Deciphering cam specs??

[Stav]

What do all the numbers mean? I am confused!! What is important in reading cam cards to chosing one?

[jonbays]

The lift is the easy one stock AU has 0.444" on the inlet and 0.476" on the exhaust.
More is better! over 0.500" look for HD valve springs to stop valve float.

Inlet and exhaust duration and overlap or LSA lobe separation are the key things and what works with different mods here is quite debatable.

Stock LSA is 119 it means 600rpm idle with all accessories and so on.
LSA fom 110-114 is usually acceptable for street cars and stock ecu's hate any less than 114.

Duration is the tricky one as effective duration at a specified lift is whats important not the ramp to lift the valve off the seat and shut it on the seat gently. So various grinders use different lifts for their effective duration or advertisied duration.

under 200 is mild 200-220 is street strip and over is custome application.

[Stav]

I know of a car with 515 lift and runs standard springs..also ran a 14.2. I think the AU springs can take more than earlier ones

[jonbays]

Nahh don't believe it AU springs are weak as . You want some some good AUII ones cause I still have them and they are weak as.

[xr8ute]

Originally Posted by useless

I know of a car with 515 lift and runs standard springs..also ran a 14.2. I think the AU springs can take more than earlier ones

Just because it "works" doesn't make it a good idea. I can tell you what happens when valve springs break (read: $$$$) ;)

How good are the std retainers and valve locks? They can let go too...

The cam card should include the required spring pressures, with values for closed and full lift pressures.

You dont really know if the spring is providing the advertised pressure and rate, unless you measure it. Even then, over time, the spring rate can change...

If you are going to run std springs, at least measure the spring rate, and their pressure at the installed height, and for all of them, not just one. Then check for things like coil bind at max lift.

Then you can measure hydraulic lifter plunger depression, and rocker to valve-stem contact, and set these up properly too.

There is power to be made (or rather "recovered") by setting up the top-end of the motor properly

[jonbays]

easier to just buy the kit from Jim Mock like I did you get the springs retainers all the bits you need to make it a no worry exercise to just sit it on the rev limiter any time you like.

Or wait for the bang which may or may not be coming to a head near you

[Stav]

What does 300 duration mean?

Also my head should be ready in a few weeks to get going.Maybe chuck some super springs on there then.

[ratter]

Duration itself does not control how hard valves close as mentioned earlier.

Duration is the amount of crankshaft degrees the valve is of the seat for, the higher the duration the longer a valve is opened for, but be careful, some manufactures give duration as from .050" valve lift and some give it as adverised duration.
To "cushion" the valve when closing or to stop it from opening to sharply a lobe is designed with opening and closing ramps built into the profile, these ramps would take up some of the advertised duration.

[Stav]

What would be some recommended spec limits for my hi stall au auto? Where would I get into trouble?

[Walkinshaw]

stock ECU?

Stay with less than 210deg and wider than 113lsa. lift? choose whatever you want (or your valve train can cope with.

[Stav]

Thanks man ..I am hoping the edit and hi stall may be able to cope with something a tad larger. What problems occur if we go bigger?

[Stav]

Not a worry.Ill find out soon enough.There are 3 cams in the garage getting ready for testing...chances are that the dev 4 is the best one.356 to 400nm on a recent dyno day shows its a good little unit.