Maxjax with a 69 Stang

[Mach1 Driver 560]

69 351w Mustang and Maxjax.

12/20/15, Dannmar has apparently recently changed the lift arms on the Maxjax. Instead of the square pads, now they are 5†diameter round pads. The arm lengths have also changed: from the centerline of the arm pivot to the end of the pad is 29†minimum and 42.5†maximum. The max is shorter and the min is greater making the lift much less flexible.

To calculate the balance point of the car you need to know the front and rear axle weights. I got this from an article on a 69 428 Cobra Jet that was complaining bitterly about the front axle weight being 2140 lbs with a total weight of 3607. Since the 351w weighs in at 3175, I subtracted the difference and came up with a front axle weight of 1787 (W1), and a rear axle weight of 1467 (W2) for a 351w. The distance from the front bumper to the front axle is 37.375†(D1), and 145.375 (D2) to the rear. The formula is:

(W1xD1)+(W2xD2)= total moment. That equals 86.065†from the front bumper to the center of balance, or where the center of the lift posts should be.

You want to balance the car on the lift or you will unduly stress the concrete that is supporting everything. The distance between the jack posts for me is determined by the minimum arm length and jack points on my other car. If you position the Stang at the balance point, the rear lift arms won’t reach to the rear frame rails by the spring hangers, so I am forced to use the rear jacking point on the pinchweld. Yes I still have the original jacking sticker in the trunk. You can buy special pucks/pads that have a grove in them for the pinchweld, and Dannmar recommends this over a chunk of wood with a groove. Since the front pinchweld jacking point is so close to the tipping point, I use the front frame rail with the lift arm fully extended. I still don’t feel comfortable with this and use tall jack stands front and back to stabilize everything. I do feel comfortable using the pinchwelds for support on this 46 year old car because the car and I lived our lifes in sunny California for all but 1 of the last 46 years and it has very little rust- probably less than me. My Stang is disassembled at the moment so I can’t take it to the nearest public scales. If someone wants to fine-tune this calculation, give me the axle weights and fuel level with no people. Gas weighs about 6 lbs/gal, so a full tank can be like having a teenager in your trunk!

I wrote this in Word and have a nice CAD drawing showing all these relationships, but for some reason I can't get the graphic to copy into this post. I converted it from CAD into a windows meta file. and all is visible in Word, but not here. Perhaps you can see it in the attachment.

69 351w Mustang and Maxjax.doc