Dumb question 512 build
- Thread starter Heimedw
- Start date
Garys1969RR
Well-Known Member
Well that explains it, then. Any material removed from the deck is going to result in the piston being above deck. You could have just used a thicker gasket as Stanton did, eliminating the fly cut and re balancing. Then you can dial in your quench distance/clearance with the gasket thickness. If it's .010 above, just use a gasket around .040. I'm building a 512 also. Same set up as you, except flat top pistons. Pistons will be at zero deck before block surfacing. I plan to have the block cut .010, and use a .040 gasket. I work out all this on the computer beforehand, so I kinda know how to proceed. I'm shooting for around 13 to 1 C/Ratio, as this is a race only motor.
Garys1969RR
Well-Known Member
It can be tricky working out deck clearance, target compression ratio, piston dish or dome, and gasket thickness, getting it all to match up right. I go thru many different combinations on the computer, using the KB pistons C Ratio calculator. It's actually kinda fun! I'm currently trying to get a 383 stroker , flat top pistons, to come out at around 11.5 to 1. Only way is to deck the block .015, and use a .020 gasket. Plus will need to mill the Stealth heads to 72 cc chambers. I'll be using the ICON pistons from our 496, as they can be used with a 3.75 inch stroke in a 383 block with a 6.76 440 rod. They come out .025 below a stock deck. By the way, I believe 440 source uses ICON premium pistons in their stroker kits.
PurpleBeeper
Well-Known Member
I'm too lazy to calculate...… but, it's basically 8 x cylinder volume, which includes thickness of the head gasket, stroke, piston volume, combustion chamber volume, etc. So.....if there is no other change than the heads, & combustion chamber volumes are 88cc (?) & 78cc (?), then your CID of the engine is 8 x 10cc = 80cc = about 5 cubic inches smaller with closed chamber heads vs. whatever you had with open chamber heads.
Hemirunner
Well-Known Member
It’s 440 cubic inches regardless of what head is on it. Hell, it’s 440 cubic inches with no heads on it.
PurpleBeeper
Well-Known Member
Hmmm....maybe I'm wrong on this. So, are you saying the cubic inches of the motor does not include the combustion chamber volume (& head gasket)????
Haven't you been reading any of the posts !?!?!?!? Yes, you're wrong - for about the fifth time ... CUBIC INCHES DOES NOT INCLUDE COMBUSTION CHAMBER VOLUME
Garys1969RR
Well-Known Member
Cubic inches is swept volume. The combustion chamber is not part of the swept volume.
Lelo 500
Well-Known Member
You must be thinking of compression ratio.
68 HEMI GTS
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Wow, that stroker kit puts the piston at the stock deck height (9.98). If you are blueprinting a block one of the steps in to square the decks and make them equal. Yeah I see how they had to mill the top of the pistons. I'd rather mill the pistons than rely on a thicker head gasket.
It's always something. I just had to turn .050" off some bolts for my new Rally center caps so the rim sit flush on the hub.
It's always something. I just had to turn .050" off some bolts for my new Rally center caps so the rim sit flush on the hub.
68 HEMI GTS
Well-Known Member
Sometimes they sit a bit proud. No worries, they run well like that.
Garys1969RR
Well-Known Member
I thought they might! Chrysler was maybe testing out an idea when they built that 1 year 383 Magnum with a positive deck piston. I will have a positive deck height in my 512 build.
Challenger340
Well-Known Member
OK, must have missed that it was a 400 Stroker Kit somewhere ?, and yes.... those Kits don't leave much Block deck height "room" for Milling.
Still, machine setup should show immediately before Milling, just where the Block is at Height-wise, most 400's being above 9.98" nominal from factory
and,
we don't get our panties all in a knot about trying to maintain sub .050" quench when using a DISH Piston ?
I mean think about it for a second ? Like what for ?
All you are doing is trying to blow the "cooling/quenching" effect over into the volume of the dish ? which the Int/Exh/Cam ratio is already struggling to scavenge.
Off Topic....
but has anyone actually Dyno tested timing advance effect using Dished Pistons vrs Flat Tops at given quench distances ?
We have LOTS !
and would love to have this conversation about "quench" vrs Timing advance using Dish Pistons, let be the entire sub .050" quench distance 4.00" Bore thing on larger 4.300"+ Bore dimensions like a BB Mopar with Valves entering on the backside of the Cylinders.
So if your Pistons are slightly positive deck and you are worried about "quench".... why not just substitute the Fel-Pro 1105 .051" Head Gaskets ?
Who cares if the Pistons are slightly outa the holes ?
Yup !! Those gaskets are pricey but cheaper than milling pistons !! And if the block has the proper finish, Cometic MLS gaskets can be had in custom thicknesses.
Heimedw
Well-Known Member
My best guess is that they did it to lower the compression a little. The kit says it should have a compression ratio around 10:39:1 with a 78cc head and stock deck height. I'm using TF 240's and a lot of people say they usually cc around 76cc. We also took .010 from the deck so that will raise it even more. I'm at seal level where I live and our fuel is crap! So my builder said we are going to be right on the edge. The only other thing I can think of is my block had three cylinders that had to be off set bored. So maybe it was for head interference? That's just my guess I will find out tomorrow.
Don Chapel
Well-Known Member
I am using the .051 head gaskets. .005 out of the hole on the 512 from 440 source. certainly wouldn't mill the pistons.
