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cam timing on SOHC 8v engine.

1K views 6 replies 4 participants last post by  tomstickland 
#1 ·
I've just fitted a vernier cam pulley to my Astra GTE 8v. I'm having it set up on a rolling road some time soon.

In the meantime I'm going to play a bit and see which setting feels best. For now I've advanced the timing a bit and the car feels slower.

Can anyone remember which way does what. I think advancing the timing increases high speed torque but loses bottom end?
 
#4 ·
I played about a bit with the timing and i found that the engine ran best with the cam pully advanced one tooth clockwise. This made the engine run smoother and the sound of the air/feul going into the engine was smooth, unlike before when it was making a crackling sound allmost as if there was a bit of pre ignition.
 
#5 · (Edited)
Gander said:
Sorry for being no help what-so-ever but what is a vernier cam pulley, is it the cog that runs the cam?
It is indeed, but it is in two parts that are bolted together, an inner and outer part. This allows the adjustment of the valve timing of a few degrees either way for optimum performance.

It is called a vernier pully as it has a built in vernier gauge, basicaly a pointer and scale, so you can adjust it accuratly.
 
#7 ·
An adjustabe pulley allows the cam pulley position to be adjusted relative to the cam shaft. This means that the cam timing can be adjusted. Otherwise your only control is moving it one tooth at a time.

The one I've got has three parts to it:
1)An adaptor ring that sits on the end of the cam shaft and is located by means of a small hole that the pin on the end of the cam shaft fits into. This adaptor has 9 holes round it.

2)The pulley. This has ten holes in it. As you turn the pulley relative to the adaptor different holes line up. A small dowel goes into the pair of holes that line up.

3) A clamp ring that the bolt pulls on to hold the whole thing together.
 
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