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1978 Jeep CJ 7 - Muddy Horses

Mud Bogging
Pete Trasborg
| Brand Manager, Jp
Posted April 11, 2007

A CJ For The Slop

We were in Michigan for a three-day weekend crammed with wheeling, and we saw a Jeep or two in that time span. This one, in particular, caught our attention when it fired up because we just love the sound of a healthy 401 V-8 in a Jeep.

After John Copeman took a few passes by us, we were hooked and had to see more. Within minutes, we were shocked to learn that this healthy-sounding Jeep "only" had a 304 in it. We didn't buy into it for a second, and even after seeing the "304" cast into the block, we were still skeptical.

As we found out over the course of the weekend, while this is a Jeep built for mud, there is a lot of thought put into making it go in the goo.

Hard Facts
Vehicle:'78 CJ-7
Engine:'78 337-ci AMC V-8
Transmission:'74 TH400
Transfer Case:'78 Dana 20
Suspension:Spring-over on 211/42-inch lift springs
Axles:'81 Dodge Dana 60 (front); '75 J-20 Dana 60 (rear)Wheels:15x12 Eagle 589
Tires:18/39.5-15 Super Swamper Boggers
Built For:Mud
Estimated's still growing

Chassis and Driveline
It all starts with the deceptive AMC 304. John had a ton of work done to it by Checkmate Racing in Waterford, Michigan. The "304" is really now a blueprinted and balanced 337-ci AMC V-8. The pistons are from TRW and originally intended for a 0.040 over Chevy 305, a custom crank gets it the rest of the way to 337-ci with a compression ratio of 10.5:1. A healthy cam was stabbed into it while the heads got some porting and polishing done and a roller rocker conversion using Crane Gold Roller Rockers. Handling the fuel is a pair of Holley blue electric fuel pumps, Edelbrock Performer rpm intake, and a 750-cfm Barry Grant Demon carburetor. Hedman Fenderwell headers dump the exhaust through 3-inch diameter pipe and a pair of single chamber Flowmaster mufflers. An MSD 6AL ignition works with a pro billet distributor and an MSD adjustable advance box to provide the spark and keep from detonating the engine. If all that wasn't enough, the Jeep has an NOS super power shot and purge kit for a little extra oomph.

All that power is harnessed by a TH400 modified with a B&M manual reverse valvebody, B&M 2,400 rpm stall speed Hole Shot torque converter and topped off with a B&M Mega Shifter. From there, it goes to a relatively stock Dana 20 transfer case with 1,350 yokes and custom driveshafts to take the power to the axles. Up front is a narrowed Dana 60 with a Detroit Locker, 4.88 gears, 35-spline Moser shafts while the rear is a Dana 60 with 4.88 gears, full spool, and matching 35-spline Moser shafts. Both axles have been converted to 5-on-5 1/2-inch bolt pattern for that stock Jeep look with Chevy discs on the front and Ford Explorer binders slowing the rear down.

As you might expect, goo slinging is left to a quartet of Super Swamper Boggers in the 18/39.5-15 flavor wrapped around 15x12 Eagle 589s. Fuel comes from a 9-gallon fuel cell, so John has to stay near a gas can at all times. With the power this thing is making and the fuel it has to burn to make that power, it sips gas through a biiiig straw. The suspension lift comes thanks to a spring-over conversion done with 2 1/2-inch Skyjacker lift springs in the front and stock '91 Blazer springs in the rear. Damping is handled by a Rancho RS 9000 at each corner.


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