I have a ZZ4 crate motor that was rebuilt with a CompCams Camshaft 218/224 duration and .495"/.503" lift with 1.5 rockers. Now the ZZ4 comes with LT4 springs which are supposed to be good for lifts up to .525". I am running 1.6 rockers so that puts my lift up to .537" on the exhaust. This troubles me because I spent a good bit of money on this motor and don't feel like trashing it because of inadequate springs.

I know that the LT4 springs are 1.34" in diameter and none of the aftermarket springs I have seen use this same diameter, they are all larger. So are my spring pockets machined to only accept a valve spring with a 1.34" diameter? If I need a bigger diameter is my only option to remove the heads and have them machined. The motor is all built and ready to go so if disassemly is necessary for me to change springs then I guess my only other option is to scrap the 1.6 rockers and put on 1.5's, so that should put my lift well within the limits of the LT4 springs.

Any advise on this would be appreciated.

 

I'm not familiar with the LT-4 springs myself but most stock high performance springs will not take that much lift. I'd check further on that.

Also, ZZ4 heads themselves are just old L-98 aluminum 'Vette heads and they will not take that much lift, stock. I had a set, brand new in box in my basement and the retainers would hit the valve guide seals at only about .480" lift.

I recall that the spring pockets were pretty well maxed out with the springs they came with. I think having the spring poskets machined for larger springs would be mandatory if you go any larger in diameter.

So that means machine work to mill down the guides and enlarge the spring poskets.

Or.... you might look into installing valves with longer stems by abut .100" and then getting springs (same diameter or smaller- 1.25" is very common) designed for a taller ~1.850" installed height versus the stock valve length spring install height of ~1.750". Equivalently longer pushrods would be required if you choose to go this route to keep valvetrain geomentry correct.

No easy fix here, I don't think.

 

Thanks for the reply,

Let me chime back in with what limited knowledge I do have. Although the L98 aluminum head and the ZZ4 heads share the same casting, the ZZ4 heads were upgraded with LT4 springs. Those springs are 1.34" in diameter versus the stock L98 aluminum head spring which is 1.25" diameter. So I am pretty sure that the spring pocket has to be machined to the diameter of the valve spring, which makes me think that GM machined the spring pockets of the heads that were going to be put on the ZZ4 crate engines.

Now I have never seen another spring besides the LT4 spring that is 1.34" in diameter, so if you ever wanted to change springs on a ZZ4 you automaticaly have to get machine work done to the spring pockets? Well the whole thing is put together and is ready drop in so there is no way I'm going to pull all that stuff off to get bigger springs put in. The end solution is simple, but will end up costing me an extra $300. If I buy some 1.5 ratio rockers then my lift is well within the limits of these LT4 springs. The hot cam is .525 and the ZZ4 has an exhaust lift of .510 so with the 1.5 rockers my max lift will be .503.

Anyway this just sucks that the engine builder decided not to replace the springs with some bigger better ones, which would let me keep my 1.6 rockers and have peace of mind at the same time. Oh well I'll know better for the next build.

 

A lot of the LT1 guys use Crane valve spring kit 10308. It fits the LT1 spring pockets without maching and is supposed to handle .600" lift. I'm almost sure the spring pockets are the same diameter as the ZZ4 heads since LT4 springs will work in either head with no machining.

 

Thanks for the reply. I looked up those springs you talked about, and it shows they are 1.255" diameter.

What really confuses me is, since my springs are 1.34" diameter is it alright to go down to a smaller diameter spring? Is it going to move around in the pocket? Is machining only necessary when going to a larger diameter spring? By all means I would love to keep my 1.6 roller rockers but having machine work done at this point in time is out of the question. So its either find a spring that can handle .537" lift safely and that will fit correctly into the ZZ4 heads spring pockets or buy new 1.5 roller rockers and just use the LT4 springs.

 

If you run smaller springs, you'll probably need new retainers too. But like Damon mentioned, even if the spring can handle the lift, the heads may not. I'm running .517 on the exhaust side on some L98 vette heads, and the heads havent been machined for clearance. Valves and retainers are stock. I have about another .020 I could go before I would run into problems, but thats running the absolute minimum on clearance. But you MUST check it, otherwise you could have some serious problems. The clearance can and will vary from head to head.

IIRC, a 1.44 spring will not fit without machine work.

 

Well I decided that for me to keep the 1.6 roller rockers is just going to be to much trouble without maching the heads. I think the best thing for me to do is just buy some 1.5 roller rockers and be done with it. Then I only have .495/.503 lifts which should be well within the limits of the LT4 springs.

So since I am going to go that route and just use 1.5 rockers is there anything I need to watch out for as far as clearances go?

Thanks