Skyline Owners Forum banner

1 - 4 of 4 Posts

·
Banned
Joined
·
5,443 Posts
Discussion Starter #1
I know i dont own a Skyline, but could somebody help me here please.

I have just ordered a set of HKS cams and them adjustable pulley type things.

They are 256º duration (I think) and are meant to be 'mild' cams. could you let me know what this duration business means and also what difference i may notice once they have been fitted. I have a rough understanding of this, but would like have this confirmed. I assume they allow the valves to lift higher/for longer to allow more flow through them?

Also guessing that as the head has been polished, the cams & polishing will be a a real benefit to the flow of gasses and stuff.

Also whats this retarding and advancing all about?
 

·
Registered
Joined
·
3,716 Posts
blimey you dont want much do you...
 

·
Opinionated *unt
Joined
·
1,593 Posts
I don't own a skyline either, I also don't have any valves or cams, I will answer your question though.

Think of a cam as a creme egg shaped piece of metal with a stick through it. It has a round bit and a pointy bit and it turns round and round.

As it reaches the pointy bit, the followed on the cam pushes the push rod and opens a valve. When the pointy bit finishes the valve springs shut.

So the rotation and positioning of the cams, on the camshaft control the opening/closing of all the valves. The speed of the camshaft is controlled by the cambelt (or timing belt) but I'm sure you know what one of those is.

By putting a little bit of extra pointy bit on the cam you can change the timing so the valve opens quicker, opens longer, closes quicker etc. For max performance the intake valve will slam shut at the latest possible moment etc.

Retarding/advancing is all about the "timing". The cam timing has to be careful tuned with the ignition timing. Just at the point of maximum compression, the spark is sent into the combustion chamber and the bang forces out the piston. Then, at the perfect time the exhaust valve is opened.

When you retard or advance the ignition timing, the spark is sent earlier or later. If the timing is wrong you can get detonation.

Any questions?
 
1 - 4 of 4 Posts
Top