Timing Chain Jumping

FAIZAL ASMAL

MEMBER
1973 DODGE 600
1.6L
4 CYL
RWD
MANUAL

1600GS Coupe, 4G32 Engine, South Africa
Hi,

This was my second car and it was one of my favorites but it had one constant nagging problem. Every few hundred kilometers the timing chain would jump. Eventually I figured out a way of resetting the valve timing without dismantling the timing cover and kept the required tools in the car. One day I noticed that every time you switched the car off, the engine would kick back and I suspected thatis what was causing the chain to jump. The ignition timing was not the cause of that. Do you have any ideas as to what the cause might have been?
I eventually put a 2L Mitsubishi engine in and sold the car.

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

Every engine kicks back like that. As it coasts to a stop, one of the pistons is coming up on the compression stroke. That pressure in the cylinder forces the piston back down before it ever gets to top dead center. If you watch any old war movie with airplanes with propellers, you'll see them kick back too when they come to a stop.

There was something else causing your timing chain to jump. It is true they typically jump when the engine is stopped, but that is because they are worn and stretched, the teeth are worn off the camshaft sprocket, (especially on those that have nylon teeth on a steel gear), or the cylinder head had been resurfaced multiple times. The cylinder head issue only affects timing chains and belts when the camshaft is located in or on top of the cylinder head. Resurfacing the head lowers it and shortens the distance between the crankshaft sprocket and the camshaft sprocket. That makes the chain loose. Lowering the head also raises the compression ratio. Both problems can be solved by installing a spacer between the cylinder head and engine block.