Pinion Pain

I have a 1972 Charger with an 83⁄4 rear. The centersection is a 489 case with 3.55 gears. I am running a stock-stroke 400 big block with the usual bolt on parts, higher compression pistons, and Edelbrock heads. The engine makes about 430 horsepower. The transmission is a factory 727 with a 3,000-rpm stall convertor and shift kit. When I was racing a buddy, I suddenly got a driveline vibration and noise. I pulled off the road expecting to see a broken or loose u-joint, but found the pinion nut had backed off.

The rear was never rebuilt, but it has a cone-clutch Sure Grip. I was able to just tighten the pinion nut and drive back home, but I'm worried about it coming loose again. If I just retighten the nut with red Loctite, do you think it will hold? A friend of mine says the 742 case is better, and I need to swap the center section out to avoid any more trouble. Any advice is appreciated.

Rusty Moore
Via moparmuscle.com

Rusty, the thing about the 489 case is that it uses a crush sleeve at the pinion to set the preload on the pinion bearings. The problem is that once the crush sleeve loses tension, so does the pinion nut, and from there things fall apart, literally. If you retorque the pinion nut, the bearing preload will likely be too tight before you even get enough torque on the nut to hold the assembly together. Loctite is not really a solution, because you really need the proper torque to retain things, not glue on the threads. A pinion nut failure can lead to a locked rear end, and that can spell disaster on the road.

In contrast, the earlier 742 gear set uses a spacer and shims to set the pinion bearing preload, and that arrangement cannot unload the pinion nut. This is much more reliable than a crush sleeve, but you don't need to change your 489 carrier. While you could just rebuild the 489 with a new crush sleeve, the better bet is to retrofit it with a solid spacer and shim arrangement similar to the earlier carrier. The parts from the earlier rears do not interchange, but most rear end supply companies can supply a retrofit solid spacer kit for the 489 case.


Ignition Options

Will the Pertronix system be an advantage over the standard system? I feel it will be a better system. The vacuum system will still be used. This will delete a few troubling components. What do you think? I believe in the KISS system (Keep It Simple Stupid). What do you think? I have two 360's in two different cars!

Joe Waldrop
Via moparmuscle.com

Joe, thankfully there are many options in ignition systems for our classic Mopars, and the Pertronix is a good one. I've used these, and the advantage is as you say a simple, self-contained ignition with minimal wiring. In my experience, these are effective and reliable. You did not say which "standard" ignition system you are comparing to, but if your other option is points, the electronic Pertronix definitely has advantages.

Retainer Replacement

I have a 1977 half ton Dodge D100 fleet side that I have built up into a "muscle truck." The engine is a 360 that is bored .030-inch over with Ross flat-top pistons, with a stock 360 crankshaft and rods. The heads are a set of Mopar Performance Large Port Commandos, fully ported, and flowing over 300 cfm on the intake side. The intake manifold is an Edelbrock Super Victor topped with a Holley 950 HP carb. I'm running a custom Comp Cams solid-lifter cam with 242-degress duration at .050-inch, and almost .600-inch lift. The engine makes great power, and pulls to 7,000 rpm. I drive the snot out of this truck, and use it as daily transportation. I've put over 30,000 miles on this engine since I built it six years ago.

I went to adjust the valve lash, and something didn't look quite right. I used titanium retainers because of their lighter weight, and noticed that some of the retainers seemed to have worn at the outer step where the spring seats. What could cause this wear? My valvesprings are set up with 160 pounds of spring pressure on the seat, and 360 open. Am I not getting enough oil to the top end? I like the lightweight retainers for the high rpm capabilities, but feel like I dodged a bullet when I found this problem.

Bill Coleman
Via email

Bill, titanium retainers are usually used on race engines or in Pro-Street application that see limited mileage. You are correct with the idea that a lighter weight retainer is an advantage for high rpm, because of reduced inertia, making titanium a popular choice. The downside is titanium is not as hard as steel, and in extended street use they will wear. I've seen titanium retainers worn razor thin at the spring register. If you want to run titanium parts, make regular inspections a part of your engine service and maintenance program.

Another option to consider if extended street use is the plan is simply going back to steel retainers. The first question you need to contemplate is whether you really need the weight advantage of titanium. Keep in mind that there is a new generation of lightweight steel retainers that are comparable in weight to titanium, which would be the way I'd go in your application.


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