I just got my engine back from the builder and we installed a Comp Cams .495/.503 lift cam into my ZZ4. Also I had him put on 1.6 roller rockers as well which brings my exhaust lift up to .537 on the exhaust side. He said it would be fine and they weren't binding but I am not sure what the LT4 springs can take that come on the ZZ4 heads. Anyone know what kind of lift this spring is capable of?

 

Depends on assembled height.

 

About .500" max.

I would strongly recommend that you upgrade them; the easiest alternative would be the new conical springs such as from Comp, and the appropriate retainers.

I don't know of any 1.25" diameter springs on this planet that will not cause problems at that kind of lift.

 

Well the LT4 valvesprings bind at .545 lift and the springs good to 535 lift.

Did he happen to machine the heads for that much lift? I can't remember which part has to be machined though. I think it was the valve guides that needed to be machined.

 

I had the heads worked over some. He took a couple thousands off the head to make it straight, then cleaned up the bowl area, 3 angle valve job, gasket matched the intake, and cleaned up the exhaust. After that I have no clue, and thats why I am posting.

The ZZ4 heads come with LT4 springs and they are what come with the LT4 hotcam kit which has a lift of .525 so they have got to be good to at least that, and I don't think they are 1.25" springs either. The place I went to builds engines everyday so I don't think he would leave them in if they couldn't take the lift of my cam. They do check for things like that right?

Does the rpm's have anything to do with coil bind? I have a miniram on this engine, so I am concerned with the higher revs the intake can support.

By the way this engine hasn't been run yet.

 

RPMS have to do with valve float (not enough lifted seat pressure)

 

Genuine GM LT4 valve springs (P/N 12495494) are rated to a working valve lift of 0.525" at an installed height of 1.710". They are 1.434" O.D., not 1¼". They are made of ovated wire to prevent coil interference (bind) at those lifts.

Depending on your installed height, they may be very close to the bind height at 0.537" lifts, adn will certainly run hotter. The springs aren't "all that" and there are better ones available on the aftermarket. That is not to say that all aftermarket springs are better. The K-Martion springs are highly overrated, IMO. Just because they don't break or bind at a certain height doesn't mean they are suitable. Check with Comp on the correct spring.

 

I was under the impression that ZZ4 heads come with 1.25" spring pockets the same as those heads come with when used on a L98, but I could be wrong about that.

The easiest way I know of to screw up an otherwise perfectly good motor is to cheap out on the valve springs. There are very few components that can cause as many problems as they can. They are one of the top causes of mystery lack of high RPM power, from valve float and bounce. They can destroy cams and other valve train parts, and if they break, create some of the most spectacular motor blow-ups there are. If there's any one thing not to cheap out on, considering how little they cost and how much their failure can cost, valve springs would have to be it.

I would not trust GM's valve spring ratings any more than I would trust K-motion's. A number of people on this board have had ugly experiences with the LT4 HOT cam kit ranging from pulled studs to bent push rods to wiped-out cams, directly traceable to overstressed springs. GM has no experience in that business at all, since they've always bought aftermarket for their racing operations; and K-motion won't warranty your cam against lobe failure when used with their springs. Comp, Crane, Lunati, Ultradyne, etc. all will warranty their cams when used with the proper selection of their own springs. What does that tell you?

It is pure folly to try to operate a spring to .010" of its rated coil bind. .050" is even too close for reliability. By that usual standard, as used by all the major cam mfrs., a spring that binds at .545" is usable to a lift of .495".

 

Well that is a big disapointment to hear, I wonder why the builder decided to leave in those valve springs instead of replacing them with the ones recommended on the cam card.

So if I should replace them, I have a question about the springs they recommend with the cam. Are the springs they say to use based on the assumption that it will be used with 1.5 ratio rockers, or do they take into account that people might install the springs and use 1.6 rockers as well?

I have way to much money invested in this engine to take the chance of destroying it with improper springs.

Thanks

 

Generally the catalog listings assume the stock ratio. They never take into account a custom configuration.

Give Comp a call and get their recommendation. You may find you need some machine work to the heads.