I have odd lug nuts & my oil filter blew up like a balloon

June 1, 2010 | By Richard Prince


I have a 1968 Dodge Charger and on one side of the car the tire lug nuts are left-handed threads and the other side are the normal right-handed threads. What was the reason for this?

If I change over to all disc brakes, do I have to keep this system—I say no.

Also, my Charger, with 160,000 miles on the engine (a 383 cid), did not burn a drop of oil and not had any oil leaks for all of the years that I have had it.

Then, I went to move the car into the newly finished garage in my backyard to start restoring her and when I started her up the oil pressure gauge pinned and the oil filter expanded like a balloon and cracked, and oil came out. I shut down the engine quickly and only lost about a quart of oil. What could cause this? I tried another filter—a different brand—and it did it again.

I was planning on taking the engine out anyway to freshen it up but I would

like to know what to look for once it’s out and apart.


Chrysler utilized both rightand lefthand lug threads to reduce the chance of lug nuts loosening from the rotation of the wheels while the car was being driven. In other words, they used opposite threads so that the forward rotation of the wheels would tend to tighten rather than loosen the lug nuts on both sides of the car.

You don’t have to retain this original configuration, and the fact that the vast majority of vehicles on the road use righthand threaded lugs on all wheels does indicate that when studs, nuts, and wheels are all in good condition and nuts are properly torqued they will not loosen from wheel rotation while the vehicle is being driven.

The pinned oil pressure gauge and bulging filter both indicate that the oil in your engine was excessively pressurized. This usually results when the pressure regulating valve has failed. Normally, the oil pump in your engine provides oil at greater pressure and greater volume than is required or wanted. The pressure regulating valve opens and closes in response to oil pressure and if it’s working properly, oil pressure and volume are kept within a desirable range.

It sounds as though your valve got stuck in the closed or near-closed position. This would prevent the excess pressure from “bleeding off” before it reached the gauge, filter and rest of the engine. The pressure regulating valve is a simple design that’s normally part of the oil pump. The valve relies on a ball or plunger and spring.

As oil pressure increases, it overcomes the spring’s tension and lifts the ball or plunger off its seat, thus allowing oil to bleed off and return to the sump without going through the engine. The simple design adds to the valve’s reliability but as you’ve experienced, they can get stuck.

Rather than messing around with the valve, you probably are better off replacing the whole oil pump with a new one while the engine is out and apart.

None of my ammeters work

I hope you can help me fix my wide ranging problem with Ford ammeters. We own three 1967 Mustangs, a 1969 Cougar and a 1974 Cougar. All of these cars have the same problem—the ammeter does not work. The needle perceptibly tries to move, but there is no reading!

I suspect that there is a parallel circuit containing the ammeter with a shunt in

each of these cars. I know this to be true on our 1972 Chevy pickup. GM cars have no visible external voltage regulator after 1972. What has Ford done that has made this happen?

I have been advised by well-meaning friends that the alternator/regulator has a built-in shunt and a dedicated wire, which carries current through the ammeter. We have replaced the alternator on each of these cars with a rebuilt one from the local auto parts places. Also, I have replaced what I think is the external voltage regulator on these cars. Then, there is an extra wire terminal post that is unused on these rebuilt Ford alternators that we have bought and installed. The cars all run, on and on, and the batteries stay up.

When these engines are not running, the battery voltage measures 12 volts or less. When the engine is started up and running, the battery voltage measures an increased value, near 13 volts. Therefore, the battery must be charging.

However, I do not want to be stuck on the roadside on the way to something important when I am blissfully ignorant as to whether the battery is charging or not. On older cars, for example our 1957 model, there was no parallel circuit and all the current went directly through the ammeter. If the ammeter itself died, the charging rate ended and the battery slowly went dead. The parallel circuit with ammeter and shunted wire was a brilliant design. The ammeter had no “units” thereon, but it was a wonderful design concept.


Some ammeters are connected in series with the battery and the power supplied throughout the vehicle. It measures the volume and direction of current flow and because it is in series a lot of current normally flows through it. This requires a large gauge wire and, in the opinion of some, increases the risk of an electrical fire. As you point out, a failed ammeter usually meant a near total failure in the vehicle’s electrical system. For these reasons, electrical engineers devised a different arrangement for ammeters. By placing a low-value resistor (also called a shunt) in series with the battery and the vehicle’s electrical system and then measuring the current strength and direction with an ammeter wired parallel to the resistor, the ammeter could indicate the health of the charging system without the need to feed a lot of power through it. Ironically, this second configuration actually increased the risk of electrical fire in some instances. If the shunt breaks, the current may take the only alternate route, which is through the small gauge wire that runs to the ammeter. This small wire was not intended to carry a heavy load and can easily overheat.

The ammeters in your Fords are wired in parallel to shunts and they measure the strength and direction of current flow indirectly. It is typical for the needles to move very little in either direction when the charging and electrical systems are operating normally. It takes a serious under or over-charging condition to get the needle to move significantly.

If you want a clearer indication of how the charging systems in your cars are working, your best bet is to install voltmeters. You can simply install aftermarket voltmeters and conceal them if the appearance bothers you or you can have your original ammeters modified to function as voltmeters while still looking like OEM ammeters.

Several gauge specialists, including D&M Restorations (dandmrestoration.com) offer this service.