Valve Spring Shims

[NC280z]

Does anyone know the correct dimensions (inner/outer diameter) for valve spring shims for the L-series motors? I've found that the installed height on my Schneider springs are far too high, preventing me from being able to properly set the lash. I know that Crane, among others sells shims, but most seem to be for small-block applications. I'll probably need shims in .020 or .030 measurements, if someone knows a good brand to go with I'd appreciate it. Thanks.

[datzenmike]

Shims won't help. The valve spring length has nothing to do with how high or low your valve tip sits. Your valve is tight against the seat, the only thing between it and the rocker arm is the lash pad. 

[NC280z]

Shims are used to correct for excessive installed height of valve springs, per the "How to modify" and "How to rebuild" books, and according to nearly every machine shop I've talked to. It's done on Datsuns, and on most anything with an overhead valve design. You are correct on the valve springs not affecting the height, it's the retainer design, valve seat, keeper location, valve stem length/keeper cut location, and the spring seat that determine installed height. The cylinder head I have has had a valve job done to it, so I need to install more shim(s) at the base of the spring to compress it to make up for the material that was removed. If the installed height were too short, the spring base (inner and outer) would have to be machined to allow the spring to extend further. 

 

The Schneider retainers have a higher install height than stock (.030") so I've ordered stock retainers/ springs to match the stock cam I've got in the head. The other problem was that the stock lash pads sit too low in the Schneider retainers, further complicating things. Chances are that I'll still need shims, and unfortunately the Modify and Rebuild books (and the FSM) don't cite sources for shims, or their diameters inside and outside. I could take the stock shim to the machine shop and match it, but I was just wanting to see if anyone else has found a reliable source and size for shims.

[datzenmike]

 I've found that the installed height on my Schneider springs are far too high, preventing me from being able to properly set the lash. I

 

I must be missing something. 

 

Slipping shims under the spring will only compress the spring it won't change the height of the valve tip where the lash pad is, and this is what the rocker rides on. 

 

If you don't have room to set the lash, perhaps the seats were set too low into the head. This would 'raise' the tip of the valve, the lash pad and the rocker arm too close to the cam.

[NC280z]

I see what youre saying now. The shims won't drop the retainer lower, they'd just compress the spring. I hope the stock retainers work out for me, otherwise I'm going to have to remove the head to get the seats checked.

[datzenmike]

The retainers are held on by the two keys or collets that grip the valve stem, and again, the rocker does not rest on them, it rests on the lash pad and it, on the top of the valve stem.

[NC280z]

Yes I know where the rocker rests, but the contact issue I'm having is between the rocker(s) and the retainer(s), because the retainer is a different size than stock to allow larger lash pads and a wider spring, and possibly because the valve stem height is too tall due to the machine shop grinding too much seat material away. The valve stem would then extend further towards the cam, and with it the retainer causing my interference issue. I incorrectly believed that shims would correct the rocker/retainer issue, but it would only affect the springs height.

 

I'm expecting to have to remove the head and have the seats redone, what's a typical price range for work like this?

[Sealik]

Thought you were going to use stock retainers?

[datzenmike]

You can replace the stock springs/retainers without removing the head and try them. If still not adjustable then the valves have sunken into the head and will need refreshing.

[NC280z]

I've got an air compressor tool on-hand as well as the spring compressor. I'll change one spring/shim and see if I can get by or if I have to remove the head. Fingers crossed for getting by w/o head removal.

[datzenmike]

Don't use a compressor, there's risk of failure and that valve will drop into the cylinder. Take the plug out and shove a few feet of ripe in the cylinder. Tie a not on the end so you don't loose it. Crank the motor over with a wrench towards TDC compression stroke and the rope will hold the valve closed. You could come back next year and nothing changes or do this on the side of the road.

[banzai510(hainz)]

what size lash pad you have in there?

so you need smaller. the smallest I think is .150 if avail.

 

what I did on the engine I was buiding is the lash pads were also to big I needed smaller on my Schneider. I got a regrind and used my taller pads I had.

the Scneider I used in another motor which worked out fine.

 

stock pads are counter sunk on back and are about .118 if I remember right... Schneider gives about a 160 in the kit.

[scooter]

If i saw this earlier i wouldof had your answer, so the best i can tell ya is go to a machine shop and theyll be able to match them up in ya, from .015 to .060 shims. Dont be scared to stack them unless there is no boss left to keep the shims and spring centered.