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Paul M

Well-known member
Jun 6, 2022
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My Car
73 loaded Q code car w/a 351 4v C6 it came with 2 cars in parts.
I'm semi retired; which means that I spend an average of 50 hrs a week working on various car projects. I've been doing a complete rebuild of a 73 Mach 1. I bought 2 cars in parts and have been selling off parts to assist in the build price. I started out with a Q code 73 Mach1 & am selecting the best parts for the project. It came as a brown on brown car. I switched out the interior to a black interior that is loaded with all the features I'd ever want. I ended up painting it Grabber blue w/ black accents. I switched out the front fenders and converted the "heavy" 73 urethane bumper n brackets to a 71 assy. in order to save @ 100lbs of weight. I have detailed photos w/descriptions of every stage of the project. I built the C6 w/mods necessary to handle up to 500 hp. The 351 4V motor is utilizing features like H beam rods and forged pistons. This was a loaded car, however, even with the factory high output suspension package it doesn't have a posi. I will be adding a posi with a 3:91 gear. If you have any problem areas with your own build, I covered all of the car. I do all of the work myself, except machine work and front end alignment.


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Hello and Welcome from Michigan. The suspension is actually called competition suspension, for your future reference. Track loc rear ends were an option. If an a/c car the tallest gear available was the 3.25, which could be open or posi. A 3.91 rear gear will be fun! Good luck with everything and have fun!
Greetings, from Upstate Western NY (Pittsford, a suburb of Rochester)! Out here we (also) have a 1973 Mach 1. Its powertrain is a bit milder than yours, where the prior owner replaced the factory 302 with a 1994 F-150 351W, using heads from a 1969 351W 4v. The compression with a set of forged aluminum pistons was kept to 9.5:1 due to the low octane ethanol free gasoline out here (89-90). He also swapped out the original 2.79:1 rear axle gear set with a 3.5:1 TractionLok unit. The original front drum brake system was replaced with a wrecked 73 Mustang's disc brakes and master cylinder. After the 351W was dropped in the engine produced 360HP. Not a ferocious amount, but plenty for some spirited driving.

We did some upgrades also, to include installing an aluminum radiator and dual electric fans. The original c4 began to slip with its 1-2 upshifts at WOT. Rather than rebuild the C4 we opted to swap in an AOD that was set up a firmer shoft than the factory setup. I also set the Throttle Valve pressure to 39 PSI vs the factory 30-35 PSI, in order to get firmer upshifts are higher road speeds on light acceleration. Our engine RPM at 60 MPH dropped from 2,850 to a mere 1,850, making the Mach 1 a lot more fun to drive for more than 20 minutes, as the engine running at 2,850 was fun for a while. But after about half an hour or so it grated on me. With the AOD I retain the lower end performance we had with the C4, then getting great performance in 4th/OD gear. With the engine built for higher than stock performance, the Mach 1's top end is higher as the torque and horsepower to overcome air resistance is on tap at higher RPMs and higher road speeds.

We also have a well preserved, true survivor, real barn find 1973 Mustang Convertible. It was literally barn stored out here for over 40 years. We have done a few modifications, not huge. The powertrain is the original 302/C4/2.79:1 configuration. The vehicle has an original 21,000 miles on it, and has its original exterior finish and interior panels. Although it is not m our most powerful pony car, it is still a blast to drive. As with our 73 Mach 1 we added a Classic Air air conditioning system, which makes both cars a lot more fun to drive in the warmer and hot months.

The rest of our little fleet of pony/muscle/sports cars is a 1969 Shelby GT500 (my favorite car of all), a 1997 Honda Del Sol SI, and a 2020 Shelby GT500. Sadly, Car Season out here is only from mid-April - early November. The other months bring snow and ice, and salt on the roads. So, the pony cars are in Winter Hibernation until later this year.

I look forward to seeing more photos and details of your car(s). Keep safe..


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