I'm putting in the zz4 cam in my stock lg4 and was wondering if I NEED to replace the springs. If I can keep the ones I have I'd rather do that cause I'm saving up for some new heads. What's the effect of leaving them on there?

 

That is a huge cam for a 305 and YES you need to replace your springs. Your old ones are worn and will not support the added RPM's and stress of the new cam. Your heads will NOT even support that cam. I am pretty sure that cam is over .480" lift with 1.5 rr's which is way higher than the stock heads can handle.

 

So I need completely new heads too? I don't understand why that would be.

 

The stock heads are machined to allow your valvetrain to accept no more than .480" lift. The cam that you want is over .480" on its max lift therefore exceeding the amount the stock heads are designed for. The same goes for moost other GM heads. That is why you read that people get the vortec heads machined so that they can use a bigger cam, one with more than .480" lift. Does that make sense.

 

What would happen if I kept the stock heads and valve springs? I know there are people that have used big cams and stock heads so there has to be a way. I need to know what I can do because my car is apart and the cam will be here wednesday.

 

You need to check for clearance on you valveguide bosses, they may need to be machined (requires removing head and taking to the machine shop) so when the valve opens at lift, the retainers/keepers don't smack the bosses.

If you do have clearance, and can leave the heads on, it's a given you'll need new springs, or expect some valve float way before you reach shiftpoint.

 

if you ran the cam with the stock heads, you would barely use the full potential of the cam, it would be like making a 406 and putting stock tpi on it, you will chooke the life out of the cam.

The reason being because the stock heads simply do not flow well at those high lift numbers.

 

also at the lift that cam has, you are surely going to pull the rocker studs. i know people who have pulled studs at alot less lift than that.

 

Find part# 264HP on this page

http://www.competitionproducts.com/page51.html

Would have been a better choice for a stock LG4

At minium I'd get some hi perf replacement stock diameter
valve springs like Comps 981 or cranes 99848
or competition products #98214
http://www.competitionproducts.com/page32.html

Hyd roller cams generely lift the valve faster, they need more spring pressure to control the valve train.

Valve float is the problem you'll get if you don't have the right valve springs for the job.

 

What exactly is valve float?

 

take me for example, john. the lg4 in my z28 pulled a stud with the stock flat tappet cam.

 

yeah, and paul pulled 3 studs on his 416's at .470 lift.

 

Well, so far I havent pulled any studs with my xe268 which has .480 lift. Not to say that I wont, but I plan to start porting my sportsman II's soon, and they have screw in studs w/ guide plates. I am currently running a set of ported 416' on a 350 with stock studs, but I do have the proper springs. I have beat a LS1 and a decently modded LT1.