Are head and cylinder gaskets compression gaskets? |
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Are head and cylinder gaskets compression gaskets? |
stevegm |
Oct 22 2016, 01:04 PM
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#1
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Advanced Member Group: Members Posts: 2,111 Joined: 14-July 14 From: North Carolina Member No.: 17,633 Region Association: South East States |
I need to remove the heads off of a newly rebuilt engine (4-cylinder) I built (never run). They have already been torqued. Are the head gaskets and gasket between the cylinder and block, compression gaskets that should be thrown away (i.e., replaced with new one) after I untorque the heads?
The head gaskets will be easy to replace. But I'd have to pull the cylinders to replace the ones between them and the block. |
HAM Inc |
Oct 26 2016, 09:33 AM
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#2
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Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
The reason VW said to stop using the head gaskets is, the differences in expansion rates of the bi-metal relationship between the heads and jugs combined with the inevitable shuffling (relative movement between the heads and jugs) during operation causes the laminated aluminum gaskets to delaminate. That buletin was not written with performance engines in mind, but stock.
Once they start delaminating, they allow combustion gasses to escape, which quickly etches a big path that very often leads to serious damage to the head. Here's the reality about lapping jugs into heads: If the finish in the heads from the flycutting is rough the lapping will smooth it, but if the surface is so rough that it needs that then how much confidence do you have in the machine works accuracy with regard to both chambers being the same height AND on the same plane. Also, lapping will remove metal from the heads, but do little if anything to ensure the jugs are flat. If you choose to lap, make a paste out of ajax and count your revolutions so you can use the same technique on each postion. If a light lap doesn't clean up the both surfaces, time for a trip to the machine shop. Many engine builders toss the gaskets and spray the heads with aerosol coppercoat a few minutes before assembly. Overspray will not hurt anything. That's the low down on gaskets. Proceed with your engines as you wish. |
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