[chief455]

76 T/A
3.5" collectors to 3" reducers
I want to run 3" front pipes to 3" inlet mufflers.
Then either 2.5" outlet or 3" outlet to a 2.5" reducer.
I want the 2.5 tailpipes for more room and mostly to have quarter exit with splitter tips.

I'd love to run 3" all the way out, but that would mean rear exit and I don't care for that look.
Can someone supply the mixed sizes in a system (PYPES) and any great loss going to 2.5 for tail pipes?

[Silverbird]

dont know why you can't have a rear exit ..look at these with 3"

3" tailpipe thread

custom exit pics

Or

[Steve C.]

Curious, how many cubic inches & rpm involved with the combo and what power level are we dealing with ? ET ?
H-pipe or X-crossover ?

[chief455]

Originally Posted by Silverbird

dont know why you can't have a rear exit ..look at these with 3"

3" tailpipe thread

custom exit pics

Or

Those are all nice.
I want splitters.
I want a bolt on kit -
Nobody answered in your thread either - any loss going to a smaller tailpipe?

[chief455]

Originally Posted by Steve C.

Curious, how many cubic inches & rpm involved with the combo and what power level are we dealing with ? ET ?

good questions:

467ci
6500rpm
600-625hp
10.6 et (guesstimate for now)
I'd do either H or X

[440GP69]

X pipe for sure! 2.5 outlets won't hurt performance the muffler is the restriction not the pipe so run your splitters and have fun!, PS that TA is now in my top 5 all time dream cars beutiful job!!!!

[chief455]

Originally Posted by 440GP69

X pipe for sure! 2.5 outlets won't hurt performance the muffler is the restriction not the pipe so run your splitters and have fun!, PS that TA is now in my top 5 all time dream cars beutiful job!!!!

thanks! I got a nice roller to start with!
I'm going to start an assembly thread this weekend.
Just putting the top end on the shortblock then the install and first runs.

I'll see what happens - when it runs - how much $ I have - lucky I'm this far.
But I have not compromised my goal while buying parts!

[440GP69]

so how did your heads turn out? 310 KRE D's right?

[chief455]

Originally Posted by 440GP69

so how did your heads turn out? 310 KRE D's right?

Waiting for them to arrive. I'll post up pics.
Dave was sure I'll be pleased and he is clear on my goal.
He did the 6X heads/cam choice that were on my car running 10.40's with more compression, and he estimated the KRE's chamber and flow would pick up ~40hp/tq even with the lower compression. The cam is almost identical but with a wider LSA for street manners.
The short block is actualy better - stroked and 6.8" aluminum rods vs. 6.625" Eagle H beams. All else the same.
I just want the car to stay in the 10's in race trim but on pump gas. I'll be at the track later and find out

But the intent of this thread was to seek actual users of 3" exhaust for 2nd gen F-bodies with smaller tail pipes - or dyno testers with information about power effected.

[Steve C.]

If it helps here is what I currently have on my '70 Trans Am with the current 505cid combo, it appears to support my 600+ horsepower ok, the car has run 10.63 at 127.05 mph at about a 3750 lb race weight. It is primarly a street car and seldom sees the track, and the combo makes peak power at 6000 rpm.

2-inch primary headers with 3.5-inch collectors.
From the collectors I use a universial X-pipe kit from Dr.Gas, the tubing size is 3.5-inch into the x-pipe and 3.0-inch out, this takes up the space from the headers to the mufflers. My mufflers are Dynomax Ultraflow Welded with a 14-inch shell/ offset-3" in & 3" out. These mufflers have a 1100 SCFM flow rating and will support this power level. But they are a straight thru design and unlike a turbo style muffler that are not a straight thru design they are not as quiet, but as a comparision the Dynomax Super Turbos flow less at 552 SCFM and according to the manufacture will support 504 hp with a dual system. My tail pipes are 3-inch from Torque Tech, they exit similar to the factory location on my year. The entire system is modified and tucked up for the best possible ground clerance.

http://www.popularhotrodding.com/fea..._am/index.html

[Steve C.]

Pontiac Dude has an interesting chart for recommended exhaust sizes:

http://www.angelfire.com/fl4/pontiac...xh.sizing.html

[Larry Navarro]

complete 3" exh w/flowmasters

[chief455]

Steve C.
thanks for the detail and links!
I have always loved your car and we share similar thoughts on what a street car should be able to do

My first questin - where did you get your hood? Is it one piece or seperate scoop?
Any pics you could share of that set up?

