440 Pistons 2.061 or 1.990 comp height piston

[Black66post]

I'm building a mild 440 for a 66 street coronet. Factory HP manifolds, factory 69 intake, 3:23 gears and a 275/284 .462/.482 comp cam. Ported 906 heads 2.08/1.74 with serious port job. I'm considering the taller 2.061 six pack piston instead of the 1.990 magnum version. I'm running LY rods. Any thoughts would be appreciated.

 

[NOSTRT980]

looks like you should be ok with the 2.061 CR pistons. 3.75 crank right so that's 1.875+rod 6.76+ piston CR 2.061=10.696, Even at 10.70 deck the piston would be below the deck, just check valve to piston clearance to be sure.

 

[Black66post]

I like the taller Pistons, was just worried about running it on pump gas.

 

[NOSTRT980]

head cc's and gasket thickness?

 

[451Mopar]

The taller compression height, still under 10:1 with 906 heads if not milling the block/heads.
Try to find something lighter than the Speed Pro/TRW pistons. Ross, JE, SRP, and might consider the thinner 1/16" ring pack too, but it will be a bit more expensive.

 

[Black66post]

Heads will be 88cc 906 may need a tad milled for straightness, not milling block. Compressed gasket is .027

 

[lewtot184]

neither. quench dome pistons or change the heads.

 

[Garys1969RR]

I agree, you want a good quench/squish of around .040". Even with the 2.061 pistons and 906 heads, your at .021" below the factory spec deck. And with the 906 recessed squish area of around .120", .020 gasket, .021 below deck piston, you have a huge .161" of squish. With those 2.061 pistons use the closed chamber heads such as 915 or Eddys, with a .020" thick gasket would get you .041" squish. Or use a quench dome piston as lewtot suggested.

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Read the United Engine and Machine tech bulletin on quench for some insight on whats going on in there when the plug fires, and the importance of good quench distance with todays gasoline.