DOUG S HEADERS DES104 LS Engine Swap Exhaust System Instruction Manual

Installation Instructions & Warranty Information
DES104 ~ 1970-74 GM F-Body
LS Engine Swap Exhaust System

Rev. 1 12-14-21 DSL

DES104 LS Engine Swap Exhaust System

PerTronix® thanks you for choosing DOUG’S HEADERS , the best fitting, highest quality
Header and Engine Swap products on the market. To realize the full potential of our good fit, please read and understand these instructions completely prior to starting work.
Check to make sure you received the proper parts for your application against the parts list in these instructions. If you are unsure you have received the proper parts, please call PerTronix before you start work.
Be sure to work safe! Whenever you work under the vehicle be sure that it is located on level, solid ground and is supported by adequate safety stands!

Remember: Hot asphalt will not support most jack stands!

WARNING:
This product can expose you to chemicals including Lead, Nickell, Cadmium and Chromium which are known to the State of California to cause cancer and berth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov

NOTE: Read Before Starting Installation

1. This exhaust system is designed as a bolt on system specifically for use in LS Swapped 1970-74 F-Body cars using Doug’s LS Swap Headers and mounts.
2. This system will connect to the Doug’s Headers using Doug’s motor mount brackets and Doug’s transmission crossmember, Any other brand of mounts or headers will not necessarily fit.

INSTALLATION

1. Check that all the parts are in the kit before starting. If you are unsure, contact Doug’s Tech department at 909 599-5955.

2. The LS engine and transmission swap need to be completely installed before installing this exhaust system. If you haven’t already done so, remove all existing exhaust and mounting brackets. Retain the rear tailpipe mounting bolts to the frame for re-use.

3. Raise and support the vehicle either on a chassis lift hoist or on Jack Stands so that the rear suspension is at full droop.

4. Slip one 3” Accu Seal Clamp over each inlet side (short side) of the X Pipe. Slide the header to X-Pipe mid pipes into the X-Pipe (they are marked Driver and Passenger side). Do not fully tighten the clamps.

5. Install the entire assembly to the Long Tube Headers using one V-Band Clamp on each side. If you are running the Doug’s Mid Length headers, you will need to install the Doug’s mid pipes, part #DMP104 (sold separately) to connect the exhaust to the headers. The emergency brake cables should go above the pipes. Do not fully tighten the clamps.

6. Slip one 3” Accu Seal clamp over the offset end of the mufflers and slide the mufflers onto the outlet side of the X-Pipe. Do not fully tighten the clamps.

7. Slip the over axle tubes in place from the front side of the axle. Slip one 3” Accu Seal Clamp over each inlet end and slide the pipes into the mufflers. Do not fully tighten the clamps.

8. Place one rubber isolator into each U-Channel on the tail pipe hanger brackets. Slip a supplied 1/2 Bolt through the bracket and the isolator and then place the square back up plate (washer) onto the rubber and secure with the 1/2 Nut. Slip the other end of the rubber isolator over the hanger rod on each tail pipe with the flat part of the bracket with the six holes facing towards the outlet end of the tail pipes.

9. Slip a 3” Accu Seal clamp over the inlet end of the tail pipes and slip them onto the over axle pipes.
   Do not fully tighten the clamps at this time.

10. Attach the hanger bracket to the out side of the frame using the factory holes in the frame with the original factory fasteners.

11. You will need to support the mufflers up into final position using jacks or stands. The muffler will need to be rotated slightly so that the side nearest the Driveshaft is higher at about a 15° angle, This will bring the over axle and tail pipes up to the proper position.

12. The muffler brackets will attach to the floor pan, the easiest method is to use 3/16” x .425” Stainless Pop rivets. This is not the strongest method and you might consider drilling the mounting holes in the brackets to 1/4” and using nuts and bolts (which will require taking the back seat out). Alternatively you can plug weld the bracket directly to the floor pan (which also requires seat removal to mitigate the chance of fire).

13. Once you have decided which mounting method you are going to use, connect the left and right muffler brackets to the hanger rods on the over axle pipes using the rubber isolators.

14. When you have the system raised and the mufflers rotated properly, the brackets will line up with the crease in the floor pan where the seat belt attachment well is. See Photo.
    

15. Once you have the exhaust raised into position and the brackets in place as shown, drill the holes for either the rivets or 1/4” bolts that you decided on and fasten in place. Do Not drill if you decided to plug weld.

16. Carefully align all the pipes and the mufflers for the best fit and appearance. Tighten each clamp working from the front rearward. Pay attention to the fit and you may need to loosen a previous clamp as you work your way back to keep the proper alignment. Exercise patience and care to get the best fit. Pay special attention to the over axle pipes and their relationship to the rear control arms and springs.

17. Tighten the V-Band clamps by hand (do not use air) so they are tight, use care to keep from stripping the nuts. Tighten all the Accu Seal clamps to 60 lb ft.

18. Congratulations, you are done. Check all clamps and fasteners after about 50 miles and again once a year.

This product is designed for swapping a non-original engine into a vehicle that did not offer it. Laws vary by state regarding emissions regulations for engine swaps. This product is Illegal for Street or Off Highway use on any 1975 or newer vehicle originally equipped with a catalytic converter and may further be illegal depending on state or federal engine swap emissions laws regardless of vehicle year and would therefore only be legal for Closed Course Competition use. PorTronix Performance Brands 2021

DOUG’S HEADERS LIMITED WARRANTY

All Doug’s Headers and Exhaust products are guaranteed, to the original purchaser, to be free of defects in material and workmanship for one year from date of purchase. This warranty covers the replacement or repair of the product and does not cover the cost of removal and installation, customer applied coatings, or Any discoloration or corrosion of finished surfaces. Damage or product failure resulting from collision, improper installation, off road use, road hazards, the use of exhaust insulating wrap, or rust occurring after installation is not covered by the warranty. This warranty extends only to the original purchaser. Should a part be deemed defective, it should be returned to the original selling retailer and must be accompanied by the sales receipt. If there is no retailer in your area, contact PerTronix direct for a return authorization and return the part prepaid to the factory for inspection.
PerTronix reserves the right to replace or repair the alleged defective part and return the part freight collect.

Parts List

A PerTronix Performance Brand ~ www.pertronixbrands.com ~ 909 399-5955

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