[BlackTA]

In a previous post I have been told installing an overdrive tranny will cost me upwards of $1500 plus probably some skills I dont yet have...so thats wout of the question. I want to do something to improve my mpg. My best guess is that I am getting 10 mpg now. (it is impossible to get an officail number as my speedometer reads off and I havent figured out by how much yet).
Searching around the forums I have heard that a q-jet carb would give me better mpg then my holley 750. How much mpg would I be gaining and how much HP would I loose also is this "qjet" carb the stock carb trans-ams origanally came with?
My second option would be to change my rear end right now I am running a 3.73. What is the stock rear end in a 79? I was thinking of switching to a 3.23. What would this cost and how involved is the process of switching rear ends? would switching rear ends give me a noticible increase in mpg (I do alot of my driving on the highway where in the slow lane with my current rear end i average 3250rpm). How bad will my acceleration suffer?

[BlackTA]

In a previous post I have been told installing an overdrive tranny will cost me upwards of $1500 plus probably some skills I dont yet have...so thats wout of the question. I want to do something to improve my mpg. My best guess is that I am getting 10 mpg now. (it is impossible to get an officail number as my speedometer reads off and I havent figured out by how much yet).
Searching around the forums I have heard that a q-jet carb would give me better mpg then my holley 750. How much mpg would I be gaining and how much HP would I loose also is this "qjet" carb the stock carb trans-ams origanally came with?
My second option would be to change my rear end right now I am running a 3.73. What is the stock rear end in a 79? I was thinking of switching to a 3.23. What would this cost and how involved is the process of switching rear ends? would switching rear ends give me a noticible increase in mpg (I do alot of my driving on the highway where in the slow lane with my current rear end i average 3250rpm). How bad will my acceleration suffer?

[henry203]

Switching from the holley to a good ole rochester will definantly gain you a little mpg, how much I do not know. The hp loss probably wont be too bad, cant give you an exact number.

Your biggest problem is that rear end. 3.73 is a pretty racy gear. Most firebirds came with either a 2.41 2.56 or 3.08 gears for mileage purposes. My ta gets about 12mpg city or about 14-15 highway with a 2.41. old 403/th350 tranny. dual exhaust/shift kit

at 60mph my RPM is about....1700-1800

My suggestion is to get either the 2.41 or 2.56 theres alot of high mph power and im assuming most of the time someone will try and mess with you will be on the highway since thats what you drive primarily.

If you want some more streetability the 3.08 is a healty medium. The 3.23 is a good gear as well but it wont save you as much gas as the others...which is what you want!

Other minor things you can do is make sure the engine is tuned up well, if you dont use AC or its not working take off the belt. Dual exhaust helps, you could use some wire and shut the secondaries...but your performance will suffer big time.

Your other option is to get a beater geo metro for $500, those get 30mpg use it for work and the other car for play!

[Trev]

I have done the 'beater' car thing in the past, and in my opinion, it does not pay. The only real reason to do it is if you don't want to drive your Pontiac in bad weather. If you add up all the costs of buying, maintaining, insuring, parking etc. It is an easy decision.

Having put overdrive transmissions in several of my Pontiacs, I strongly recommend that route to anyone trying to acheive the best compromise between driveability, milage, performance and comfort levels (interior noise). The satisfaction I get from being able to drive an excellent all round performance car makes it worth the money alone.

[carbking]

You probably need to do a little more homework here. As an example, one would think that if a previous owner installed a 3.73 rear end and the Holley that more than likely the cam was also changed. If this is true, then a stock Q-Jet will probably not work.

I would suggest determining exactly your engine specifications (a big cam MAY need the big rear end) first. Second determine your actual fuel economy. Determine odometer error by driving 10 miles between mile markers on an interstate, and then comparing to the reading on the odometer. Now determine how many miles you drive per year, the average price of fuel, and how much you would save by increasing fuel economy by 10 percent, 20 percent etc.

Once you have these figures it is easier to determine what can be done and what can be done economically to improve fuel economy.

Should you consider the "beater" idea, don't forget to factor in the additional cost of license, taxes, and insurance on the additional car.

Jon.

[BlackTA]

carbking... it has a "650 cam" but thats all I know about it the previous owner just said that.

maciej...When you say shut the secondaries you do you mean essentially turn my 4 barrel carb into a 2 barrel carb? If so I have noticed my fuel line splits into two before it enters the carb. I would assume one line goes to the front two barrels and the other to the back. Am I safe to assume this? If so what if I put a valve on that back line and could then turn on and off the back two barrels at will. Can someone tell me why this would never work so I can move onto my next hairbrained scheme.

[Philo]

Trev -

what type overdrive did you go with? I was looking at a "Gear Vendor's Overdrive" unit,
( http://www.gearvendors.com/custom.html ) but it costs a lot. A Tremec five speed is slightly less, but I am not sure which would be better. My TA has a 400/four speed and a 3.23 rear, but at 65 it is spinning at 2700 or so. When you are used to newer autos that run 1800 at 65, 2700 seems high as a kite. It is mostly wear and mileage I am concerned about, with mileage being second. I only drive it about 2000-3000/yr. With all of the torque it has, a six speed would be perfect, but I am on a budget, and don't know if a six speed can be adapted to the 400.

[Trev]

Philo,
I have used an aftermarket T56 kit in my 400 Trans Am. I sold the car, but still have the transmission and all parts to install. $1,500 takes the kit. It has less than 2000 miles on it.
My red 78 T/A has a 200-4R auto from Bowtie Overdrives. This set up was easy to install, and is a superb street transmission. My new project Trans Am is getting a TKO600 from Keisler Engineering. The car will have a lot more power than the T56 will handle.
As you can tell, I am completely sold on Pontiacs with overdrives. Most of these overdrives have a better first gear ratio than the original equipment transmissions. So you have the best of both worlds. Tire frying first gear combined with excellent highway cruising.
I did considder a Gear Vendors unit, but unless you already have a built T400 that you do not want to remove, then I think one of the above solutions is a better bet. Also I think the gear vendors only has a 0.78 overdrive ratio. The T56 has 0.62, the 200-4R has 0.67. Better value for the money in my opinion.

[BlackTA]

Just was looking at the ad that was hanging in the window of the TA when I got it it doesnt say 650 cam it says ".650 cam lift" Can anyone tell me what kind of rear end I can run with the cam and while we are at it would someone please tell me what having .650 cam lift means. I probably should also mention the engine is an oldmobile 350
-thanks