I'm in the process of re-assembling the top end of my stock 2.0 liter four, and I have measured deck heights as follows:
#1 - 0.036
#2 - 0.029
#3 - 0.037
#4 - 0.035

These measurements are with the cylinder base sealing rings in place and the cylinders torqued down snugly and measured with a dial gauge. To me it seems as if I need to add a shim to the bottom of cylinder #2 approx. 0.050 - 0.080 to increase its deck height to within the range of the others. I have a couple of used 0.080 shims, one of which I could add to cylinder #2 to bring it up to 0.037.

I have a couple of questions about this.

First, how much variance is permissible between the measurements? If the deck heights are all within 0.002 of one another, is that Ok or do they need to be exactly the same.

Second, can I re-use one of my 0.080 shims or should I source a new one.

And third, do I place the shim on top of the cylinder sealing ring, beneath it, or doesn't it matter. I was planning on putting it on top of the sealing ring.

Thanks in advance for your advice.

Have you measured the individual cylinder heights? Or piston pin to top of piston? I'd be looking for where the variance is. If the cylinders heights are all different I would pay a machinist to make them the same ""height" . get new gaskets when assembling. Most everyone does not use cylinder to head sealing ring.

I know just enough about engines to get myself in trouble and I’m sure the gurus will reply, but you ideally want the deck height to be consistent. Shims should added To control the compression ratio...not make up differences.

Did you have you case 'decked'?

No. Case has not been decked, as this was supposed to be just a top end inspection and refresh with new rings, gaskets, and seals. Should have measured deck height before taking it apart. There might have been a cylinder base shim under #2 to begin with. Haven't measured cylinder head volumes yet, but they also should be consistent so the deck heights should be consistent also so that the compression ratio is the same for each cylinder. At least that's my understanding. If I were doing a total rebuild, I'd definitely get the case decked.

I haven't built a type 4 in years, but I do know that the cylinder registers can sink and cause a problem. I'd carefully measure the cylinders and put a precision straight edge across the case registers to make sure it's nice and level.

Either way, you need to find out why there's difference.

I fought mine for some time scratching my head because register and barrel didn't explain the difference I was seeing and finally figured out it was the distance from wrist pin bore to piston top making the difference. And that was on old OEM Mahle pistons purchased new in the early 80s!

No. Case has not been decked, as this was supposed to be just a top end inspection and refresh with new rings, gaskets, and seals. Should have measured deck height before taking it apart. There might have been a cylinder base shim under #2 to begin with. Haven't measured cylinder head volumes yet, but they also should be consistent so the deck heights should be consistent also so that the compression ratio is the same for each cylinder. At least that's my understanding. If I were doing a total rebuild, I'd definitely get the case decked.

All I know is you want a minimum of .040”” clearance so order shims to set it correctly

The individual deck heights are less of a concern than having each pair of cylinders even. I use to make a tool to do this, but you can probably work something out with a straight edge, some spacers, and the cylinder head nuts.

Correct. I also agree with the .040" minimum deck, you have to know what you're doing to set it any smaller.

Try swapping piston #2 with #3 and see if it makes a difference.

I picked up one of your tools used. Were there any write ups or instructions on how to use it? I found the original pictures and see how it’s bolted up and seen how the plate locates over the pistons. What type of mounting is used for the dial indicator?

Where are you measuring the deck height? I assume near the perimeter of the piston? If so, there can be variation due to rocking of the piston, so a single measurement point can yield a range of inconsistent values. It's good to measure at opposite sides of the piston and average the readings. One easy way is to put a small strip of solder on each side of the piston crown, torque the head on and measure the crushed solder.

Edit - should have mentioned that it's best to turn the engine over to crush the solder.

Aaron I think I inherited one of your tools, is it two machined alunimum bars with a keyed plate that drops in for measuring deck and 4 spacers?

I'm using it for the first time and have to say it's a nice piece of T4 kit.

I was measuring at the edge of the piston, but 90° from the plane of the wrist pin, so I think a rocking piston gave me a poor reading. When I rotated the engine and measured along the plane of the wrist pin I measured the deck height of cylinder #2 at 0.037, a value consistent with the other three cylinders. This is after installing a 0.008 shim on the base of cylinder #2 and putting a straight edge across the top of cylinders #1 and #2 to make sure they are both the same height, which they are. Since I am installing head gaskets that measure out at 0.0035 thickness, my final deck height is right around 0.,040, which seems to be the safe target height. So it looks like I'm good to go. Thanks for advice and help on this. I really should have fabricated up a nice stable plate system to use with the dial gauge so my measurements could have been made more easily and at the correct positions. I'll do that for the next rebuild of my 1.8 liter.

I haven't used head shims since the 90's and I wouldn't use them with 96mm cylinders.
You have to measure along the same plane as the pin.

Are you doing a proper CR?
You should be doing this, CC on the heads, deck height and use a CR calculator.

http://cbperformance.com/v/enginecalc.html

try this ~

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That looks great. How is the dial gauge connected so that you can slide it from the cylinder onto the edge of the piston?

That's the one I have but it also has a plate that drops in between and is keyed to the half circle cut outs you see on the bars. No need to use a dial indicator, a vernier caliper zeroed on the plate is good enough.

Used it again today, got +/- .001 on all cylinders, .041 deck no base shim on KB pistons. Little lower CR than I was aiming for with stock heads, but acceptable so they went in with no shims or head gaskets.

Yup. Exactly how it’s done. I use a depth mic, but whatever works. It also has a lip that lets you measure the height difference between the two cylinders.

Hmmm I didnt get that ? Mark can you post a pic I might have to make one.

I found the old pictures from when I was making these. This should help.

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Yes that's what I have.
I tried to post some pics last night, but win10 was getting stuck downloading from the SD card. I need to get a hardwired wifi router out in my shop.

Great information on this thread …

I hope I'm not highjacking to ask a related question. How high can you get the compression ratio on a type 4 with flat top pistons? I understand people cut the heads to bump it up a bit. What if you want high compression, like, say 11:1? Domed pistons I guess?

Scott

Why 11:1?

Fly cutting is the easiest, you can surface the head fin for more clearance, some remove a fin, other builders have welded the chambers making them smaller.

I don't know if domed T4 piston are available, maybe custom order from JE. You could make you own "dome" if you have the deck to play with, but I can't see getting more than .5cc doing this.

Rich,

I have the plate if you want to take a look at it.
James

Thanks for sharing your thoughts. I'm planning to put together a 1.8L race engine for an old SCCA 914 I just bought. I'm more familiar with 911 engines where 11:1 is no big deal. Is that high for a type 4? Understood that I may need to have custom pistons made.