Ive removed everything nescessary for my cam swap (305TPI) and i also removed the heads to try my hand at porting them, so my engine is just sitting here waiting for a cam, I have both cams but i cant decide, Its a 97 Lt1 cam if that helps.

Im mostly worried that the Lt1 cam will take away too much bottom end, and/or im worried the zz4 will be to hard to tune (since im hoping to get started in prom burning.)
Also the Lt1 wouldnt really require any modification to the heads, and the zz4 would need the valve pockets machined for bigger springs..
So any advise would be great..
thanks

 

Unles you modify the heads for more lift, the ZZ4 cam will not fit under 083 castings.

Bigger/better springs are always a good idea. Especially when the comparee are the factory springs. At 85 lbs on the seat, they are barely anything to take todays mroe aggressive cam profiles. That and the max out (coil bind) at about .510" lift so new springs would be needed, really, either way you look at it. The LT4 springs are what the ZZ4 engines are equipped with. They are a 1.32" OD. However, I am not a fan of any GM or K-motion spring. Isky and Comp are my personal favorites. Any of the reputable cam companies make a decent spring, though (Crower, Lunati, Crane, etc).

The 986's are a good bet when dealing with factory installed heights. They are a 1.43" OD so machining will be needed. If the heads are going to the shop for seat enlarging, they might as well get worked for more lift (mill the guide boss) and screw in studs/guide plates. With both done, you will be ready for the ZZ4 cam.

And as far as tuning, I'm sure there are people here running the LT4 HOT cam on the TPI with a tune, so the ZZ4 shouldn't all that bad. Actually, come to think of it, it shouldn't be that bad at all.

 

Is getting the valve guides milled absolutely nescessary?
Thanks for the quick reply also

 

Edited the post...

 

Here's the thing: at about .480" of valve lift, the bottom of the valve spring retainer will hit the top of the guide boss, which is obviously cast into the head. This physically halts any further opening of the valve, which then basically puts a holt on the lifter. But since the cam is still rotating, obviously something is going to give, which will probably result in a bent pushrod.