I have searched but get oddball posts about it and then I get lost.

What are the things I need to do and get for a ZZ4 Cam install on a 1987 L98

1. Got the Cam
2. ?????
ect....

Thanks!

 

I'm not an expert but you might want to buy a new set of valve springs. I don't think the stock head springs can handle the ZZ4 lift.

 

True - the stock springs aren't stiff enough to handle the ZZ4 lift.

 

So New springs... can anyone throw a list together or find a kit. It would make it a little easier. I've searched but nothing.

Can you keep stock rockers?? but just get new springs...

 

As long as they are in good shape, you should be able to keep your stock rocker arms. Or you can upgrade them to a roller or roller-tip setup. A higher-ratio roller/roller-tip would increase your valve lift and make that ZZ4 act slightly bigger.

Personally, I went with Comp Cams Magnum roller-tip rockers on my Dart heads.

 

that cam aint too big so you probly could get away with your stock rocker arms. it be best to upgrade to a roller tip just to beef up the valvetrain and make it more efficient.

this is the ZZ4 crate motor valve spring from GMpartsdirect
p/n 12551483
retainer P/N 10168424.
http://www.gmpartsdirect.com/perform...CATID=734.html

101# @ 1.78" installed height
332 lbs per inch averate rate

you probly could get away with comp 981 springs in the 1.25 inch diameter. they have higher average rate of 417lb/inch tho but have 1.7inch installed height pressure of 105lbs.
with 1.5 rockers you need to support .520" of lift, and add clearance so you should allow for atleast .550 lift springs. not sure of the lift on the 981 springs.

 

So I don't need to machine the head for clearance for the springs?

 

yes get the valve guide bosses machined down. they should bottom out on the retainer at .480 lift or so.

OR without machining...only other option is to get .050 offset locks and shim the springs up .050" as well. this will give you .050 inches of clearance while retaining stock install height and pressures. .480 + .050 = .530" so your covered to about that. But do allow for safety clearance. I wouldnt go more than .510-.520" on that setup. ZZ4 would be cutting it close so you'll have to check for clearance between the valve guide boss and the retainer still. tough call on this setup. have to stick with 1.5 rockers tho

it be best to just cut the guides down. This is what i plan to do, i think lol

as far as springs, i'm not sure if the stock spring pocket will accept larger diameter springs over 1.25 inches. else you'll have to get those widened

 

Would that zz4 cam work on the alum vette heads? casting 113's. Or do they as well need to be machined down to allow for the extra lift?

 

Anthony, that's the cam that I pulled out of the motor. The heads are perfectly matched to the ZZ4 cam.

 

The ZZ4 heads are the exact same as the L98 Corvette heads, except the ZZ4 heads have better springs (the LT4 springs).

For a .500" lift cam on stock iron L98 heads, get yourself the Manley 22410-16 springs, the Manley 23652-16 +.050" steel retainers, and dont forget the stock replacement valve stem seals so you dont get the "puff of smoke" at startup.

 

Found out today that I work with a guy that his family owns an engine machine shop. He said this weekend wel can go machine the heads and he'll let me watch how they do it. Best of all Free of charge, just a case of beer! So instead of buying the retainers for $70 I can just have it machined down right?? The guy knew exactly what I was talking about (having the valve boses) machined down. What would I need them machined down to so I have clearance for the ZZ4 cam??? He also said he could tap for screw-in studs. What would you all do??

 

would that be suitable for a hydraulic roller with 220/230 duration and .510 lift? seat pressure is 130 at 1.75" installed height and 320 open at 1.200". that seems like enough pressure for hydraulic roller as comp recommmends the 1.43" OD double springs that have a seat of 132 and open of something over 300lbs, i forget the specs.

reason i ask is that stock heads accept 1.25 inch springs and i dont really want to have the pockets opened up

 

ah ok, thats what i thought. So if the vette heads are the same as zz4 heads then why are people saying i/we need to upgrade the rocker studs and springs? shouldnt they already beable to suit the lift requirments of the cam?

 

I am running the Manley 22410 with my LT4 HOT cam, with 1.65 rockers on the intake and 1.6 on the exhaust. That's .541/.525 lift, with no problems. That spring/retainer combo is good for .550 lift.

The reason to upgrade the rocker studs is because the stock studs are pressed in, and with a higher lift camshaft and higher pressure springs, one of the rocker studs could pull out and cause damage to your valvetrain.

I *THINK* the ZZ4/L98 heads already have screw-in studs, but I know the L98 iron heads do not.

 

ok that makes sense, i will find out when i get the heads, but it just seemed wierd that i would have to upgrade the heads that were already built up for the zz4 cam.

 

Nascar, those heads were built with the zz4 cam in mind. If you go to a more radical cam, it is always a good idea to make sure the valvetrain can handle it. The zz4 cam is on the mild side of the power spectrum. Not that good power cannot be make with this cam, it's just a smaller all around cam than what most performance oriented combos are utilizing. Don't forget to do your research so that you can do it once and do it right. Please let me know when you get the heads!

Will