Camshafts and the timing Game.

[mick taylor]

The subject of Camshafts timing.

1 facing the front of the engine do all engines turn running clock wise ?

2 As to the cam timing with a chain or a belt, as they stretch what goes on and how much degree could this make with being out of wack with the original spec ?
I have seen a Holden V8 that the slack in the timing chain must of been easy worked out too being like one tooth out, so what degrees would that be out ?

Some camshafts have dizzy gear on them that drive the dizzy that spin the other way to others I seen on TV with a Big Block Dodge to a Small block Valiant.

So what is going on with ones spark timing on a 5.0L EFI Holden V8 if you never touched it ? as the chain stretches the dizzy spark must retard ? you would not want it to creep forward on any engine.

I seen Valiant in 1975 claim you need not touch the dizzy for 50,000KM I think it was, but in that time I am sure the timing would be out of it's original point due to the chain stretch.

Modern day engines with veritable adv and retard setups on the camshafts get to a point that a light comes up warning you to change the belt. so all must be spot on in regards to everything until then.

I retarded my cam timing on a near stock 308 Holden by 4 deg just to see if I could get a bit more top end, but all it did was loose power every where, It did not have high compression, maybe 8.8:1 I would think as it had stock blue motor pistons, I would think that being retarded cam timing that this will lower the running compression a touch if anything.
Not to mention that -4 deg cam I would have to adv my spark by 4 deg as a rule.
I should of advanced the Cam timing by 4 deg would of been a better option and maybe got a bit more grunt.

Torana LH 308 cam timing is advanced by 5 deg over a HQ 308.
HQ 308 intake timing is 27-63, LH Torana 308 is 32-58

Now from the HJ 5.0L the cam is a pollution cam as it has more exhaust duration and a late exhaust close to add more heat to the exhaust to burn more fuel in the exhaust system I believe.
Intake 28-72 exhaust 78-30 is the HJ-X-Z
27-72 71-19 is the HQ
32-58 76-14 is the LH, is this called advanced or retard over the HQ ?

When we advance the spark we are sparking before the top dead centre.

But when we are advancing the cam ? I would think it is the other way round, so 20-60 straight up and if we retard it by 5 deg it would be 25-55 ? or is it 15-65. so an old chain will be retarding the cam timing no ? and retarding the spark timing point. so if your spark timing was 5 deg, now you will need 10 deg.

A mate once had his 308 rebuilt and the dude put the Cam timing out 2 teeth out, as he thought that Chev were the same number of links apart that he worked on, this engine was gutless as but would rev out real well.