[BlackTA]

Hi all,
I am a senior in high school and just got a 1979 Trans Am, black with a gold bird. Before this I had a number of junk cars, an 84 dodge pickup, an 88 dodge shadow, and a 92 saturn SC. I have no experience with a muscle cars but I am trying to pick things up as fast as I can, but I've got some questions I hoped you could help me with...

The car has an Oldmobile 350 with headers, a holley 4 barrel 650 cfm carb, and a 650 cam(anyone got an estimate on the HP i am putting out). I am getting maybe 10mpg if that. I work about 25 miles from home and in the round trip I use a quarter tank of gas. Its got a 3 speed automatic tranny. I would really like to swap it out for a 4 speed stick but I assume that would be very difficult so I was thinking of swapping it to a 4 speed auto. Will this help a little with my gas milage I spend most of my work commute on the highway and as I am sure you all know the 3 speed really has no highway gear. Would a 4 speed give me any better gas milage or am I just dreaming and need to get used to spending $100 a week on gas?

The car has a 3.73 rear end but noone ever changed the gear for the speedometer so it reads off im not sure by how much. Where is this gear, how much does it cost and how much of a pain would it be to fix?


The car is running Glasspacks right now. I like the sound they put out but my parents have other ideas...the neighbors probably are not overjoyed either so I am thinking of changing the exaust. I dont want to go stock, and I still want an aggressive muscle car sound just with alot less volume then the glasspacks. Id like to be able to have a conversation on the highway. What would you recommend.

Whats a good place to get parts for the car I am looking for a bunch of misc interior pieces mostly.

As I seem to be writing a book here I guess I will stop with the 20 questions untill another time...thanks for the help

[BlackTA]

Hi all,
I am a senior in high school and just got a 1979 Trans Am, black with a gold bird. Before this I had a number of junk cars, an 84 dodge pickup, an 88 dodge shadow, and a 92 saturn SC. I have no experience with a muscle cars but I am trying to pick things up as fast as I can, but I've got some questions I hoped you could help me with...

The car has an Oldmobile 350 with headers, a holley 4 barrel 650 cfm carb, and a 650 cam(anyone got an estimate on the HP i am putting out). I am getting maybe 10mpg if that. I work about 25 miles from home and in the round trip I use a quarter tank of gas. Its got a 3 speed automatic tranny. I would really like to swap it out for a 4 speed stick but I assume that would be very difficult so I was thinking of swapping it to a 4 speed auto. Will this help a little with my gas milage I spend most of my work commute on the highway and as I am sure you all know the 3 speed really has no highway gear. Would a 4 speed give me any better gas milage or am I just dreaming and need to get used to spending $100 a week on gas?

The car has a 3.73 rear end but noone ever changed the gear for the speedometer so it reads off im not sure by how much. Where is this gear, how much does it cost and how much of a pain would it be to fix?


The car is running Glasspacks right now. I like the sound they put out but my parents have other ideas...the neighbors probably are not overjoyed either so I am thinking of changing the exaust. I dont want to go stock, and I still want an aggressive muscle car sound just with alot less volume then the glasspacks. Id like to be able to have a conversation on the highway. What would you recommend.

Whats a good place to get parts for the car I am looking for a bunch of misc interior pieces mostly.

As I seem to be writing a book here I guess I will stop with the 20 questions untill another time...thanks for the help

[78 GHOST]

Hi Jeff, welcome to the Pontiac addiction therapy group

Some general ramblings:

First off, a tranny swap is easily $1500-2500 depending upon the unit chosen, your skills, and a ton of other variables too numerous to list.

You would have to obtain an overdriven transmission (either Auto or Manual) to achieve any mileage gain whatsoever. At most you're talking about maybe 20-30% improvement. This is a huge improvement, but incredibly costly.

The Olds is a decent motor. Headers are good, although improperly sized (too large primary tubes) can hurt bottom end drivability.

I'm not familiar with the specifics of the Olds family of motors.. but the Holley would not be my primary carburator of choice for a daily-driver application.

Specific recommendations:

-Keep Mom, Dad, and the neighbors happy.. spend $100-150 on some quieter mufflers.

-Optimize what you have.. tune, tune, tune.
You will never realize the full potential of your combination unless you dial everything in as accurately as possible.

-Optimizing includes ensuring the Distributor is working properly, including Vacuum Advance correctly attached to a ported vacuum source. The mechanical advance should operate smoothly and at some point, you should have it properly "curved" to ensure the spark advance is being added at the right time.

