88gta_hiflyer

iTrader: (1)

I'm about to tear into my LB9 to address a lifter problem and figure while I'm replacing lifters anyway it might be a good time for a cam swap. I picked up a ZZ4 cam and valve springs super cheap here locally so I'd like to use it. Who has done this cam swap before and what were your results? I've done lots of searching on here and found numerous posts on this topic but haven't seen much about the actual results from members who have done it.

Also, there are lots of conflicting accounts on here about what all needs to be done to run this cam. I'm thinking vavle springs should be the only change I need to make. Can anyone confirm whether or not the ZZ4 springs will work on my stock LB9 heads? Some claim machining is needed while others say they're a drop in fit, so which is it? Thanks in advance.

88gta_hiflyer

iTrader: (1)

Anybody got any experience with this cam?

Orr89RocZ

iTrader: (20)

I dont think the ZZ4 springs would fit, they are the 1.32" Lt4 springs which I think are too wide for stock valve pockets. I dont think stock heads can fit more than 1.26-1.28" as they sit.

Popular upgrade is either 918 beehives which SHOULD beable to handle zz4 lift on stock head without machining but I'd still have them machined since studs are press fit and you should have screw in or pinned rocker studs.

OR the manley 22410's are nice. If you use offset retainer and .030-.050 worth of shims underneath, you should beable to hit .525" lift or close to it without machining the heads. Once again, its a good idea to do it anyway to make sure you dont pull the studs out.

88gta_hiflyer

iTrader: (1)

Thanks for the reply. What basic specs should I be looking for in a valve spring for this cam with stock heads? Both of the spring sets you suggested look nice but they're a bit more than I'd like to pay for valve springs. I guess I don't really know what to look for other than the outer diameter of the spring. How do I figure out how much lift they will handle?

Dyno Don

iTrader: (7)

Those stock heads won't take more than .460 lift, the retainer will hit the valve seal.

You must machine the heads to use that cam.

Orr89RocZ

iTrader: (20)

Machine the heads first to handle any spring you want to put in the head, then you can use the ZZ4/LT4 springs with this cam just fine. Thats a good bet. Machine work to do this shouldnt be more than 200 bucks.

88gta_hiflyer

iTrader: (1)

So basically there is no magic combination of springs, shims, retainers, offset locks, etc. that will allow me to run this cam without machine work on the heads? Just want to make sure I'm understanding correctly.

Orr89RocZ

iTrader: (20)

Well there is, according to some here. I have not done it but its supposively possible.

If you ran .050" shims with .050" offset locks or retainers, then the entire assembly sits .050" above the valve guide boss. Since stock heads usually bottom out the retainer on the guide boss at .460-.470" lift, adding .050" gets you to .510"-.520" with no margin for error.

Others have reported higher available. Its something you will have to measure on your heads. take out the spring and measure installed height with valve spring micrometer. Then you need to setup some kind of light checker spring to keep valve closed, put a dial indicator on valve tip on the retainer, and push spring down to open valve until retainer hits valve guide boss. Measure the lift to do that and you have an idea what margin you have available to work with.

918 beehives apparently work in a similar way. The shape of the spring uses a smaller diameter and thinner retainer so there is abit more margin for lift before hitting retainer on guide boss. Guys have done this with .492" lift hotcams with success.

88gta_hiflyer

iTrader: (1)

Well I'm by no means an engine builder but your numbers make sense. As many threads as there are about putting zz4 cams in LB9's I'm sure someone has done it. I'm just trying to figure out as much as possible before I tear into the project because I'm going to want to move quickly once I'm in there. I'd like to have all the right parts before I get started if possible.

So for clarification, are you saying that Comps 918 beehive springs are basically the same as using .050" shims and .050" offset retainers due to their shape? So if I use the 918's I shouldn't have to use any shims or offsets at all right? Thanks for your help.

Burnout91

When I installed the ZZ4 cam, with the valve springs from the ZZ4 motor, in a stock iron-headed L98, what I found was that it was actually the lower edge of the valve lock that was contacting the the valve guide. I trimmed the lower edge of all the valve locks (don't remember exactly how much, probably ~.030" - .050") to get clearance, and fully deburred the trimmed area. Then I ran the engine for years with no problems. Later sold the heads to someone who was also running the ZZ4 cam in an L98-based motor, and haven't heard of any problems from the new owner of the heads.

Tolerance build-up will cause the clearances measured to vary slightly from engine to engine, so like was said, take some measurements from your engine to determine how much additional clearance is required, then decide how you are going to achieve that clearance.
Bill

88gta_hiflyer

iTrader: (1)

Thanks for the reply burnout91. So did the zz4 springs fit into the pockets of your stock heads without and modification. That was my main concern with those springs but I'd rather use them if possible just because they came with the cam so I alreadly have them. Wouldn't .050" offset vavle locks essentially be the same as trimming the bottom edges?

I'm going to have to measure no matter what but like I said I'd prefer to work out as many details as possible before I start taking things apart. Thanks for your input.

Burnout91

No machining was required for the valve springs; offset locks probably would raise the lower edge of the locks. The iron L98 heads may / probably differ from the LB9 heads, so take measurements for comparrison from head to spring.

At the time, the available crate engine was actually the ZZ3, but the cam is the same part for sure, and I think the valve springs are also.

I was unaware of offset locks at the time of cam installation (~'95 - '96...?).

Bill