Coil Over Shocks (N/A)

[Crashnburn]

I have a 1981 Trans Am SE. I’m trying to improve the ride and handling. Apparently, coil over shocks would help with both. The rear suspension is leaf springs and I’m curious if the coil overs supplement or replace the leaf springs. I have a source for a conversion kit for all four corners.

Before coil overs, though, I plan to replace the chassis bushings. I can’t get a kit, so have to get them for each application separately. I’d rather not replace the leaf springs’ bushings if they go away when I convert to coil overs.

I’m asking here because POA has a giant brain trust and we all.come here from different walks of life. Thanks

 

[Bill]

I have a 1981 Trans Am SE. I’m trying to improve the ride and handling. Apparently, coil over shocks would help with both. The rear suspension is leaf springs and I’m curious if the coil overs supplement or replace the leaf springs. I have a source for a conversion kit for all four corners.

Are the present shock mounts sturdy enough to carry the weight of the vehicle? That would be my quesion.

 

[A Martin]

I have used them on my truck with good results .... just make sure you buy a good quality brand because the coil spring puts an extra load on the shock absorber .

I did it because the original suspension was a bit rough ... the coil-over shocks have a softer spring and it improved the ride which is mainly what I wanted .... it also raised the vehicle a bit (1/4" to 1/2") which was another plus.

Initially I flinched at the price (for a good quality set) .... but after 100k miles they were still good.


.

 

[mondtster]

Have a link to the conversion kit you’re looking at? That would likely provide information that would be helpful to give a more worthwhile suggestion.

 

[Crashnburn]

Sure. Here's the link.

https://www.classicindustries.com/product/1981/pontiac/firebird/parts/300108.html

Thanks

 

[Crashnburn]

A lot of life happened since my last post. I'm slowly doing a mild resto-mod on my Firebird.
In addition to the coil over shocks, I think I'll upgrade the upper and lower control arms.
These look compatible with the coil over shocks:

Speedtech Performance 20010: Upper Tubular Control Arms 1970-81 Chevy Camaro/Pontiac Firebird - JEGS

Get the Best Performance with Speedtech Performance Upper Tubular Control Arms 1970-81 Chevy Camaro/Pontiac Firebird 20010 parts at JEGS. Shop Now at the Guaranteed Lowest Price!

www.jegs.com

Speedtech Performance 20020: Lower Tubular Control Arms 1970-81 Chevy Camaro/Pontiac Firebird - JEGS

Lower Control Arms

www.jegs.com

Eventually, I'd like to install a frame stiffener kit.

Also, open up my shaker hood flapper door and install the mechanism to operate it, along with a kickdown switch.

Pontiac Trans Am Shaker

Pontiac Trans Am Shakers

pontiactransamshakers.homestead.com

My T/A is currently getting a new 4 speed OD 200R4 transmission, a new FlowMaster muffler, an new Cruise Control, and a new stereo, including a backup camera. I'm going to use synthetic transmission fluid for a little bit less viscosity and more power to the rear wheels. The muffler will also give a little more power, and more importantly, a better sound.

 

[455 Bravo Uniform]

If possible, confirm the longevity of aftermarket control arms. The originals are “soft” and prevent cracking. The tubulars are cool looking, lightweight, but may give up some durability with respect to road-life over tens of thousands of miles. Depends on how much you’ll use the car. Those were my concerns decades ago and the aftermarket may have proven they are durable.

 

[Crashnburn]

If possible, confirm the longevity of aftermarket control arms. The originals are “soft” and prevent cracking. The tubulars are cool looking, lightweight, but may give up some durability with respect to road-life over tens of thousands of miles. Depends on how much you’ll use the car. Those were my concerns decades ago and the aftermarket may have proven they are durable.

Thanks. I hadn't thought about that. However, I'm not putting a lot of miles on the car, and the whole idea of tubular control arms is so they'll be stiff and give you more precise steering.

 

[Crashnburn]

It's never as simple as it seems.

I talked to Tom (the mechanic at Street Dreamz today.) He has the new transmission almost done, except it doesn't fit the crossmember. It turns out I have a Pontiac TH-350 and it doesn't have the same length that the new 200-R4 is. I'll be calling Transmission Depot tomorrow to see if there's a crossmember they recommend so I can complete the job.

In the meantime, does anyone have a suggestion for a crossmember that will fit?

Also, he's recommending against upgrading my suspension. He says it is fine as is, no sagging, etc.

Also, I have the wrong muffler. The Firebird mufflers have one in pipes and two out pipes. This one only has one out pipe. He recommended I get headers and a dual exhaust, along with a second muffler. And open the exhaust up from 1-1/2 inch to 2 inches to let the engine breath, give a better sound, and a little more power. (I have a matching muffler on order already.) I have been toying with the idea of headers and dual exhausts, so I'm fine with the idea.

