[hada76]

Originally Posted by mechanic17

RE: exhaust. Have to disagree with 2ManyTAs. Log manifolds are a definite hindrance in the midrange+. I hate headers myself, and the RAREs with 2.5" outlets work well! Would love to have long-branches.

agree, logs are the worst, you will not get the full benefit of duals if you keep stock logs on

[2manyT/A'S]

Originally Posted by 3tas4me

I am looking to make my 1979 TATA run a little better. I just had a new dual exhaust system installed with 2 1/4 inch pipes all the way back through Dynomax turbo mufflers with an H pipe. The engine is otherwise stock with about 50k miles on it. Plugs, wires, cap and rotor are all reasonably new. The carb has been overhauled and the heads were also cleaned up. What have any of you done to get your W-72's to run harder? I am looking mostly for just changing the distributor timing curve and carb rejetting. I do not want to change cams or anything else, just want to maximize what the factory gave me.
The butt dyno tells me that the new dual exhaust did not seem to make much difference in performance, I am actually disappointed so far......

FIRST things FIRST........you didn't say what GEARS you are running.

3: 23 is stock 70 W72...have they been changed out,because that will really affect your BUTT DYNO readings....

[3tas4me]

The car is stock, so it has the 3.23 gears. I am not looking to set the world on fire here, just want to make it run the best it can for what it has, which is definetly not the case right now. The dual exhaust alone should have woke the car up to some extent. It is the mid-throttle where the car seems to not run good. Light throttle seems fine as well as heavy throttle.

[johnta1]

Is your car an automatic?
A higher stall converter would wake it up also.

[2manyT/A'S]

Originally Posted by johnta1

Is your car an automatic?
A higher stall converter would wake it up also.

The stick is "the given" in this equation....

ALL 79 W72's were sticks.

[rad400]

Rex RAIII heads were #12s not 670 heads 400 HO.

[2manyT/A'S]

I have several 78 W72 4 speed T/A's that are reasonably low mileage & basically STOCK,other than true dual exhaust (2 1/4") with set up carbs & HEI's and am VERY happy with MY butt dyno readings.....(78 W72 sticks came with 3:42's)

They DO pull pretty HARD & run GOOD but obviously the stock camshaft is holding them back.

You can probably bump your initial to 19.

Did you check for timing chain slop?

Is your stock EFE valve in place still? (and working?)

[3tas4me]

Ok, here is what I did. I pulled the stock 17059263 carb off and replaced it with a 17056263 that I have that is in good condition. I opened it up first and set the float level to 5/16 per HO Racing specs in the "Supertuning the Quadrajet" article. I checked the jets and metering rods and recorded what they are. The jets are 70 and the primary rods are 42K. When I removed the original carb, I noticed that the bolts were loose. Since the car acted like it was lean, this was a good indication that it probable was. I bolted the 17056263 carb on after cleaning and blowing it out. The car now runs like it should. Burned rubber as long as I wanted to in 1st gear when stomping on it after taking off. Pulled all the way to redline without a hint of pinging or any flat spots. I am now going to take the top off the 17059263 and record the jets and metering rods. I am also going to set the float level to 5/16, factory spec is 17/32 which is much lower! It is clear now that the car was having some carburetor issues. I will get the carburetor sorted out and then want to play with the timing advance.

[Zirconia]

Generally speaking I don't rev these cars past 4k. Most shifts were in the 3.5k range. Definitely had a few gears left on the martinique blue/black custom 78. Lots of things that sound good on paper (headers) don't necessarily work on these cars.
75 has stock 3.08 rear gears with close ratio t-10 and 2.43 first gear. Sounds terrible on paper, but this is a great combo on the street/road. Plenty of low end torque. Running only 2k at highway speeds.

[3tas4me]

Still looking for that HO Racing information if someone has it.

[Zirconia]

Originally Posted by 3tas4me

Still looking for that HO Racing information if someone has it.

Here is the data from the mods. Car was a 1977 Trans Am TA/6.6 Automatic, most luxury options (cruise, a/c, etc.). 3.23 rear gear. Data is for 0-50 mph in sec.

Stock baseline 7.0
H-O Power Kit (basically carb rejet) 6.6
H-O Accuracy Kit (dist recurve) 6.5
H-O High Lift Kit (1.65 rockers) 6.2
Tri Y Headers & CrossFire Muffler 5.4
Raise 1-2 shift 4.6k to 5.0k 5.2

To get an idea how your car should run (maybe a tick slower since this is a RAIII) please view my latest test drive video:
http://www.youtube.com/watch?v=8aBrM...hannel&list=UL

[rad400]

Zirconia that is a bad azz RAIII T/A.

[FrankieT/A]

In my opinion the only thing that's gonna wake up that car is another point in compression. Compression is directly proportional to acceleration. Maybe a set of 62's so as comp is not too high but still large valve. Don't forget those pistons are chamfered as well as a large chamber head.
I know you said you didn't want to change anything, but if want to make an omelette, you have to break some eggs! JMO

[3tas4me]

Car is running really good now that the carburetor is sorted out. If nothing else, it is at least performing as well as when it was new and I would bet slightly better with the dual exhaust. If I get a chance, maybe I will hook up my Gtech and run it.

[Zirconia]

Originally Posted by rad400

Zirconia that is a bad azz RAIII T/A.

Thank you. Not mine, a fellow TA enthusiast stopped by and showed it to me. He scared me. And pushed me back in the seat. Point is, properly runnning TA6.6 should be almost as fast.

[3tas4me]

I would actually disagree, stock for stock, a W72 should be about .7 -1 second slower in the quarter than a Ram Air III if you believe the period road tests.

[ta man]

More compression would help..have the heads been milled?

[3tas4me]

Originally Posted by ta man

More compression would help..have the heads been milled?

Engine is stock. I am trying to maximize what I have without pulling the engine apart or getting into expensive mods.

[Zirconia]

Originally Posted by 3tas4me

I would actually disagree, stock for stock, a W72 should be about .7 -1 second slower in the quarter than a Ram Air III if you believe the period road tests.

We are actually in agreement. As I mentioned previously, W72 is about "a tick" slower or 1 sec. slower.

[3tas4me]

Originally Posted by Zirconia

We are actually in agreement. As I mentioned previously, W72 is about "a tick" slower or 1 sec. slower.

Ok, got it. Too tired to think today....