RETRO-TECH-4

A few subjects this time and both have been mentioned many times before but worth mentioning again. The first is the problem of plastic camshaft timing gears, first mentioned by Mike Lotwis in issue 71 and then as a question to the Jensen Car Company Ltd factory experts in issue 86.

Mike highlighted the problem that all Interceptor 383 and 440 Chrysler engines were initially fitted with the plastic (or nylon) timing gears. Due to not only heat and mileage, but also age regardless of mileage, these plastic teeth chip away and one-day the engine just doesn’t start or stops while running, bending a few push rods and valves. When enough teeth have chipped away, the timing chain just spins on the stripped gear, not allowing the camshaft to turn, thus gross mistiming.

Not only will this result in an embarrassing tow home, but also more important, a possible complete expensive engine rebuild. This is still a relevant subject as there are still engines out there that have not been overhauled and even if they are low mileage engines this is a time related problem also. The factory experts say the best way to discover if you have plastic timing gears is to remove the oil sump.

First any debris such as broken teeth can be discovered, and secondly the gear can be viewed from directly beneath, with the aid of a good light. The gear can also be viewed through the distributor-mounting hole, and then it is seen through a second oil return slot in the front of the engine. As far as we know, only the nylon-toothed type had 8 approx. 1” holes in the gear and if these can be identified then there’s a good chance that it is one of these types that you are looking at. If you do find you have a plastic gear, change it! All non-Chrysler ‘after market’ timing gears are all metal and you can also buy a Chrysler double-row roller timing chain and top & bottom gear set.

The second subject is oil leaking from the seals on the rear axle, this could be a bad seal, but Wally Hall highlighted the problem in issue 116. He found that even after a changing the seal from the nose of the differential a leak still persisted. The problem was that the differential was pressurising and blowing oil out pass the seal.

After contacting Salisbury (the makers of the unit and still existing then) they revealed that all Interceptors have a pressure relieve valve or equaliser. Its position is as follows: - If the car is on a lift, face the rear of the axle – the spare wheel is above your head. The diff. and the R/H wheel hub are connected by the axle shaft casing. Place your hand on top of the axle shaft casing, about 4” from the diff. clean the top of the shaft with a wire brush, this will reveal a hole about 1/8^th inch diameter. That is the pressure relieve valve, nothing more than a tiny hole, easily covered with dirt. As soon as this hole was cleared of ‘crud’, Wally had no more leaks. So go out and check yours.

Alan Smith