 

[Zeldman]

I have run hedders on most my V8 vehicles, even a Ford 300 ci straight 6 once, but with single exhaust pipe. 3 or 4 inch pipe to be exact, depending on cubic inches and the amount of modifications to the engine. To me the single pipe sounds better, plus it really embarrasses everyone to get out run by a pickup with single exhaust pipe. I have always used school bus mufflers for the best sound, but that won't fit under your T/A. 2 inch pipe is stock size from the factory. I would recommend a minimum of 2 1/4 to 2 1/2 inch pipe with hedders to open it up and let it breath, and better sound. (not louder) Too many exhaust shops try to sell 2 inch because it is easier to work with.

And yes, the 1981 model V8 cast iron exhaust manifolds are very restrictive.

And for goodness sakes don't let anyone sell you a Holley carburetor.

 

[DaleB]

In the meantime, does anyone have a suggestion for a crossmember that will fit?

Google “1981 trans am crossmember 200-r4” without the quotes. Looks like they’re not difficult to find….

 

[Crashnburn]

Google “1981 trans am crossmember 200-r4” without the quotes. Looks like they’re not difficult to find….

Thank you.

I did a little research and found a cross member for a second gen F-Body for a 200-R4 at Summit Racing. It also has a double hump for a dual exhaust setup.
I love it when things come together.

 

[Crashnburn]

I have run hedders on most my V8 vehicles, even a Ford 300 ci straight 6 once, but with single exhaust pipe. 3 or 4 inch pipe to be exact, depending on cubic inches and the amount of modifications to the engine. To me the single pipe sounds better, plus it really embarrasses everyone to get out run by a pickup with single exhaust pipe. I have always used school bus mufflers for the best sound, but that won't fit under your T/A. 2 inch pipe is stock size from the factory. I would recommend a minimum of 2 1/4 to 2 1/2 inch pipe with hedders to open it up and let it breath, and better sound. (not louder) Too many exhaust shops try to sell 2 inch because it is easier to work with.

And yes, the 1981 model V8 cast iron exhaust manifolds are very restrictive.

And for goodness sakes don't let anyone sell you a Holley carburetor.

Thanks. I thought Holley made good carbs. This car has a cross between a carburetor and fuel injection. It's CCC, Computer Controlled Combustion, I think. There's no choke plate, it's all controlled by the computer.

 

[Zeldman]

Thanks. I thought Holley made good carbs. This car has a cross between a carburetor and fuel injection. It's CCC, Computer Controlled Combustion, I think. There's no choke plate, it's all controlled by the computer.

Could it be a Throttle Body Injection unit? My knowledge is mostly carburetors, yes I am that old...

 

[Crashnburn]

Could it be a Throttle Body Injection unit? My knowledge is mostly carburetors, yes I am that old...

No. I think the on-board computer actively manages the fuel flowing through the carburetor for maximum efficiency. The Gen 3s had true EFI.

 

[Plano Pilot]

Back when I was into old cars, I liked the Holley carbs. They were easy to rebuild and change the jets. I was not very successful with the Rodchesters.

 

[mondtster]

Thanks. I thought Holley made good carbs.

They're fine. There's a reason they have been one of the standards for performance applications for years, and why there have been numerous clones made of them.

No. I think the on-board computer actively manages the fuel flowing through the carburetor for maximum efficiency. The Gen 3s had true EFI.

GM had computer controlled carburetor systems on various cars in the 1980s. I haven't had one or worked on one since the early 2000s, so I don't know how gracefully they've aged, but I didn't think they ran too bad back then. The electronic carburetors I worked on were fairly complex however, so there was plenty of opportunity for people to get them messed up.

 

[Crashnburn]

I did a lot of searching for headers for a 1981 Trans Am with a 4.9L/301 engine, and nothing fits. Still, how much absolute power increase can headers give a relatively low displacement engine. I know it's a compromise, but I'm thinking of keeping the exhaust manifold until if/when) I do an engine swap and then go to headers. In the meantime, go with a dual exhaust setup. The engine will still breathe a little easier, make a little more power, sound better, and the dual exhaust will be in place in case I do an engine swap.

Edit:
I pulled my plans back even further. I found a 3 chamber, series 50 Flowmaster muffler with one in and two outs that should fit where my current muffler is. I'll try to sell the incompatible muffler online.

I'll wait to do dual exhausts and headers if I do an engine swap.

Edit. 11/09/20024

Turns out the dual exhaust muffler still wasn't the right one. Thankfully, the muffler shop had a Flow Master Super Series 80 dual exhaust muffler that works. The car now sounds wonderful. Tammy would have loved the sound.

The mechanic drove the car to the muffler shop for me and told me it seemed a little doggy. I wasn't surprised because the 4.9L isn't nearly the engine the 6.6L was. Still, when I drove it, it seemed a little perkier than before.

The OD automatic shift detent plate and neutral safety switch both need to be installed, and he'll install the mechanism that will activate the flapper door on my shaker hood. That will give me a few more HP as well as a unique sound to the car.

 

[Crashnburn]

I found a pretty good website: Firebird Nation and made some inquiries about headers. Apparently, the headers for the standard block size will fit the short deck engine, but the exhaust manifolds are a PITA to remove. So, it looks like my decision not to do headers and dual exhaust was the right one.