 Deck Height Question |
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| clarkcou |
 Nov 28 2020, 09:16 PM
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#1
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Member  Group: Members Posts: 115 Joined: 17-October 03 From: Peoria, Arizona Member No.: 1,257 Region Association: Southwest Region  |
Building a 1.7, 90 mm piston/cylinder. With no base gasket, deck height is .013in. Shouldn’t the head gasket/ shim be included in the deck height.
Barrel shim, not yet installed, is .21mm. Head gasket is .068. Seems to me that deck height would be.082 without barrel shim. I.e. .013 plus .068. Thoughts on this please? Randy |
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| Robarabian |
Nov 28 2020, 10:10 PM
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#2
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914 A Roo Group: Members Posts: 592 Joined: 11-February 19 From: Simi Valley, Kalifornia Member No.: 22,865 Region Association: Southern California 
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They sell a kit to help with it... a deck height measurement kit. No head gaskets / shims. Put the base shim and assemble the cylinder. Using the kit, it will bolt down under pressure (torque spec not necessary but likely used) and measure the deck height. You want .040 to .060.. somewhere in that range. Do the math and calculate the base shim you will need to meet the deck height. Make sure you take the CC of the heads into consideration for compression ratio calculations...
Have fun! QUOTE(clarkcou @ Nov 28 2020, 07:16 PM)  Building a 1.7, 90 mm piston/cylinder. With no base gasket, deck height is .013in. Shouldn’t the head gasket/ shim be included in the deck height. Barrel shim, not yet installed, is .21mm. Head gasket is .068. Seems to me that deck height would be.082 without barrel shim. I.e. .013 plus .068. Thoughts on this please? Randy |
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| VaccaRabite |
Dec 1 2020, 11:59 AM
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#3
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En Garde! Group: Admin Posts: 13,444 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
QUOTE(Robarabian @ Nov 28 2020, 11:10 PM) They sell a kit to help with it... a deck height measurement kit. No head gaskets / shims. Put the base shim and assemble the cylinder. Using the kit, it will bolt down under pressure (torque spec not necessary but likely used) and measure the deck height. You want .040 to .060.. somewhere in that range. Do the math and calculate the base shim you will need to meet the deck height. Make sure you take the CC of the heads into consideration for compression ratio calculations... Have fun! The old school way to do this is not to use a kit, but to use 2 sockets that fit over the stud and use them to bolt down the cylinder to measure deck height. Also DON"T JUST PICK A DECK HEIGHT! Deck height is only a part of your Compression Ratio calculation. You want to pick a CR, and then use Deck Height to get to it. Don't just build to the smallest deck height and hope for the best. I've done it. And I've torn the engine down a few months later too. .040 is the minimum safe deck height in terms of valves not hitting pistons. You can build an engine with too little deck, which equals too much CR, and be constantly battling overheating heads. Being forced to drive around in 4th all the time or watch head temps hop over 400 degrees SUCKS. Zach |
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Posts in this topic
clarkcou Deck Height Question Nov 28 2020, 09:16 PM
Montreal914 I am sure others will chime in but per Porsche bul... Nov 28 2020, 09:48 PM
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