarket cat (if needed) and cat back exhaust system. Also you have the single 3’’ TPI cat exhaust. I got my headers from Hooker and I am very satisfied with them and they really woke my car up. I’ve got them ceramic coated to. That lets the headers keep the heat contained inside the tubes more which keeps the temps down lower under the hood and makes them more efficient. I’ve got 1 5/8’’ primary tubes that collect in to hookers’ y-pipe with a 3’’inch outlet. 1 5/8’’ primaries work best if low and midrange torque and power production if that’s what you are after. Modified cars may be better off with 1 ¾’’ primary tube to take advantage of the additional air and extended rpm ranges that those engines are capable of. As far as the cat back is concerned pick one that has the sound that you like. There are many threads on this website as to which is the best one but, pick a cat back exhaust system that sounds good to you and you should be happy. I run a 3’’ Flowmaster cat back on my car.

Next we should move on to the drive train. Consider getting your transmission rebuilt and installing a higher stall torque converter. This will give you firmer shifts, higher quality transmission components, and better durability for more power later on down the line. The converter will also help out with acceleration by allowing the engine to easily get in and stay within the power and torque band. Stock stall is very low around 1600rpm – 1700rpm. Most stock style long-tube-runner TPI systems like stalls between 2200rpm-2500rpm. I’ve got a Bowtie Overdrives level 3 700r4 and 2400rpm stall converter in my car and I’m very satisfied with it.

Last let’s get to the rear end. You have the 10 bolt rear end. It’s not as strong as other rear ends that are out there but for basic mods this rear end will be more than enough to handle what you are asking of it. GM made 10bolt rears in massive quantities so as long as your rear ends’ housing is in good shape you can purchase everything else that you need for not too much money. Make sure you have positraction (RPO option code G80) and figure out what gears that you have. Not all of the LB9/700r4 cars came from the factory with positraction. Even if it did, after 27 years of service you shouldn’t be surprised if it’s worn. Most TPI cars perform very well with 3.42 gears. If you do end up deciding to swap gears make sure that you get the proper speedometer gears so that your speedometer will read correctly.

meh2004

thanks,
currently deployed but will behome soon
the car has 119k reading but engine was rebuilt and it has 10k i have not looked at it but the car was a steal.
And yes i will check the car that is mechanically good before adding anything to it.
i would like a fast street car something that i can use at a regular basis to show while driving around.
thanks again will take on your advice.

yaj15

iTrader: (3)

Thank you for your service! We have quite a few members that have served in the military or have family members that have (like I do). Really we can't say enough thanks for what you folks do to keep us safe!

Thats great that the engine has a fresh rebuilt on it. As long as it was done properly that will get rid of some of the issues that you deal with when you start working on an older car. Hopefully they rebuilt it to stock specs. The 1985 LB9's have usually performed very well for what they were straight from the factory. The 9.5:1 compression ratio has a lot to do with that. It also used a camshaft that was very close to the specs of the L69, which itself was based off of the cam that GM used in the 350 Corvette engines.

You won't have a problem getting that LB9 to perform the way you want to and you won't have to spend a ton of money to do it. Keep us updated on how things are going. Always good to hear that another thirdgen is going to be kept on the road and not rotting away somewhere!

ASE doc

Using stock heads with porting work done, a cam, headers and better flowing exhaust, the 305 was seeing an increase of 80HP back when they were new. The TPI will support 350HP as is. The key is to get the engine to move the air. Some improvement can be had by improving valve action with a better cam but you quickly come up against the poor flow of the stock heads. Porting, mostly a clean up of the rough casting and some work in the bowl areas and smoothing out the short turn radius, will solve this, along with minor machine work to allow for more lift, up to about 320HP. With a head swap and even larger cam, and hi flow TPI pieces, you can move on past 350HP, though you will begin to lose some drivability as you push past 1HP per cubic inch, on a naturally aspirated engine.

meh2004

thanks for the advice that im getting. Im back home now and excited to start working on the iroc. like i said before the engine was a rebild and from the looks of it it was build right. i took the car for a quick drive and i notice that the transmission jumps when changing from park to drive (automatic) it also does when gears changes from 1st to 2nd. i think the gears might just be slipping. any suggestions? im going to start changing the basics like engine oil wiring sparkpulgs (if needed) to start fresh. is there one thing i should look in to first before anything else?

Uppersub

I'm intersected to hear how this turned out. I have an 85 Z28 LB9 and want to do something similar to this. I read a thread about changing rocker arm ratio to increase lift instead of adding a cam.