I would like to know if there are any gotchas with installing a ZZ4 cam and springs into a newly rebuilt L98 with 083 heads. These are my concerns:

1) Want to do minimal head machining.

2) Want to retain the stock intake and egr.

3) I have heard about retainer/guide interferance.

4) Dont want to install studs and guides.

Are the ZZ4's the same diameter as the L98's springs?

Are there retainers that I can use so that the guide tops won't have to be machined.

Thanks....

 

the zz4 springs are the lt4 springs. i just got through putting lt1 springs on mine. i had to cut the pockets to 1.46" diameter to fit. also, the springs ended up at 1.800" intake side and 1.900" exhaust with a .060" shim under the exhaust ones installed height. my next move is to the zz4 cam. i will be going to screw in studs and guideplates. with 1.6 rockers it puts the lift to .505/.544 the pushrods will probably hit the heads at the stud side. so, i'm not taking the chance. also, do yourself a favor, put viton seals in. i had umbrella seals installed and all of them pulled up. so everytime i accelerate, i get a big cloud of smoke. and 1 quart of oil in 175 miles.

http://www.fl-thirdgen.org/mrr23-3.html

 

hey mrr23, i put viton seals on the intake and umbrellas on my exhaust, do you think i should have done viton on exhaust too?

for the zz4 cam, you will HAVE to get screw in studs, wider spring pockets with those springs and also have the tops of your guides milled.

 

intake side should be fine. that's the side that sucks inward. the exhaust would blow outward up the guide. so it would look like blow by. but it wouldn't have hurt to have done them all.

 

I've not seen those heads, but I suspect you may have some guide interference with 0.474/0.510" lifts. You'll certainly need better springs. The GMPP LT4 springs are adequate, but would require spring pcoket machining. Without a doubt, you'll need screwed or pinned studs, and if you are going through the effort, you might juat as well thread them rather than drill and pin them.

Whatever you decide, get rid of the stock retainers and get the LT4 retainers and locks at a minimum, or lightweight Comp parts.

You'll probably also have to check push rod clearance very closely.

And as if that weren't enough, your stock rockers are going to be disappointing with that cam - if they survive long at all. On the "up" side, maybe the stock rockers will flex enough to prevent guide interference. (I know, that wasn't really that funny, just true.)

 

what do you think about these rockers? they're stamped chromemoly but are they any better than stock, strength wise? http://store.summitracing.com/partdetail.asp?part=9399

why do you need to change the stock retainers? do they deflect from the higher spring pressure?

 

Stock retainers?

First, they're too heavy.

Second, the exhaust retainers are designed for valve rotators (Yuck! More mass...)

Next, stock retainers use 7° locks (keys). Titanium retainers use 10° locks for better stress dispersion with the stiffer springs.

HINT: GMPP LT4 retainers are titanium alloy. (How do I know for sure? I used to work in the plant that made them for CPC and Cadillac, and it isn't a GM plant.)

Finally, the fit of the stock retainers to the larger diameter springs isn't going to be ideal.