I am fitting the st170 valve springs to my new zetec head.

Question there are two differant lengths of spring. There is a difference of around 2mm.

The zetec is the same inlet and exhaust.

For any one wondering the st springs hav a thicker coil by 0.3mm.

Instinct tells me the longer ones are for the inlet to give extra clamping force on the bigger valves but this is a guess, any ideas ?

 

The springs have come from a lowish millage untouched head. I've just checked another head I know has had some work due to a cam belt failure and they have been mixed up so I am still non the wiser.

Two sets of springs give me the option of fitting the longer ones to both inlet and out let.

Any opinions here ?

 

Well after seing the 106gti shims on eBay it had the thicker ones on the exhaust, so I put the longer springs on the exhaust.

B#ll#x.

The longer ones don't fit the exhaust side as they bind.

 

Can't say I noticed a difference when I did mine, having said that I can't remember if I kept them all in order or stripped all from the ST170 head and then fitted to blacktop head.

 

Is yours a silvertop or a blacktop as the longer springs don't fit either inlet or exhaust on the blacktop. Twat.

For any one reading this at a later date.

My head is a 2004 2.0 Focus zetec from a crate engine.

Standard springs are all 44.5mm long.

The st170 head is from a 2002 and there are two spring lengths.

45.25mm

47mm

The 47mm are coil binding at just before full lift.

 

Blacktop, brand new head from a crate engine too, my ST170 engine was listed as a 2003 on ebay where I bought it from.

 

Hmm just a follow up, my cams are stamped sportscam. I need another look but if they are stamped kc as well as some other bits they may be Kent cams fast road cams. The extra lift may be why the springs are binding.

 

Black top work fine with st170 valve springs ....

 

I've fitted many black top heads with ST springs and never had any problems, all with stock cams though.

 

Just in case some one reads this.

I've stripped a third head and there are two lengths of valve.

The longer ones go on the exhaust and shorter on the inlet.

And they didn't work in mine due to them being high lift cams.

 

a little more info - i stripped a head at work and found the springs to be:

Inlet 45mm free length, purple paint on springs.
Exhaust 46.5mm free length, yellow paint on springs

 

Just my luck to get a free set of race cams when I wanted standard.

If I get some standard one's they will end up needing re shimming.

 

may have a set of standard ones if you want to swap?