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If you recall, the last time we took project ’67 to the track, it was the maiden voyage for the new 331 stroker engine. That day turned out to be very encouraging, as we cam home with a 11.87 ET at 117 mph. Since then we've only made six more passes on the new motor -bringing us to a grand total of 10 passes so far.

We knew that there was more in the motor, especially considering the 1.59 60fts, but we were weary of the stock 28 spline 8” axles. We had already snapped one with the previous motor, and on a test drive shortly after installing the 331, we found twisted splines on the drive side axle. It became readily apparent that we had to address the issue of axle strength. Unfortunately the 8” Ford differential is limited physically to a 28 spline axle, unlike it’s 9” big brother which can accommodate up to 40 splines.

Round 2
Nevertheless we put it on out to-do list to research the options. In the meanwhile we were dying to get to another track session. We made our way to a test and tune, and got fired up about the prospects of dialing in carb jetting and timing. The first pass showed promise. Launching the car at an axle-sparing 2500rpm, we had 1.7 60ft and still ran 12.00 @ 118. With plenty of traction coming in the way of ET Drags, we figured the next run would show a nice high 11 sec timeslip if we raised the launch rpm to 3000.

The next run started off in the right direction. A 1.62 sixty-foot time flashed up on the board. The 1-2 shift was nailed, and then it was over… the nose of the car dived down, and the engine acted as if it hit the rev limiter. The run was over, and now the question was what broke. A quick glance at the gauges indicated no problems with oil pressure or water. However the engine was at a constant sputter, not wanting to rev past 1500. I limped the car off the return road and back in to the pits.

My initial feeling was that something in the ignition system failed. Perhaps the MSD box or distributor decided to go out. However after checking for spark at all eight cylinders, and pulling and inspecting the distributor, no glaring problems were noticed. Next step was to suspect a broken valve spring. Pulling the valve covers revealed the problem – a broken rocker arm stud on the # 7 exhaust valve. Who would have ever expected a 7/16” rocker arm stud to break? Not us… hence we didn’t bring a spare. In fact judging by the fact that no one at the track seemed to have a spare stud, we concluded this was a rare event and perhaps we just had a bad stud to begin with. After rigging up the stud so that it would work, we drove the car home –gingerly, keeping rpms below 2000 rpm the entire way. The stud would be replaced, and we’d cross our fingers that this wouldn’t occur again. After all, a stud girdle is an option, but realistically a hydraulic roller cam with .550 lift should not warrant one.

Round 3
In the mean time we came to a decision on our axle issue. Rather than spend the $1000 or so it would require to build a full 9” rear end, we decided to push our luck and order a set of hardened 28 spline axles. After doing some research, we opted for a set of Dutchman 28 spline axles. Dutchman gave us fair warning that for the level of power we’re making, we should really be using a 31 spline 9” rear-end. They stated that their 28 spline hardened axle would be about 25% stronger than stock. We figured that since we weren’t shearing this things upon every launch, that 25% should provide an adequate margin of safety. In general axles for race use should have a 200% margin of safety per axle– i.e. an engine making 400 ft.lbs. of torque, with a 4.11 rear gear and 3.35 first gear is making 5500 ft.lbs. to the axles (or 2250 ft.lbs. per axle) and thus should use an axle capable of handling 5,500 ft.lbs. (a 31 spline hardened axle can generally handle 6400 ft.lbs. of torque, a 35 spline can handle 9600 ft.lbs.)

The following weekend we headed back up to the track. The Dutchman axles installed as easy as advertised, and looked like being capable of handling some serious launches. The three passes we’d make that day would prove our hunch correct. Our best pass would be a 11.72 @ 118.8 with an outstanding 1.56 60ft. This is a car using stock 4-leaf springs, eight year old Monroe replacement shocks, and $99 under-ride traction bars. We’re dumping the Spec Stage 3 clutch at 4500 rpm, and the car handles it like its pulling out of the car wash on a Sunday afternoon. It launches so smooth that it’s hard to believe the short times that flash up on the score board.



With less than a dozen passes on the new motor, and each pass getting subsequently faster, we're indeed very pleased with the results of the 331. What is more impressive is that the motor is very streetable -offering nearly 12 mpg on the 120 mile round-trip drive to and from the race track.

The next steps call for some chassis dyno time to nail in the timing and fuel tuning, and then let our resident hot shoe Victor Silva pilot the car -if history is any indicator, his talents should put the car smack in the middle of the 11's. F/M


We decided to postpone a full 9" rear end buildup for now. These 28 spline hardened axles from Dutchman should give us 20-25% more strength.
 

We've snapped a stock axle at the splines, and this one that came out looked as if it was headed down the same path. The Dutchman axle on the left is visually beefier at the splined end.
 

We ordered the axles with studs and bearing pressed on, making for a "plug and play" installation.
 

We spent a few more bucks to have the flanges drilled and tapped for 1.5" long studs (NHRA tracks typically require rear wheel studs stick out past the lug nut end.)
 

With the drum off we removed the axle retaining flange nuts.
 

A drum can make for a quick and easy axle puller: Flip the drum around and attach a few lug nuts loosely and yank.
 

Slide the old axle out. Now's the time to replace axles seals if they are leaking.
 

Slide the new axle right in. We were impressed with how the Dutchman axles fit perfectly per our measurements taken over the phone. No surprises or fitment issues to deal with.
 

Install the supplied retaining plate and it's off to the track for some abuse!
 
Contact:

Dutchman Motorsports, Inc.
http://www.dutchmanms.com/
P.O. Box 20505
Portland, OR 97294
503.257.6604


 

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