LZ22 head spacer shim?

[toshts]

Currently gathering parts to put together an LZ22 for my 81 720 and I've almost got everything I need. Low mileage stock z22s that's currently in the truck, a complete core l20b with a u67 head from a 620 with mount brackets, intake/exhaust manifolds, carb adapter (keeping the 32/36 for now) and a transmission with the proper front case. Took the head to the machine shop to have gone through (had significant pitting that could have been cracks) and he found it was warped 16 thou and ended up having to take 26 thou off the deck to get it straight, all was good otherwise. Machinist recommended a shim and I was able to find them at 20 thou for the z22/24 (I assume they're like the felpro head gasket one size fits all) and was wondering if I should use one. I've read discussions on decking to increase the compression ratio but I've also read that with this combination the ratio is already quite high and sometimes they take material out of the head to decrease it. The spacers appear to have the same holes as the z head gasket so I would assume I'd need to make the same holes in the spacer as the gasket but would the increased compression or clearance with the decking cause problems/would it be better to run a spacer? 

[banzai510(hainz)]

i figured shop would get datsun cam tower shims. its for timing chain loss when head shaved. You can stack 3 . Shop should know this. Silver seal makes them. Maybe partsgeek.just to let you know sometimes top of head needs cut on L head if cam is binding.

[RLJ]

Warped .016.
Did the machine shop check the top of the head for straightness?

[banzai510(hainz)]

iF cam turns by hand w/o rockers in there i run it.

[toshts]

I'll check when I get off work tonight, I was able to turn it over before machining with a 3/8 ratchet but it felt like it would snap over to the next position pretty hard, not sure if that's normal.

[RLJ]

Were the rockers out when you tried it?

[RLJ]

13 minutes ago, banzai510(hainz) said:

iF cam turns by hand w/o rockers in there i run it.

Agree

[toshts]

1 minute ago, RLJ said:

Were the rockers out when you tried it?

Rockers were in, the head was fully assembled it was right when I pulled it off the block. Didn't ask the machinist whether or not he checked the top but I will

[RLJ]

With rockers in it will do that when turning the cam.
Rockers had to be pulled or loosened completely so all the valves are down below head surface to machine the head surface. 

[toshts]

17 minutes ago, banzai510(hainz) said:

iF cam turns by hand w/o rockers in there i run it.

And just to confirm that's run it with no spacer between the block and head?

[toshts]

2 minutes ago, RLJ said:

With rockers in it will do that when turning the cam.
Rockers had to be pulled or loosened completely so all the valves are down below head surface to machine the head surface. 

Gotcha so pull the rockers and test if the cam spins free?

[ggzilla]

23 hours ago, toshts said:

ended up having to take 26 thou off the deck

...

would the increased compression or clearance with the decking cause problems/would it be better to run a spacer? 

Increased compression is always good. At worst you would use Premium instead of Regular. Premium around here cost 11% more, but you can get some of that back with the increased fuel economy

[datzenmike]

Stock L20B compression.............. 8.4

Stock Z22...................................... 8.42

Above with un-cut L head............ 9.84

L head milled 0.26" 0.66mm...... 10.43

Above with 0.20" 0.5mm shim.... 9.89

 

[toshts]

2 hours ago, datzenmike said:

Stock L20B compression.............. 8.4

Stock Z22...................................... 8.42

Above with un-cut L head............ 9.84

L head milled 0.26" 0.66mm...... 10.43

Above with 0.20" 0.5mm shim.... 9.89

 

Thanks for the numbers, I don't think 10.43 would be too high so I'll probably run it as is after confirming the cam turns by hand with no rockers

[banzai510(hainz)]

if the machine shop bolted the head together and put rockers back in i ASSUME he spun the cam. For straightness up top. To take rockers out u got to put back on block w pistons halfway so when u spin head valves dont hit.. Now i have never used that headsaver headgasket thing. I used cam tower shims. Both is used to keep the chain tite. So if u use cam tower shims u got to take rockers off and towers. I will let others chime on this that know more. Do you trust this shop. If he did lots of datsuns he know about cam tower shims

[toshts]

2 minutes ago, banzai510(hainz) said:

if the machine shop bolted the head together and put rockers back in i ASSUME he spun the cam. For straightness up top. To take rockers out u got to put back on block w pistons halfway so when u spin head valves dont hit.. Now i have never used that headsaver headgasket thing. I used cam tower shims. Both is used to keep the chain tite. So if u use cam tower shims u got to take rockers off and towers. I will let others chime on this that know more. Do you trust this shop. If he did lots of datsuns he know about cam tower shims

He's done quite a few Z series, not sure about L but I trust him I've taken a few heads to him at this point and he's done great work with them. Honest guy, runs the whole shop himself. Do you think the 1.3~mm more slack in the timing chain will be too much/warrant shimming the cam towers?

[banzai510(hainz)]

that is the question i will let you decide. i would have bought the shims but he should have known about them. Put cam sprocket on 2 and see if its timed or if retarted set to 3.

[datzenmike]

7 hours ago, toshts said:

He's done quite a few Z series, not sure about L but I trust him I've taken a few heads to him at this point and he's done great work with them. Honest guy, runs the whole shop himself. Do you think the 1.3~mm more slack in the timing chain will be too much/warrant shimming the cam towers?

 

More like 2.6mm of chain slack. There are two sides to the timing chain so 1.6mm X two. 

[banzai510(hainz)]

im not getting the math here.head shaved .026  1mm equel .039

[ggzilla]

Added chain slack will be double. 2 x 0.026 inch = 0.056" or 1.3mm

On 7/14/2025 at 7:53 PM, toshts said:

ended up having to take 26 thou off the deck

 

[toshts]

It doesn't seem like it would be much slack but if it's noticable when I install I'll go ahead and get shims for the cam towers.

 

Also the distributor that came with the l20b core is a dual points style and looks to be in pretty rough shape. I was thinking I'd run my z22 distributor with only one coil and wireset but its a good bit longer than the l series one. No Datsuns in junkyards anywhere nearby to pull from, any recommendations on what to do for a distributor?

[datzenmike]

The Z20 in the '80 A10 and the '80 S110 200sx, other than California, had only four plugs. For '81 they all changed to 8 plug distributors.

 

Using only 4 on an 8 plug distributor is a fine idea and I've suggested this before when EI distributors are not available. If you think the Z22 distributor is longer use the Z22 drive spindle. I think the L20B and the Z series spindles should be the same but you never know.

[toshts]

25 minutes ago, datzenmike said:

The Z20 in the '80 A10 and the '80 S110 200sx, other than California, had only four plugs. For '81 they all changed to 8 plug distributors.

 

Using only 4 on an 8 plug distributor is a fine idea and I've suggested this before when EI distributors are not available. If you think the Z22 distributor is longer use the Z22 drive spindle. I think the L20B and the Z series spindles should be the same but you never know.

 

The z series is a decent bit longer but I think your right about the drive spindle length, you posted a pic in a different forum many years back that showed them side by side. 

 

 

Here's a z24 dizzy next to the dual points one off the l20b. The z22 one is a little shorter but still a good bit longer than the l20b one. 

 

 

z24 distributor fully seated in the l20b timing cover

 

 

Dual point fully seated internal view

 

 

z24 fully seated internal view.

 

Mainly worried about how high it sits above the pedestal but I could probably make a spacer for it? Pedestal on both the z24 I have sitting around and my z22 look shorter than the one on the l20b so I don't think just swapping them will fit better.

[toshts]

I'll test fit the different distributors and compare the spindles when I pull the motor out.

[datzenmike]

 

I never kept track of them. Wonder what that long one was out of?