Building my first VW/Porsche flat engine in 30+ years, I am taking my time checking and double checking. The $$ investment is not that great, but I want to get it right. Case is together with good main, rod and cam clearances. Engine spins, not too loose, not too tight. Assembling the pistons and cylinders I added some short sections of 1/2" pipe and loosely tightened the cylinders to the case. Checking across the tops of the cylinders with a straight edge I was getting a rocking on #3 and #4 (about .008 at one end with three contact points at 0). Took everything apart and cleaned all mating surfaces, now I am getting about .002 or so. I did not send the case in to a machine shop for checking all the mating/bearing surfaces.

I am thinking several small pieces of Plasti gage on the tops on the cylinders/head surface to check % of mating surface. I have lapped the cylinders to the heads.

Happy New Year to all, enjoy in good health

I'd suggest pulling the case apart and sending to shop to have the cyclinder registers surfaced.

On both my cases, on the cylinder registers, I found about 0.005" of variance that had to be machined out by taking of 0.010" to ensure flatness.

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In this photo you can see material partially removed but still has low spot until final cut was taken
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0.010" final cut
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This is a very common problem on 50 year old cases. Many of which have been overheated at some point in their lives. I think Raby sometimes was cutting up to 0.025" to ensure flat and square to crank centerline. Don't quote me on the Raby number, but it was more metal removal than I had to do on my two cases.

Even if you get down to 0.002", lapping won't take that out. Lapping by definition is for removal of material on the order of 0.0001" or 0.0002" (ten thousandths of an inch).

Again if you could lap out that 0.002" locally, in just that spot of the cylinder to head contact, you would have to have that cylinder perfectly clocked to the head later on upon reassembly to get a good seal. Not worth the risk of not having good sealing. With no head gasket between cylinder and head, plus thermal cycling plastigauge is only a snapshot in time. When you get a leak between the head and cylinder you get oil leakage.

Even worse, engine can run lean since you're pulling air right into the cylinder between head and cylinder, completely bypassing your induction source. Engine then starts overheating that cyclinder and the spiral of damage all begins anew.

@930cabman

On my 2056 build I had the same issue. Len Hoffman at HAM decked the case and took off .008 to get things back to square. Def send it to someone who's familiar with this operation and has the right jigs and equipment to do the job at a high level of precision.

FWIW, 0.001" = 1 mil = 1/1000". 0.0001" = 0.1 mil = 100 microinches. 0.010" = ten thousands of an inch.

Happy New Year.

Nothing you've said is wrong.

However, don't try that lingo with your local machinist.

0.001" is a Thousanth on an inch or One Thou. 0.010" would be called Ten Thou or Ten Thousanths as you've correctly stated.

0.0001" is one ten thoundanth of an inch. 0.0001" is called a "tenth" in machinist lingo. 0.0005" is called Five Tenths. Five tenths is equal to 1/2 of One One Thousandth on an inch (0.001"/2 = 0.0005").

Unless you're very explicit about whether you're dealing in imperial units or metric 1 mil can also mean 1 millimeter.

1 millimeter = 0.039370110". That is Thirty Nine thousandths of inch (and some change). Very often 1 millimeter will be rounded to 0.040" or Forty Thousanths of an inch or Forty Thou. So you don't definately don't want to confuse the guy between the imperial or metric.

If we are known to be dealing in metric, Ten mil = 10 millimeters as in hand me that 10 mil socket.

Be careful out there!

Very good then. I've worked with machinists for over 40 years on everything from space based x-ray telescopes to DNA sequencer optical systems. Interferometric metrology was one of my specialties. It's all defined in the CAD file. Happy New Year!!!

BTW, thanks for the input.

I was able to try the Plasti Gage method earlier and all appears good. I applied a tiny dab of grease to hold the plasti gage in place, then set a small (about 1/2" long) piece of the plastic gaging material at four locations on the top of the cast iron cylinders. Torqued everything to 25 ft/lbs and when I pulled it apart every piece of the Plasti Gage was flattened to near zero. I will check with a local VW trained (40+ years ago) machine shop operator tomorrow to get his .02

From my lay understanding on the subject, I would call this a success.

Thanks all for your feedback

Next engine build I will definitely have all surfaces checked prior

Checked with 2 different local old school VW engine builders today and both confirmed if the cylinder/head mating surfaces are within .002, use the head gasket as furnished with the Reinz kit. It measures .03, adding a cylinder base shim of .01 and a 56cc combustion chamber my compression ratio will calculate out to 8.7.

Mr Elgin furnished a 266 duration cam and suggests a comp ratio between 8.5 and 9.0

Many here do not recommend using a head gasket, we will be using one