ZCar Forum banner


250 Views 2 Replies 2 Participants Last post by  blue
I'm following your recommendation:

"N42 head (no shaving) with a flat top piston and a 270/270 cam with a header"

I have a couple of questions:

- What lift would you recommend?

- What are your thoughts on asymetrical grinds? Frank from "How to Modify..." fame recommends this

I plan to follow your advice on Delta Cams grind, rocker re-grind, Summit's Crane springs and retainers. Also Si Valves.

btw anyone have a set of 12 rockers forsale?
Not open for further replies.
1 - 3 of 3 Posts
The max lift is dependant on the duration. It is not a good idea to have super fast ramps on a street cam. It is possible to grind in 0.500" on a 270 degree cam but the springs would need to be very strong and the cam would wear out very quickly. If you ask delta for a 270/270 cam then the lift will be pretty much determined by them. However, it should be around 0.0450" to 0.0475". To get 0.500" lift and keep the cam ramps reasonable then a 290 degree cam would be required.

Typically asymetrical grinds are used to correct for a problem. For example, more exhaust duration are used when:
1. the head doesn't flow well on the exhaust side (E/I less than 0.7),
2. if a stock exhaust manifold is used
3. in a automatic car
4. when a small engine is in a big car
5. blowers, superchargers, and n20 (not turbos)

For a Z, it is not a bad idea to give a little more exhaust duration. I believe delta has a 274/278 grind with 0.480" which I have personally installed and driven in a friends car. It took 0.180" lash pads to correct the valve geometry. It ran very nice, mild lope at 1000rpm, and had power from 2500 to 6500.

Don't forget to buy a "head on block" Nissan spring compressor tool! And you will need a good sized air compressor to pressurize the cylinder to hold the valve up while you change the springs.
See less See more
Thanks again!

I am very grateful!

I'll keep you posted.
1 - 3 of 3 Posts
Not open for further replies.