-Change all the vacuum hoses for new ones.

-Install a Quadrajet carburator which has been prepared for YOUR engine, trans, rear end ratio. Spend some dollars and get the right person to do the work. CliffR provides excellent value.

-Unfortunately, a "650" cam means absolutely nothing to me. I can tell you this, it is very common for owners to install too much cam into their engines, and then wonder why it's good manners just went in the crapper. Lumpy cams sounds great, impress the parking lot crowd, and deliver horrendous performance and economy when mated improperly to a vehicle not suited for it's ideal RPM range. 6500 RPMs does you absolutely zero good. Nice on paper, sucks in the real world.

These are just a few of the things to consider as you strive to restore economically realistic performance to your ride.

To compare, I have a '78 Trans Am with a Pontiac 400. The engine is essentially stock including the poorly designed intake manifold. It breathes through the equally poorly designed cast exhaust manifolds. The carburator is a stock Quadrajet which has been carefully tuned, including proper choke operation. At the time of peak mileage measurement, the filtration was with a K&N, also using synthetic oil, and had been recently tuned and decarbonized.

The trans is a TH-350 driving a 2.56:1 rear end. The cam has lobes smaller than the sweater kittens on Calista Flockhart. In other words, on paper this car should be a real bow-wow. However, it's been carefully tuned to become very reliable and will surprise you with it's strong accelleration.. it will smoke 'em.

Mileage: Documented 22.5 MPG at 65MPH w/o AC on. Your driving habits are probably the single biggest contribution/detractor from fuel economy.

[Young One79TA]

I'd also think about losing those rear gears if you drive it a lot. I wouldn't go any lower than a 3:42 gear for daily use. If I were you I would swap those gears for a higher 3:23 or 3:42 gear ratio.

[henry203]

Holleys are known for adding HP but killing you on gas. Get a good reliable rochester carb nicely tuned and fixed up for the specs of your engine. This will really help. As for the 3.73 gear that is a big factory. If you swapped to maybe a 3.23 you would see 2-3mpg more. At the momeny my 79Ta 403/350 (got it as a senior of high school too!!) gets about 12mpg CITY with a 2.41 gear.

The four speed wouldnt really give you a TON of difference, only overdrive would. Think of it this way. If you spend $1,500 to install an overdrive transmission how long will it take you to make installing the new tranny worth it? You may save $5 a week on gas but....your out $1,500!!!!

[mothermuxer]

Get rid of the glasspacks. I had them on an old 79 T/A, and it did sound cool, but it was a squad car magnet. Check out the exhaust systems from Pypes.

Interior pieces can be had thru Performance Years, or Classic Industries. You're better off visiting your local Pick-a-part, or sometimes Ebay, as the catalog items are a bit pricey. Either way, you'll probably have to paint them (the catalog parts are usually molded black).

Do yourself a favor and decode your VIN number, to see what the car has/had. Also, if you're interested, you can get a copy of the original build sheet from phs-online.com... that is if your car doesn't have the original sheet hidden behind the rear seats. Always some good info there.

The PY boards are a GREAT place to find info... just use the "find" function, and chances are it's been discussed here a bazillion times.

[BlackTA]

thanks for the quick replys...In my local want ads this is for sale..."1986 firebird trans w/ overdrive & rear end posi" any chance that would bolt right up to my 79? It is only $150.

[henry203]

As far as I know the 82+ model F bodies had a smaller rear end, 8.2". The 70"s cars had 8.5 The trannys in the those cars are also computer controled...to a degree. So im not positive it will work. The cross members are probably different and the bolt holes are more than likly not the same either.

A have heard a 200r4 from a grand national will work directly. Same cross member, same drive shaft, same mounting pattern. I would read up on that a little more.

[ChrisTransAm78]

Changing out the rear gears will give the most improvement right away... alittle pricey but gas mileage seems to be your deal. Tranny swap? I did one from an auto to manual 5 spd. About $2600. Yours will be a little less since you have some of the parts already. Forte's Parts sells everything you need to do it. Tell em Chris sent you if you go that route. They have pics of my install on their site. I have them on mine as well. Fairly detailed enough to see what you'll be getting into. Glasspacks? Only on a broken down beater redneck truck are they supposed to be found. (Sorry had to inject some Star Wars humor there!) Neways good luck on the project and welcome! BTW feel free to send me questions over email and I'll try to shoot you to the right places as I am almost complete with a 78 TA resto and I've done alot of the places finding for you.... uhg!