possible issue with shaved heads and compressed gasket thickness.

[85begalttype]

85 hotair motor, getting the motor rebuilt from a wiped cam lobe and very low oil pressure. Last year when i tore the motor apart, i was researching and decided to use the felpro1000 gaskets with a compressed thickness of 0.039 in. I brought my heads to the machine shop to get shaved down 0.010. As i read from someone on the board that the stock gaskets are a bit thinner, and that the heads will need to be shaved to match the compression ratio.
Now i read that the STOCK head gaskets compressed thickness is .063". So maybe im thinking i messed up and should have just got the 9441pt gaskets.
Now i am coming closer to the day when i bring my block in to get the bottom end rebuilt, am i fine with the 1000 gaskets and 0.01 shaved off? i made myself all confused and hoping i didnt make a mistake bringing my heads in...

 

[bison]

The compressed thickness of the stock steel gasket is .017. Idk where you're getting your numbers from. The stock pistons sit further in the hole because the deck is taller on a 84-85 and the result is still 8:1. .010 off the heads does little to the CR. With the gasket you are using it will be under 8:1. I'd do whatever I could to get a higher CR if it were me.

 

[Nick Micale]

I have available a set of original GM steel shim gaskets which were used on '84-85 turbo engines if you need them.

 

[85begalttype]

thanks , i will most likely be using the rjc gaskets then. unless i can reuse gaskets that were installed and torqued but engine never started?

 

[Turbo-Archie]

The stock pistons sit further in the hole because the deck is taller on a 84-85

Is the CH the same on '84-85 pistons as it is on '86-87' pistons?


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[turbofabricator]

You can re-use the head gaskets IF you put them on the same side with the same head. It may not really matter but it would be best. If the engine never ran they wouldn't have been heat cycled so they will be fine. I have done this a few times when I had to pull the heads to deal with an issue. Never caused a problem. I have re-used Cometic gaskets 3 times with no issues on a 700+ HP engine. This build they are being replaced because we burned a spark plug and it did alot of damage to pistons and head and I'm a little nervous about reusing them again. They looked perfect, but............

 

[bison]

Is the CH the same on '84-85 pistons as it is on '86-87' pistons?


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I never checked the dish or compression height on an 84-85 but am fairly certain the total clearance volume is the same. They bothnuse the same stroke.The taller deck uses a thinner gasket. It should offset . If you want to cc the top of the cylinder with the piston at tdc and cc the head combustion chamber I can give you a very close number.