All pistons have different Deck

[montelibre]

I have been put the Bulltear custom pistons into the block, but all the pistons are a different deck (about +0.09 mm, +0.20 mm, +0.36mm, +0.15mm,+ 0,20mm, +0,15mm).
What is happening?
I wanted to have zero deck.
I bought a MLS victor reinz head gasket, however at this moment I don't know if is better to put a Perma-Torque head gasket.
I am thinking to lower the top of the pistons for to obtain zero deck and install the MLS head gasket.

[SilverXJ]

I wouldn't blame the pistons.

1) Where are you measuring the piston? To compare bores you need to measure the piston directly over the center line of the rod pin. If not you will get piston rock that will throw your readings off. And even then you may still a bit of rock that changes the readings.
2) Are you 100% sure you are at TDC?
3) The variations maybe normal. You have to take into consideration all the parts that create the deck clearance. The crank, the throws could be a little off; the rods, they may not all be 100% the same length; the pistons, the compression height may vary between them; and the block, it could have been decked at an angle.
4) Are these numbers above the deck, e.g the piston is sticking out of the block?
5) Was the block mocked up prior to decking it or was math done to figure out how much to cut off the deck?

[montelibre]

I have measured the pistons over the center line of the rod pins (at TDC, with good approximation)
The numbers are above the block, the pistons stick out of the block.
The block doesn't have any modification, I bought the pistons thinking to get zero deck. I thought that all the pistons should have same deck.

[Jeepsr4ever]

Your block deck must have been reworked. Also pistons are within .0003" of matching height so it would be in your rods (which may have been resized to reduce length by .004") or your crank is slightly bent. Were you running NOS or induction? Also if they are above care must be taken however this may be an ideal situation. If you find that you have at least .035"+ of quench left over after the gasket you are golden.

[montelibre]

I was running with a MP90 supercharger a few miles, maximum boost about 4.5 psi.
So my calculations are (with 0.043" ticknees MLS Victor Reinz and Bulltear pistons dish volume 34 cc):
Quench = 0.0288"
CR = 8.85

Is it safe quench?
Are the calculations good?

[Antifreeze2]

I'm a new guy here who has yet to build a stroker.

From what I have read, optimal quench is between .040 and .045. Pistons with a deeper dish can not handle higher compression(ICC 944 21cc dish can take 9.5:1 compression, where 945 10cc dish can take 10.0:1). When designing an engine, I hear 10:1 is max for cast iron heads, 11:1 for aluminum. When running NOS or Boost of any kind, you should reduce the compression ration by 1, so 9:1 cast iron, 10:1 aluminum.

Again, I am new to this and all I know is internet theory. Please point out any of my mistakes.

[SIXPAK]

Maybe 10 to one for iron head on pump gas and 11 to one for Alm head on pump gas. Otherwise this is totally untrue.

[Jeepsr4ever]

Yes, run the pistons at .028. If you were running 2618 material and a forged rod I would be more worried starting at .025".

[Jeepsr4ever]

And take some pics of your build!

[gradon]

so you're saying that at least one piston is ~.014" above the deck and with the .043" gasket, you'll have a ~.029" quench? What compression height did you order the bulltears with?

[montelibre]

Yes, I have one of the pistons with 0.014" (0.36mm) above the block.
I ordered the pistons with the deck clearance that I checked with the old pistons (0.025"), to get zero deck.
My engine is a 4.6 Titan , but I do not know if the deck was modified (the pistons was Silvolite 3241HC).
I have just read istallation instructions for the custom pistons and says "we strongly recomended the minimum static clearance between the pistons and head are not less than 0.040 (steel connecting rods)".
I think lowering the top of the pistons to get zero deck, then I can istall the MLS head gasket, so I will be safer...

[gradon]

Bad enough to assume dimensions on a stock engine, but everything that comes out of that Fla. shop should be suspect and double checked.

[SilverXJ]

How are you planning on "lowering" the top of the pistons?

[montelibre]

I will carry the pistons to the machinist to mill the top of the pistons (the shaded in orange)
Each piston must be lowering until to obtain zero deck, the worst piston has about +0.014" obove the block.
I think that only lose about 2 cc of dish volume in the piston that need to be most lowered.

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[herbiehind]

is it really gonna make much of a difference if you just go with the thicker gasket?