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I'm installing a piston set in a Skoda Estelle 120 engine. I know this is not a definite way to measure piston to deck clearance, but it jumped to my mind to measure it with a vernier caliper using its rod to measure depths: all pistons are about 1.4 mm under the cylinder liner top. This is what the manual says:

Bore x stroke (mm): 72 x 72 Cubic capacity (cc): 1174 Compression ratio: 9.5:1

Not a word about piston deck clearance. So question is: is 1.4 mm under deck acceptable? I know it affects compression...would it mean it will be a bland engine? What PSI a compression test would yield, more or less?

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EDIT: this ain't Porsche :) but I'm reading in Porsche 911 the deck height should be between 1 and 1.5mm, with a 75 mm bore

  • I don't have a "qualified" answer for you, but if there's nothing sticking down into the cylinder space on the head (ie: valves), you should be golden. – Pᴀᴜʟsᴛᴇʀ2 May 7 '17 at 2:37
  • I just thought the ideal deck clearance was zero or near it...1.4mm seemed to me very bad. The valves doesn't get into the cylinder (but will check for the fun of it) – Aram Alvarez May 7 '17 at 2:47
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    Most engines from the factory aren't zero decked. For performance reasons, a lot of engine builders will cut the deck to get it to zero, but yah, it's not that usual from the factory. Since I have absolutely no experience with the engine you're working on, I really don't have an answer for you. I'd suggest since everything you are running is more or less stock and all of them are measuring about the same, everything is probably spot on. – Pᴀᴜʟsᴛᴇʀ2 May 7 '17 at 2:50
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Do the calculations: you have bore & stroke and compression ration. You could work out the volume in the cylinder head. Then you will know if they match.

The workshop manual should tell you what the compression test values should be.

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