Thread: The real deal with a big cam!?

I have a build thread for this Impala http://www.grandprixforums.net/threa...-SS-quot-build

The plan at first was XP/105's etc.

That changed to XPZ/130's/double roller chain

Cliffs on the engine build for those who havent read the build thread...
diamond +.020 9.5:1
ported heads
ARP everything
E85
Phenolic full size IC
Gen V/ 2.7" pulley + 5% OD

Now I have a recent influx of cash put down to move forward with the project and the time has come to order the cam. We were pretty final on putting a XPZ in it but after reading about valve guide failures and complications with valvetrain geometry at high lift it has me wondering.... Is it really worth it to put a XPZ in a street car? Will it EVER be reliable enough to drive 1000 miles out of state with a big cam? How much power will an XPZ or IS3 really make over something much simpler like a XP? The owner isnt 100% automotive competent, if he has issues and the timing cover or heads have to come off he will be stuck trying to find a shop that is competent enough to understand the setup and that is willing to deal with it.

Also IF we do go with a big cam which one is actually the best choice for this setup? I have read through ZZP's not-so-technical info about the XPZ, many threads on 3800Pro regarding XPZ vs. IS3 and Intense racings own IS3 Vs. XPZ write up (http://www.intense-racing.com/cam_comp/index.html.) Another thing that has me questioning all that I know is that ZZP claims they made 464hp with a XPZ. Intense racings own test data shows just under 400 for both cams even with a M112 on the motor! They also show with a M90 they only made 340 whp with a IS3 and CNC heads? A funny thing about their data is that the XPZ setup they tested made 5 less HP but made +10 ft-lbs which they dont mention in their take on the numbers. That sounds like a fair trade off to me and is still swinging me towards a XPZ. We were thinking we would like to potentially make as close to 400whp as possible with a genV M90 but that is looking pretty IMpossible at that rate.

I daily'd an xpz for quite a while. If you are doing heads, I'd definitely recommend an XPZ.

Originally Posted by GTPpower

I daily'd an xpz for quite a while. If you are doing heads, I'd definitely recommend an XPZ.

What did you run for rockers and lifters? How did you shim them to correct the geometry? Did you go through the whole deal of measuring the pushrod length and shimming or did you just bolt it together with the zzp pushrods and shims and run it? Did you run stock valves?

I am pretty set on a xpz but I don't want to mess something up in setting it up and cause problems. What happened to your XPZ setup? Why are you not still DDing it?

Originally Posted by Anthony Smith

What did you run for rockers and lifters? How did you shim them to correct the geometry? Did you go through the whole deal of measuring the pushrod length and shimming or did you just bolt it together with the zzp pushrods and shims and run it? Did you run stock valves?

I am pretty set on a xpz but I don't want to mess something up in setting it up and cause problems. What happened to your XPZ setup? Why are you not still DDing it?

I ran stock L26 rockers, lifters, and valves. I didn't need to shim the rockers. It's a good idea to measure your pushrod length....the standard pushrods that zzp's sells with the XPZ are what I needed, so I lucked out. But, you should still invest in a pushrod length checker. They are cheap. Unless you are running different than stock valves, you probably won't need to worry about shimming the rockers.

I didn't have use for the car anymore, so I sold it. But, the guy I sold it to still DD's it. It was a fun car. Only thing I didn't really like about it, was the vibration that the double roller caused.