blind_96

I have a tech question involving rocker arm shims and guides for the SR20. The head that they are in has had a valve job done to it and larger cams installed (264 and 276). Now I want to re shim it. I know that some people say there is no need because the oil lifters will make up the difference, but I want this thing right. The issue in question is this: how thin can these shims be thrimed to without breaking under load? If anyone has any ideas or tips let me know. thanks

Epstein

There are a hundred variables here. What you need to do is get/build a tip height gauge. Put on a guide and measure the height. Then obtain/grind a shim to match the height on the other valve. You're just trying to make them the same height. The actual height number and difference from cylinder to cylinder doesn't matter. Now the rocker will sit flat/square to the cam lobe. The rocker to cam clearance will set itself automatically when the HLA pumps up.

I think Nissan will sell you shims down to 2.0mm. It's been a while. I've lapped them with sandpaper without an issue as well.

blind_96

Unfortunatly nissan will only sell 2.7mm. Mabye I am missunderstanding the HLAs. When I place the cams in they touch the rocker arms. The book it this point requires there be a clearance of ... like .03mm... or something. But since the valves were done the gap between the cam and it correct location appears to be drastic. Right now my shims are reading 3.02mm. If I were to grind these down to say a 2.6mm ( or just buy 1 set) will the HLA still give me the .03 gap that is called for. Am I understanding the HLAs right? Can I bottom out the HLAs to where they won't function propperly?

Epstein

Yeah, with everything in and the HLA fully compressed, there needs to be some gap between the rocker and cam. But make double sure the HLA is fully compressed before making this determination and screwing with everything. The HLA will always work no matter what height, as long as it's not bottomed out. In a regular cam swap, it's normal to have it all really tight because the HLA's are still up and not compressed. You probably already know this, but during operation there is zero gap between cam and rocker.

Ahh, 2.7mm is probably the smallest from Nissan. Tomei will sell you thinner ones as well. Just grind them down to whatever you want.

Z28ricer

There was a company a while back selling a height tool, for under $200, you can probably find the place on freshalloy or something, I tried getting ahold of them a while back to buy one, but didnt get anywhere with it.

The tool from kent-moore or whoever supplies the stealerships wants something around $500 for it, IMO total waste, of course if I was staying SR i'd be solids every day of the week anyway.

Alternatively you *should* be able to use a set of solids, just use them to take your measurements and get things right.

blind_96

OK, makes sense now. Here's what I'll do. Take the HLAs out, drain the oil out of them so they sit as low as possible, put everything back together, check my clearances. Right? Hopefully there will be a minimal grinding to be done. Is there a point that the shims will break or cause problems because they are too thin?

Z28ricer

I'd just get a set of stock HLA's from junkyard, stick some washers inside as shims to make them solid but proper height, then figure out what shims you need from there.


What is making you think you'll need thinner shims than are available, did you only do half a valvejob or get shorter / longer valves and only do a half a set ?

Epstein

I've run shims down in the 2.4-2.5mm range before and never had a problem at 9k+ rpms.

Compress the HLAs fully, throw in the stock guides and shims, bolt in cams, then make sure there's some clearance between rocker and cam. Once you've determined that there is clearance (and that the head place didn't screw it up), remove the cams/lifters/rockers and start grinding your shims to be even with the guides. Do a search on Freshalloy for instructions to make a tip height gauge.

blind_96

Where are you from that there are sr20s in junk yards? SERs maybe?
The head has had a five angle valve job done on it and we are using bigger cams than what we had in there. I don't know for sure what size we need, it just looks like a big gap. I only want to do this one time, so I want to have all the information first.

Z28ricer

SER's and G20s plenty, same shims, same lifters.

Bigger cams, valve job etc, the guides themselves are only one thickness (3.0mm ?), the shim is to just level the rocker itself, I just dont see you ending up THAT far off, but I suppose its possible.


Epstein: What was it that had you ending up with shims that thin ? Was it something of an oddball setup ? Guides machined thinner ?