Cam timing & springs

[djwilk]

Sorry about yet another thread,

On the Coleys timing kit, is it worth advancing timing for better low end torque?
The cam being used is XER273HR.

Also, whilst changing springs how do I determine top piston position? Spark out?

[ringram]

Cam may or may not have timing ground in.
So you need to know that. Though in theory if you have a cam wheel you would use that to find the intake center line and adjust from there.

If the cam is 114 LSA then 110 ICL is normal. Aka 4* Advanced but you can retard it for more top end. It should lift high rpm torque but drop low rpm torgue to more you retard it.

Assuming cam grind is good you could install it dot to dot. Which should match the cam card with whatever advanced the ground in.
But check p2v to make sure you have at min 2mm clearance on intake and 2.5mm on exhaust. Most will want to see more than that.

[djwilk]

Rich,
The cam is as above, with under .600 lift so should be ok for clearance right?

[ringram]

If its a per the cam card.. http://www.compcams.com/Company/CC/cam-specs/Detai...

And you install it properly with the 2* advance it mentions then you should have no issue. Its not lift that affects p2v its IVO and EVC

[ringram]

... if you are swapping springs put a light check type spring on one cylinder and check p2v around TDC on intake and exhaust.

Yanks say around 230* is about max on the LS3. But you should check anyway.

[MyM8V8]

To check P2V I used blu tack on the piston crown, re fitted the head and turned it over. Cut the blu tack across and measure the depth of it to make sure you have enough clearance. IIRC its 80 thou but you need to do you own research.

[djwilk]

I'm not taking heads, doing it in situ...