In this article I'll show you the steps I went through to add a new exhaust system to FordMuscle's 1978 F250 4x4. Also known as Project Redneck, this F250 has a nearly stock 351M with nothing more than convenient upgrades like an Edelbrock Performer intake, 4-barrel Holley Truck Avenger carb, and a Duraspark with a Mallory 6EZ. While these upgrades were an improvement, they were just not seeing their full potential with the current exhaust system.
One look underneath the F250 revealed a "Flowmaster" exhaust system. I placed "Flowmaster" in quotes because that's what was attached to the stock 2 inch pipe, factory original catalytic converter, and iron manifolds. Instead of carrying on with this half-baked setup, I decided to use Flowmaster's 2.5" U-Fit Dual Kit, Hooker headers, and Flowmaster's Big Block 70-Series Mufflers to build a real exhaust system for the truck.
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Figure 1: Here's a before shot showing the OEM cat and Flowmaster muffler.
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Figure 2: Even though the pipe originated as a 2-inch system, it miraculously ended at this 3.5-inch tip. Begging the question, how come full-size truck owners can get away with this but import owners can't? Let's teach 'em both a thing or two with some education from the from the muscle car scene... your tailpipe diameter should represent the diameter of your entire system. No posers.
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Figure 3: The stock manifolds joined immediately at this 2-inch union
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Figure 4: No question about it, out with the stock cast iron manifolds. They were easy to remove in my case since the truck only had 70,000 miles and has spent most of its life in California. The manifolds were cracked anyway.
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Figure 5: A Sawz-All underneath made for easy removal of the current pipes.
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Figure 6: This shot shows the entire exhaust system removed. You can see the variation in pipe diameter.
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Figure 7: The aftermarket has a good selection of headers for 1973-1979 Ford trucks. Hedman, Dynomax, Hooker, Summit, and Flowtech all have their offerings. I went with the Hooker Competition headers since they've always been good to me on other applications. However, neither side went in easy. Shown here is the driver's side after I removed the master cylinder, power steering pump, and the clutch linkage. And that was the easy side!
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Figure 8: I used my engine hoist to raise the motor off the motor mount towers. I unbolted the two piece motor mounts on both the passenger and driver's side of course.
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Figure 9: With patience and a dose of trial-and-error, I was able to almost get the passenger side header into place.
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Figure 10: A heat shield attached to the underside of the cab on the passenger side prevented the header from registering. I removed it since I trusted my instinct that this was some kind of compensation for the addition of catalytic converters. I wouldn't be running cats since I live in Nevada (sniffer test only for pre-1980 vehciles).
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Figure 11: Here's a closer shot of the 'lil troublemaker.
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Figure 12: The guys over at the "Dentside" forum of Ford Truck Enthusiasts website warned me about this one when using the Hooker headers. See the 3-bolt flange interfering with the shackle? I figured my exhaust guy could take care of the problem. He did.
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Figure 13: This is the 2.5-inch U-Fit Dual Kit from Flowmaster. It uses mandrel bent tubing and offers nearly everything you need to build your own system. For the multi-talented and ambitious this can be a good home project. However, after seeing where these headers dumped, I knew this era of Ford F250 would be needing a few unique bends and the experience of a good exhaust man. The kit retails for under $200.
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Figure 14: I went with Flowmaster's mild long chamber 70-Series mufflers.
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Figure 15: Here's a shot showing the installed system after taking the truck and the kit to my local exhaust shop. Danny Evans, owner and operator of Sparks Muffler, did the job. On a side note, I'm getting too old for driving to exhuast shops with open headers! Besides, I broke down on the way until I figured out I had my firing order out of wack.
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Figure 16: The F250 chassis forces a quick jog to the left from the driver's side header. If you run "inboard" headers like the Hooker's then this is a mandatory switch. Hedman makes "outboard' headers that run outside the frame rails. Outboards allow you to run straight pipes all the way back.
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Figure 17: This shot shows the parallel and adjacent nature of this exhaust system
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Figure 18: Looks good but I think the tail pipes need a scarf cut. What do you think?
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Parts and Service List
Hooker Headers PN 6902
Typical retail price - $180.00 pair
Flowmaster U-Fit Dual Kit PN 15936
Typical retail price - $200.00 kit
Flowmaster 70-Series Big Block Mufflers PN 52571
Typical retail price - $113.00 each
Local exhaust work perfomed by Danny Evans of Sparks Muffler
$200.00
Video and Audio
There's no sense showing an exhaust install without some sound. The mild sounding exhaust fits the application quite well, proving that not all Flowmaster mufflers can be treated equal.
Conclusion
No doubt, the trip home from the exhaust shop showed an immediate "seat-of-the-pants" increase in low and mid range torque, even with the underpowered 351M. Something tells me that the bad wrap the 351M has lived with for years has been primarily due to smog systems rather than the motor itself. Removing the old exhaust system was the last step in completely ridding Project Redneck of all its' smog gear.
