We will start installing exhaust on our 72 in a couple of weeks. We're replacing the entire exhaust system, and want to run headers with some Flowmasters. I'm basically looking to install a stock system as far as pipe size, etc.

If I get a complete exhaust system from one of the vendor catalogs, will it bolt straight to a set of headers? If not, how much cutting, welding etc. has to be done? I'm running a 350 small block with the TH400 automatic.

(Its easier and cheaper for me to order an entire system than to take it to a muffler shop, the body is still off the frame and I'm trying to get as much done as possible with the body off).

Any suggestions for combinations or guidance for what I have to do would be appreciated.

 

I have the same setup....72, small block, 400 tranny. I'd suggest going to 2 1/2 inch pipes right away. Your exhaust will flow freer and if you increase hp later you'll need it. Don't worry about low end torque loss, your headers will take care of that.

Regardless of which brand of exhaust you buy, you'll probably find that you need special cut and fit pipes for the header attach end and through the frame crossmember.

On my system (with Flowtech headers) I had to create special reducers at the header flanges to route around the 400 tranny.

Here's a muffler flow chart I clipped from an earlier thread.

OEM..................................... ........................................ ...225
Gibson SuperFlow 788200.................................. ............311
TTS Bullet Cat Converter............................... ..................324
Flowmaster 40 series 42540................................... .......352
Flowmaster 50 Series.................................. ...................362
Flowmaster 40 series 43040................................... .......392
Dynomax Super Turbo................................... .................410
Flowmaster 62631................................... .......................435
Carsound Cat Converter............................... ..................436
FLP Cat Converter............................... ............................440
Edelbrock Victor 5535.................................... ..................562
Flowmaster 40 series 435409.................................. ........576
Edelbrock RPM series 5511.................................... ..........579
Flowmaster Delta Force Racing 54040-10........................634
Edelbrock 304 series 5560.................................... ...........640
Edelbrock Gen App 5505.................................... ..............708
Dynomax Race Magnum Welded 17216...........................711
Borla XR-1 40600................................... ..........................836
Borla XR-1 40615................................... ..........................854
Dynomax UltraFlow SS 17263................................... .......1000
Dynomax Race Magnum Welded 17218...........................1000
Borla XR-1 40575................................... ..........................1100
Dynomax UltraFlow............................... ...........................1133
Edelbrock Victor 5537.................................... ..................1400
Borla XR-1 40450................................... ..........................1400
Borla XR-1 40741................................... ..........................1450
Dynomax UltraFlow SS 17296, 17268..............................2200
Dynomax Race Magnum Welded 17220, 17224...............2200
Dynomax Race Magnum Welded 17225...........................2600

 

I don't think the stock exhaust is 2 1/2", but it is a nice upgrade. You won't be able to see the difference but you might be able to feel it. If you want flowmasters and headers you will have two problem areas for fitting a "bolt on" replacement exhaust system. 1. The Flowmaster mufflers will need elbows on both inlet and outlet to fit onto the exhaust pipes, and exhaust tips 2. The front section of the 2 piece exhaust pipe is designed to reach the stock exhaust manifold. If you install headers, you will have to cut off a good section of the front exhaust pipe to fit onto the headers (and you will need reducers to make the connection).

I replaced my exhaust system (2.5", but my original exhaust in 68 was 2.5") and installed flowmasters. With the elbows it's a lot of parts. The flowmaster mufflers are a little larger than the stock mufflers so it is a tight fit. I have an extra set of front exhaust pipes that are specially cut to fit with headers. I just haven't installed the headers yet. MJ