Aluminium head gasket thickness

[POPO1984]

Does anyone recomend a .030 compressed head gasket for aluminium heads. my stack is currently .015 in the hole

[kpeztruck]

My only concern is piston-to-valve clearance. I won't run mine under .100" Paul Baxter

[POPO1984]

Well i have no idea at this point what my PTV clearance will be. Im assuming it will be ok since i have dished pistons. the reason im asking is i thought i read something about fretting and a thicker gasket

[Super73]

Originally Posted by kpeztruck

My only concern is piston-to-valve clearance. I won't run mine under .100" Paul Baxter

Really? A .100 gasket? Mind answering a few things for me.

Compression Ratio (Head CC's)
Cam grind (Manufactures specs) Is it installed straight up or did you degree it? If you did, what intake centerline did you put it on?
What is your total timing?



Popo, dished pistons are one thing, but I am assuming there are valve reliefs in the pistons? I currently run a .045 in mine but I am toying with pulling the heads off and bringing mine down to .020. I would rather run a thiner gasket than mill the heads (Leave room for later milling if you need it). As long as piston to valve clearence isn't an issue, you should be ok.

I'm assuming your heads are not on the motor right now. My advice would be to buy a cheap single gasket for mock up. Clay the piston and torque the head down to compress the gasket fully. Turn it over by and and see what P to V is. If you are using a hyd lifter, find a way to make it solid or find a buddy with one sitting on the shelf you can "mess up" If it's not solid, you are going to get a false reading.

[mongoose]

im pretty sure he means 100 thou from piston to valve... he's prob running a normal 40 thou quench..

[stich626]

I'd install the gasket and bolt down the head(no need to torque it down..
with clay on the piston top and pam on the valve heads
run the engine around to open the valves(i'll need a solid lifter) .then pull the head..
the clay will tell you how much clearance you have..
- the difference of the new gasket and the compressed gasket..
if you have the piston to valve clearance.. your fine..
if not and your dead set on use'n those gaskets. you can have the pistins fly cut..
do this before you have the engine balanced..
f.y.i. iron gaskets and alum head gaskets are made different..
make sure the gasket you want to use have the fire rings made for alum heads.
good luck

[POPO1984]

Originally Posted by Super73

Really? A .100 gasket? Mind answering a few things for me.

Compression Ratio (Head CC's)
Cam grind (Manufactures specs) Is it installed straight up or did you degree it? If you did, what intake centerline did you put it on?
What is your total timing?



Popo, dished pistons are one thing, but I am assuming there are valve reliefs in the pistons? I currently run a .045 in mine but I am toying with pulling the heads off and bringing mine down to .020. I would rather run a thiner gasket than mill the heads (Leave room for later milling if you need it). As long as piston to valve clearence isn't an issue, you should be ok.

I'm assuming your heads are not on the motor right now. My advice would be to buy a cheap single gasket for mock up. Clay the piston and torque the head down to compress the gasket fully. Turn it over by and and see what P to V is. If you are using a hyd lifter, find a way to make it solid or find a buddy with one sitting on the shelf you can "mess up" If it's not solid, you are going to get a false reading.

My main concern is getting a good quench. My stack is currently .015 in the hole so i was thinking of using a .030 gasket.

[stich626]

what pistons, dome/flat/dish
is decking the block for zero down the hole on the table or not

[POPO1984]

im using 16cc dished pictons.

[Super73]

Originally Posted by mongoose

im pretty sure he means 100 thou from piston to valve... he's prob running a normal 40 thou quench..

Could be.. I might be reading it wrong..

Originally Posted by stich626

no need to torque it down..

Gaskets compress under torque. You will never get a exact reading if they are not torqued.

The other reason I'd torque them down is to make sure your not taking the head out of square if it has been milled and is currently in square.

[regan wilson]

40 to 45 quench is fine, 100 thou piston to valve with a stainless valve . 85 thou or better on a tit valve. (and good valve springs)

[Marv D]

Yeah I'm totally confused. Is he looking for piston to head clearance (quench), or valve to piston. I've seen guys run .020" piston to head and get away with 8500rpm (with steel rods). Upon teardown there was only a 'hint' of witness things were 'close' (LOL) To me it's NUTS, but what can you say. I'm of the mind a true zero deck, steel rods and all you need is the 0.039' gasket.
Like Regan I try for .1" for a steel exhaust valve, and .085 (yes, adding the zero the missed) for exhaust. I'm sure you can tighten it up for the ti. valves, but after stretching out a chain with the big spring pressures,, and having tagged 8 valves at $120 a piece I wont be skrimping on VtP clearance and thats a fact!!! LOL

[Super73]

I believe he is saying pistons are in the hole, so head to piston clearence should not be an issue. I think he is asking if running that thing of a gasket is ok.. Simply, yes as long as piston to valve clearence is ok.

[POPO1984]

thats what i was hoping super73. thanks

[stich626]

Originally Posted by Super73

Could be.. I might be reading it wrong..






Gaskets compress under torque. You will never get a exact reading if they are not torqued.

The other reason I'd torque them down is to make sure your not taking the head out of square if it has been milled and is currently in square.

yes you will, that why I said take the gasket thickness and - the compressed thickness.. then take that off your measurement..
both the gaskets thicknesses are readly avail..
and it's easy math..
and cheaper than killing a gasket for a p/v clearance test..

[kpeztruck]

Originally Posted by mongoose

im pretty sure he means 100 thou from piston to valve... he's prob running a normal 40 thou quench..

Exactly, I was talking about piston to valve clearance. I am currently running an .080" compressed thickness gasket on the engine in my index car. I plan on trying a few things on the truck motor next year. Maybe I can pick up a little power! Hopefully this answers the other gentleman's questions. Paul Baxter

[Super73]

Originally Posted by stich626

yes you will, that why I said take the gasket thickness and - the compressed thickness.. then take that off your measurement..
both the gaskets thicknesses are readly avail..
and it's easy math..
and cheaper than killing a gasket for a p/v clearance test..

He would still have to compress a gasket by torqueing down the heads. Even if he took and put a caliper on a non compressed head gasket to get uncompressed thickness, as soon as any tightening of the head to block with the gasket inbetween, there would be some form compressing going on. Even if it was .005" it would still have a little bit of compressing. If he used his uncompressed thickness based on the caliper of mfg's spec sheet to base his math equation on, it would still be off. Because the gasket got slightly compressed when tightening the heads down.

Now let's assume he brought the bolts to 0 lash and didn't "tighten or Torque" the heads down at all. If those heads are not square, the readings are going to be off.

Call me anal and over thorough but I prefer to take measurements as it would be run. That is the only way to be sure.

I am saying to use a cheap gasket, compress it fully by torqueing it down (You'll know what that thickness is from the manufacture), pull it off and check your clay.