GM A-Body Instructions For 3½" systems

(Intended for vehicles with aftermarket headers needing dual exhausts - FOR STRIP AND OFF ROAD USE ONLY ON POLLUTION CONTROLLED VEHICLES)

Included with this kit are the following:

NOTE: While this system is intended for highly modified vehicles which will most likely see track use only, we have made every effort to design it to fit well. Because of the Huge size of the tubing, it can, naturally, be somewhat more difficult to install. We know that most likely you will have to slightly "dent in" the tubing above the rear end between the coil spring and upper control arm. There is just about no other way. We know that from time to time situations will arise which will not be accounted for. To help minimize inconvenience to you, we recommend that you do some measuring, etc., before "tearing off" the old system. This way, if you have one of the exceptions, you will not have 'down time" if your vehicle is a daily driver. This will enable you to obtain the necessary parts to complete the installation.

Muffler length is generally limited to a maximum of 20" case length. Both Walker and Flowmaster muffles work equally well, however, the mufflers used need to be offset entrance and offset exit.

This is intended to be a "Slip Fit" installation. Welding is necessary for the No-Weld Collector Reducers and for the installation of the Balance or Crossover tube if purchased with the kit.

1. First begin by reading the instructions to get a good overview. Remember, safety first. Be sure vehicle is secure and that pipes can cut.

2. Compare hardware with the list above to be sure you have everything before beginning.

3. Now lets begin with the tailpipes. They must clear the suspension and the rear end, so they must be positioned first. Each tailpipe is a two-piece unit. We have left it this way to make it easier to install and easier to adapt to problem areas. Once you have "fine tuned" the fit, you may either weld the two pieces together or just simply use the clamp provided. In some situations it may be possible to use existing hangers, otherwise use what is provided with the kit. You will need to position the hangers for the mufflers directly above the rear of the muffler spout. The hangers for the end of the tailpipe can be placed anywhere along the outside of the frame. Often existing holes can be used, but you may need to drill new ones.

4. Mount the muffler onto the front of the tailpipe. You may want to temporarily secure the muffler with something placed under them. This will allow you to devote full attention to determining the correct length for the Head Pipes.

5. Mount Collector Reducer Flanges onto end of headers. Now determine the position of the tube part of the reducer and tack weld it to the flange. Then take the collector assembly off and run a bead of weld around it. Then remount on the header.

6. With mufflers in place mount the Headpipes onto the Collector Reducers and determine how much you will need to trim off. You may trim off the end of the Collector Reducer also. Remember, measure and re-measure as it's easier to trim a little more off than to add because of trimming off too much. If the Head Pipe does not reach far enough back, then you will need to do "but-weld" an extension between the end of the Headpipe and the muffler. Being short is extremely rare and then mostly on the longer wheel base vehicles such as the El Camino and Caballero. The GTO's have a tendency to come up short more so than other A-Body vehicles.

7. Fine tune the fit. Once you have trimmed the Head Pipes for proper fit, then begin "fine tuning" the overall fit of the system. Do not tighten clamps until you have everything fitting. Consider suspension movement while fine tuning.

8. Check for leaks upon completion. Normally good sealing occurs with clamp type installations. However, occasionally we run into a situation were proper sealing is difficult to obtain. If this is the case, first try tightening the clamps a little more. However, with a lot of tightening, it is possible for the pipe to start crimping or the U-Bolt to "break". OR, try relocating the clamp forward or backward from its present position and re-tightening. Another possibility is trying "muffler cement" which can be purchased from any muffler shop, or auto parts outlet, or us. If there is excessive clearance between the two pipes or muffler and pipe, then it may be necessary to cut one or more slots in the outer pipe to allow it to compress further for better sealing. Try to rotate clamps so the bolt part is not pointing downward for a cleaner looking installation.

* * If you have purchased the Walker Mufflers, please take a few moments to fill out the warranty and mail it in. Flowmaster does not require a card and does not give a specific warranty, but they do stand behind their product.

X X The above True Dual System is intended for Track or Off-road use only on Pollution Controlled Vehicles X X

 

BALANCE TUBE (CROSS OVER TUBE)

A balance tube serves as a pressure relief valve to help equalize pressure buildup in the Head Pipes. It helps the system to equalize the pulses (of exhaust and sound) that helps minimize backpressure and the sound level. It is extremely helpful on 2½" and smaller systems and highly recommended. On 3" systems it will not particularly be helpful unless you are in the 500 plus horsepower range. 3½" systems will need to be in the 600 plus Horsepower range.

 

Installation:

Ideally to determine the best mounting location, you will need to spray a line of paint on the side of the heap pipes from the collector reducer back approximately 20". With the vehicle running, you can determine at what point the paint stops burning off. This is where you want to mount the Balance Tube. If for some reason there is an obstruction prohibiting this, then mount it as close as possible to that point. We have found that usually mounting 8 - 16" from the collector works fine.

 

 

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This page last updated:  12/12/2006