Personally, I do not like the straight rearward exit of your tail pipes - mine is a 76, I feel it will look right with splitters.
I had a 600hp 474ci '70 Firebird a few years back with 3" out much like yours - but no crossover and the poor flowing Dynomax mufflers. That is an eye opener!
I'll likely use a PYPES 3" X-pipe system and adapt their 2.5" quarter exit tails and splitters. Just because "as formed" the tails should place the splitters in the right location for looks.
Will smaller tails slow my car down compared to 3"?
I'll never know, so I'll tune what I like to go as fast as it can
I will be running my car as is in race trim before adding the exhaust, power steering, different hood and perhaps a larger fuel cell or stock tank with a sump. I like my trunk space, and a factory look back there. It will be intereting to see how much slower it gets as it becomes more fun to drive on the street!

Unless someone can form the 3" tails to look right with splitters exiting like a 76 did.

[chief455]

Originally Posted by Larry Navarro

complete 3" exh w/flowmasters

Sweet! Looks much like Steve C.'s car....

[Steve C.]

Chief455- Thanks for the kind words I appreciate that.
My 'glass hood was made by Fiberglass Trends, part number 2235 which is listed as '70-'76 Firebird T/A Hood Shaker bolt on. It came with the hole for a factory shaker scoop but in it's place I had a actual Trans Am scoop grafted onto the hood. I got it about 9 years ago and at that time Larry Navarro did not have his WFO kit in production to mount the shaker scoops for use with taller aftermarket manifolds, today you can use his kit if you want to retain a functional shaker scoop. Or if you need a hood scoop that mimics a factory style only slightly larger in size for extra room under hood you can purchase a "Dude Scoop" from Pontiac Dude (Ken Keefer) and mount it to the hood.
Example here: http://www.angelfire.com/fl4/pontiac...8/Scoops2.html

[chief455]

Steve C. - thanks for the info!
I see your Victor/Dominator and that's what I have as well.
My car came with a 4" pin on cowl hood and I don't like either - pin on or cowl
It's light, but I want a hinged shaker, so I'll follow your leads.

[Steve C.]

I typicaly run a HP950 carb, inorder to get it fit under my hood with a Victor intake installed, and with a small air cleaner in place, I had to mill 0.650" off the Victors intake flange. With the Victor/Dominator carb set-up in place there is no way I can use an air cleaner. With a larger "Dude Scoop" it might work.

[chief455]

Originally Posted by Steve C.

I typicaly run a HP950 carb, inorder to get it fit under my hood with a Victor intake installed, and with a small air cleaner in place, I had to mill 0.650" off the Victors intake flange. With the Victor/Dominator carb set-up in place there is no way I can use an air cleaner. With a larger "Dude Scoop" it might work.

You mean a 4150 Victor intake, stock, and HP 950 vs 0.650 milled 4500 Victor/Dominator carb? Or do you adapt the 4150 carb to the 4500 intake?
My car ran a stock height Victor intake/1" spacer/Dominator.
I'll remove the spacer - but no lower.
Too much power loss. Hopefully I'll get a shaker looking scoop to fit.
Looking at the pic of your scoop opening, I'm simply going to put air cleaner element across that, rather than atop the carb opening. With the base sealed to the scoop - should filter fine for fair weather driving. And leave room for air around the carb venturis.
May not flow air like a race scoop, but I'll remove the element at the track.
Thoughts?

[David Holmberg]

Chief, on my 77TA, I had 3" with an X to the same mufflers Steve used, and 3" torque tech tail pipes. Very quiet and runs 10.90's on motor and 9.90's on the bottle.

I've recently went to Pypes 3.5 head pipes, X pipe and Pypes mufflers. I re-used my old 3" tail pipes, so I'll be in the same boat as you, but larger. As of now I've not been able to do any testing, but the SOTP on the street is very promising.

The angle of my tailpipes (along with Steve's and Larry's) can be cut and the splitters added. If you look just behind the rear tires you can see the tip of the tail pipe.

474, small roller, victor 4150 Holley, 87cc E's and Pump gas.

[Larry Navarro]

The tailpipes can be easily shortened and "sectioned" so that they fit up behind the 1/4 panel. I started out with a pair of Flowmaster tailpipes that stuck straight out the back.
After cutting and fitting, the splitters fit and look factory.