[eschaider]

PHM,

A couple of thoughts on the rear end. If you choost to go the IRS route I would encourage you to use one of the many variants of the Dana 44. It could be Jag or Corvette or Viper or whatever you find that you like. The Viper is perhaps the strongest of the group because Chrysler wanted a little more warranty insurance behind 500 lbs/ft of engine torque. With that said its also worth noting that many many IRS Cobras have some variation of the Dana 44 unit under them.

If you go the IRS route, depending on your equipment choice, you ought to use the 1350 spicer u-joints or a set of the 4340 CV joints that some of the specialty shops manufacturer for the rear end. The real benefit of the IRS is the nimbleness (if there is such a word) it imparts to the car when you are driving and enjoying it the 99.99% of the time you are not at the dragstrip.

With respect to the 9" Ford. These rear ends are virtually bullet proof today all the way up to several thousand horsepower which is why you see them in the supercharged alcohol cars as a standard choice. The other reason we like them for drag cars is their pinion center is 1.375 or 1.5 (I forget which) inches lower than any other rear end choice. This lets us put the engine crankshaft centerline closer to the ground.

This is good in a drag car. In a Cobra it produces additional problems. If you use a sprung rear end with an already low pinion you produce some very nasty angles in the drive train when the body rises and the axle pushes downward on hard acceleration.

Most everyday cars have a driveshaft that is about five sometimes even six feet long. The driveshaft in my cobra is 9 inches long. This doesn't mean you can't have a sprung rear end but it does mean that the total travel of the sprung assembly will necessarily have to be either quite short or limited mechanically so you don't pull the driveshaft out of the transmission or get so close to doing so that you still get into trouble.

If you need ultimate strength notwithstanding the above you might want to look at a Dana 60. It will have a near centered pinion for good drive train alignment and it is even stronger than the 9" Ford. The ring gear is 9.75". The penalty is weight, the benefit is brute strength. These are the rear ends Chrysler put behind the four speed Street Hemis.

If you like to build strong and light and are willing to do some hunting there is a special version of the Dana 60 that was made for Blown Fuel racing. It was originally manufactured by Ramchargers who later sold the tooling to Henry's. The center section is made from magnesium with billet steel maincaps to hold the differrential in the case. The assembly is flanged at the housing where the axles enter. The flanging was used for mounting the housing, which makes it easy to put it in our cars. Then you run the IRS halfshafts (use 4340) out to the hubs and you have a truly bullet proof rear end.

For what it is worth these rear ends would take 3000HP launches all year long on 17" wide tires and come back and do it again year after year. We used to change ring and pinions at the 2 year point just to be safe. Never broke one. If you want the strongest this is it. It just takes a little hunting which is all part of the fun in building one of these cars.

In the end I think you will come down to what most of us use which is one of the many Dana 44 variants. By far the Jag is the most common. These things just work. By the way I failed to mention the 8.875 Ford IRS from the Ford Navigators. This is a light weight aluminum housing IRS that is an easy fit to our chassis and Ford goes out of their way selling the individual components through their Ford Racing Parts catalog. You can down load it from the FRPP website.

Not withstanding your intended occasional visit to the dragstrip my encouragement would be to build it as a Dana 44 IRS car. I think you will enjoy it beyond words and appreciate it everytime you turn a corner.


Ed