(Possibly) stupid question, about swapping cams

[Guest bastaad525]

Just wondering... I know MSA nearly insists that you don't change cams without changing everything else i.e. valve springs, rocker arms and lash pads. However, a mechanic friend of mine who does nothing but Z's says he's done quite a few cam swaps with mild to wild cams, WITHOUT changing anything else on the head, and that he's never had a customer complain about it (he's been working on Z's for 16 years). I'm wondering, if I go with a mild cam, with .450-.460 lift, and .270-.280 duration, do I need to change all that stuff??? It get's pretty expensive... Anyways I'll probably do the rocker arms if anything, however I've also heard that the rockers MSA sells aren't that good of quality and to buy Nissan only. Is this so? That adds quite a bit to the cost too Has anyone here changed cams WITHOUT changing the rockers? Did it work out okay? I know I'll need new lash pads just to make up for the larger lift of the lobes, that's a given, but what about valve springs? Can I keep my stock springs with the .450-.460 lift?

[johnc]

Have your mechanic friend do the work and provide a warranty. Normally, I'll replace most of the stuff mentioned unless I know how many miles are on the parts and how they were used.

[RedNeckZ]

Only with the high revving engines do you really need to change every thing. It mostly depends on the RPM, you will be running. If you stay below 7000 rpm you shouldn't need to change that much. With a new cam you will need to put all new rocker arms in at least. I didn't do that and messed up the same cam, you are looking at to put in. But you can do with the stock springs and lash pads. Always replace the cam and rocker arms together. I was told that the arms sold by MSA were not that good. Well I have almost 7000 miles on them and haven't any problems yet. I have used the cam you are looking at on three Z's now and like it a lot for the street. Also run three 45 DCOE's on them to. Like the combo over all. Good luck with the cam. Rich.

[DAW]

Regarding the valve springs, I've looked at the specs for springs on the L4/L6, VG30, and Z series 4cyls (Z20/22/24). The inner springs are about equal on L and VG30s, and stronger than Z series. The outer springs are strongest on VG30, then Z series, then L series, then the L24 Maxima (intakes). Some specs for outer valve springs:

 

Spring test Assembled ht.

L4/6 108lbs@1.161" 1.575"@21.3lbs

Z 4cyl 115.5lbs@1.18" 1.575"@23.0lbs

VG30 117.7lbs@1.18" 1.575"@25.5lbs

LD28 115.3lbs@1.18" 1.575"@23.0lbs

L24Max 105.2lbs@1.18" 1.575"@?

 

Assuming the springs are the same diameters and interchangeable, you may be able to exchange your outer valve springs for some from either a VG30 or a Z20/22/24 to use with your moderate cam and not have to buy an aftermarket set of springs. Has anyone else tried this? DAW

[Guest bastaad525]

Actually the only place I ever heard that the MSA rockers are not that good was on Bryan Little's website. Apparently he purchased some of these rockers. Actually if I remember correctly, he didn't purchase them from MSA. Anyways, the brand of the rockers was Sealed Power, and he said that they lasted about two years before developing major problems from scoring and pitting on the wipe surfaces. Anyhow, he was later told by someone who works at MSA that the brand THEY sell is also the Sealed Power brand, not the Nissan brand as their catalog claims. So that is why I was wondering about their rockers... personally I've never known anyone who has installed rockers from MSA... and unfortunately RedneckZ's example isn't a good one since they're only 7000 miles on them. Anyone else use MSA rockers for more than a couple years with no problems?

[Guest bastaad525]

By the way... Redneck you said all you changed were the rockers, does this mean I do not need to change from the stock lash pads?

[Lockjaw]

The only time you should worry about swapping springs is when the cam lift is over .460 since that is when coil bind sets in, although I have run higher lift cams without problems.

 

I have also swapped cams without swapping rockers, although I did swap lash pads to make the geometry work out.

 

I suspect the main reason to swap is the wear patterns from a different cam cause more valvetrain noise when used on another camshaft.

 

You have to run different retainers if you use more than a .160 lash pad as the stock retainers have problems holding them in place.

[Guest bastaad525]

See that makes more sense to me, to have to change the lash pads, but for rockers I dunno. I would think that it wouldn't matter unless the rockers I have are worn oddly. If there is a nice even wear to them, it doesn't make sense that they would 'destroy a new cam instantly' as MSA puts it. The other thing that makes me think this, is that, when I bought the head used I took it to a machine shop to get a valve job, and the cam and rockers and all that were off the head when I got it. The machine shop didn't do anything to the rockers or cam except install them when the headwork was done. So of course he just put the rockers back on in a random order, so they wouldn't have been matched up to their respective cam lobes. Yet, I've put 25k miles on that head and haven't noticed any adverse effects from this. Anyone else change cams WITHOUT changing rockers??

[Guest bastaad525]

By the way, quick q: What size lash pads would/should I need if I go to a .450 or a .460 lift cam? If everything else else is pretty much stock spec, meaning no shimming on the cam towers or different valvestem lengths or anything like that.

[yo2001]

stock lash is 3mm which is like .120". My .488" lift cam uses .160" lash pads so I would think it should be in .140" range. Make sure the rockers are in good shape. Also, balancing the rockers while you have them off would be a positive thing.