engine clearance question

[UNATUL APIRTED]

i am getting my block machined and it is being decked. i measured the piston to deck clearance and it has .006" above the deck of the block already. i was wondering what the spec is for piston to valve clearance? since it doesn't seem like there is a spec for piston to deck clearance? also what is the stock headgasket thickness. Thanks

[Guyana00]

You have to measure the total height of the block and head. Subtract those from the stock height and that is the total amount remove from both the block and head. Make it up wit different thicknesses of metal headgaskets.

[UNATUL APIRTED]

that just doesn't seem like an easy way to find your headgasket thickness. there should be a spec for at least piston to valve clearance and thats really all i need to know what size headgasket to use after the machining has been done

[SupraTuned]

Its alright my friend! Go with Cometic! They are a great company, they have all of the specs for our cars, and they will custom make the size you need, with all appropriate tolerances. All you need to do is add together the amount taken off of your block (don't forget the timing plate on the front of the engine like I did!), the amount (if any) taken off of your head, convert it to mm, and add 1mm for stock thickness and tell them that is what you need when compressed. Price is a about 60 more, but well worth the exact match. I didn't really know what to do either when I had to do mine.

[Guyana00]

First off, it is very damn easy. Two measurements. Even if for some reason you're going to struggle, get the machine shop to measure it more accurately than you would and there, no work involed.

Work a few number assuming you know how you add or use a calculator and you have your gasket thickness. Even if it weren't that easy, when you're doing the headgasket, especially on them 7M you need to do it right or don't bother or you'll be back in this position or worse in short time.

Make sure the front plate is machined along with the block as mentioned, depending on what mhg you go with make sure the RA is within spec for that HG.

When it's done right you'll be glad, you can turn up the boost, abuse your engine and never turn back.

[UNATUL APIRTED]

yeah i will know how much is taken off of the block but i am buyin a re-man head because my cam journals are scored...so i have to replace it. so i guess unless i have a spec for the head height or whatever i will not know... is there really not a spec for piston to valve clearance or is that just not the way to go on the 7mgte engine??

[Guyana00]

Here are some number that will help you determine the correct headgaket thickness. Valve clearance will be stock or within spec as long as this formula is followed.
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Stock head height = 116mm deck to valve cover surface
Stock block height = 198.5mm deck to main crank saddle
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Next, measure you head and block height, from the same spots, get your machine shop to do it if you cant and tell them where to measure from.

Then, subtract is from the stock heights.

Add those together, add 1.37mm for stock HG thickness when compressed. Buy the appropriate headgasket, if there isn;t one close enough, for about the same price comeitc will make one for you.

While you're at it see if your cylinders are going to be bored. This will be an important part of choosing the headgasket, stock bored is 83mm, even if it's not going to be bored, get your machine shop to check it in case it was previously done.

EXAMPLE:
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Your block height AFTER machining and RA spec is met is 198.00mm (don't forget the timing plate.
You head height AFTER machining is 115.37mm

198.5 - 198.00 = 0.50mm
116.0 - 115.37 = 0.63mm
Stock HG = 1.37mm
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Total = 2.5mm

Consider your cylinder bore as you need cylinder bore AND thickness when consider gasket size. As I said, if there is no appropriate pre-made gasket for you, get one made. You do it like this and the head and block are within the RA spec, install it properly and you never need to look back.

[UNATUL APIRTED]

ok thx for the help.. i just figured that usually the easiest way to figure out headgasket size is the piston to valve clearance but ill go that route since ive herd a few people talk about doing it that way. i am just having the cylinder bored honed out since i had great compression to start and the walls are almost new.. just need new cross-hatches, doing rings and bearing.