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Old 11-19-2009, 09:29 PM   #1
mattromey
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Default head spacer or machine work?

so i just got my block and head back from the shop and was told it might be a good idea to either get a head spacer or machine the pistons both options are about the same price. i had to take .020" off my head and .018" off my block so does anyone have any ideas as to what i should do? head spacer machine work or just put the thing together? i just dont know how close Toyota ran the pistons to the valves.

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Old 11-19-2009, 10:58 PM   #2
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Donít put it back together like that, even if you have enough clearance between the valves and pistons. Iím sure you will have issues locating the timing belt correctly on the sprockets for one thing as the head is lower by .038 thou .Compression ratio will also be increased not a good thing with head gaskets on a Supra. I'm sure someone will give you the correct advice soon. A thicker metal head gasket would be my recommendation.
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Old 11-19-2009, 11:12 PM   #3
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Sounds familiar Link
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Old 11-20-2009, 11:13 PM   #4
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so is there a difference between running a head shim and gasket and just running 2 head gaskets, cause as far as i can tell the head shim looks the same as my head gasket.
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Old 11-21-2009, 01:56 AM   #5
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Shim is a single layer and generally compresses less (than a composite that is). Running a shim with a metal HG versus running a thicket metal HG is pretty much the same thing. I *think* the shim would be preferable though in your case. A real thick MHG has a lot of layers and that's a lot of potential for gaps and leaks. A solid copper HG would be the cleanest solution, but I hear longevity is an issue, hence why you really only see them on dedicated race cars.

The question I haven't seen asked or answered is what are you running now and what are your plans? What type of HG do you want to run? If your car is turbo'd are you looking to go to a thicker HG to reduce the CR?
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Old 11-21-2009, 02:11 AM   #6
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i don't plan on doing to much i was thinking 550cc injectors and a lexus afm and may be running 10 psi and 3in exhaust, other then that it will be stock. oh and i got a full set of forged pistons that will now have to be machined down .020 to be below the deck
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Old 11-21-2009, 02:26 AM   #7
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You could see if it would be possible increase the dish of the pistons enough to bring down the CR so you could use a thinner HG and no shim... I don't know if I would though.

Do also keep in mind you need to calculate the new CR after shaving the pistons as the dish will be lessened.
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