• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Dumb question 512 build

Heimedw

Heimedw

Well-Known Member
Local time
4:00 PM
Joined
Aug 23, 2014
Messages
263
Reaction score
106
Location
Ontario
This may sound like a dumb question. I'm sure some of you are following my 512 build. The machine shop had to deck the block 10 thou and had to machine the top of the pistons for 0 deck. My question is would this effect cubic inch of the engine and is there a way to calculate the change? Also I would assume that when the block was line honed this would also bring the pistons up to the top of the cylinder more. I know that bore and stroke calculates cubic inch but is piston area also a factor? I would assume it does or am I wrong?
 
C.I.D. Is the bore and stroke, namely the amount of volume. Any milling of deck, pistons, heads,etc affects compression ratio. Also, milling of deck and heads affects the geometry of the mating of the intake manifold.
 
Machining the pistons was an unnecessary operation and expense. Zero deck is not the important thing, what you want is the targeted compression and quench. In your situation, you could have just used a thicker head gasket. Tell me who did that so I never use them - they're just sucking money out of you.
 
Heimedw said:
This may sound like a dumb question. I'm sure some of you are following my 512 build. The machine shop had to deck the block 10 thou and had to machine the top of the pistons for 0 deck. My question is would this effect cubic inch of the engine and is there a way to calculate the change? Also I would assume that when the block was line honed this would also bring the pistons up to the top of the cylinder more. I know that bore and stroke calculates cubic inch but is piston area also a factor? I would assume it does or am I wrong?
Click to expand...
I will give this question a shot. Yes, it does affect the cubic inches. The piston area, per se, doesn't affect the CID, it's the volume of the cylinder (with piston up vs. with piston down) AND the volume of the cylinder heads.

If you need to know the "exact" CID, you could "cc" the cylinder heads + cylinder with piston up + cylinder with piston down.

If you just want to get "close" you could calculate the new CID, but it's a little tricky. You'd need to figure out the "dish/valve relief volume" of the newly machined piston. You'll also need to calculate the new cylinder volume at zero deck + combustion chamber volume.
 
Heimedw said:
.....My question is would this effect cubic inch of the engine and is there a way to calculate the change?

........... but is piston area also a factor?

I would assume it does or am I wrong?
Click to expand...

No, it will not effect the engine's displacement.

No. Plus, you're not changing piston area. You are effecting slightly total combustion volume and that will have an effect on CR.

It does not.
 
Last edited:
Whether it's 512, 511 or 513 does it really matter?!?! They're all advertised based on stock bore and the crank stroke. My "advertised" 526 is actually 528 because its bored .060 over but who gives a ****. What counts is how it performs. I'd hate to tell someone I have a "528" and get my *** kicked by their slant 6 !!!
 
So bore and stroke determines cubic inch. So then if you filled the cylinders with water and measured it (within the same distance the piston travels up and down the cylinder) you would have your displacement in CI correct? So the combustion chamber should have nothing to do with it but if you deck the block you are technically removing space for wich water can take up correct?
 
Combustion chamber volume is not taken into consideration when calculating cubic inches. Cubic inch displacement is "swept volume" only. Always has been - always will be.

If you wanted to measure "cubic inches" or cylinder volume with a head in place you would bring the piston to TDC. Using a burette you would measure the volume of liquid it takes to fill the head volume to the top of the plug hole. Record this number. Take the piston to BDC and now measure the volume used to fill the cylinder to the top of the plug hole. Cylinder Displacement (cubic inches) is the total volume minus the volume at TDC. And FWIW, Compression Ratio is the Cylinder Displacement divided by the Head displacement.
 
Heimedw said:
but if you deck the block you are technically removing space for wich water can take up correct?
Click to expand...

Decking a block only altes compression ratio, not cubic inch displacement.

The bore and stroke determine the cubic inches. You don't even need parts to calculate cubic inches, all you need are the measurements: number of cylinders, bore size and stroke. Those three numbers give you a dead nuts accurate measurement of cubic inches PERIOD. Now throw those parts into a block - doesn't matter if the pistons sit a foot below the deck - the number of cylinders, bore and stroke does not change so the cubic inch displacement remains the same. HOWEVER in that block compression ratio would really suck !!
 
I'll ask a similar question. On the same engine with 3.75 stroke, with nothing else changed, I mill .030 off the top of the piston. What is the new C.I.D. ? It's still the same. Bore & stroke determine it, X the number of cylinders.
 
WileERobby said:
I'll ask a similar question. On the same engine with 3.75 stroke, with nothing else changed, I mill .030 off the top of the piston. What is the new C.I.D. ? It's still the same. Bore & stroke determine it, X the number of cylinders.
Click to expand...

Still a 440 but with different comp ratio
 
Heimedw said:
This may sound like a dumb question. I'm sure some of you are following my 512 build. The machine shop had to deck the block 10 thou and had to machine the top of the pistons for 0 deck. My question is would this effect cubic inch of the engine and is there a way to calculate the change? Also I would assume that when the block was line honed this would also bring the pistons up to the top of the cylinder more. I know that bore and stroke calculates cubic inch but is piston area also a factor? I would assume it does or am I wrong?
Click to expand...

OK now that Milling does NOT affect CID....
What I'd like to know.....
Is AFTER milling the Block "only" 10 thou..... how in the heck did the "Pistons" need machining(milling) to achieve 0 Deck ?

I mean I can understand making sure the Block is "square" by decking to clean it up, and even a .010"/.010" cut is fairly normal to do so, but the Block Milling machine should have shown the Block Deck Heights BEFORE Milling ? so a guy KNOWS where the Block is before removing more/too much from the decks ?
Was the Block Milled excessively sometime previously in it's history that the Pistons were sticking out of their holes above deck ?

Sounds to me like one of those "Oopsie-Daisies" moments.... where somebody goes and Mills a Block too far without checking.... then the Pistons stick outa the holes.... then we gotta Mill the Pistons down to get them back down in the holes..... then we gotta re-balance for the lighter Pistons.... and on and on cluster-**** ?

Line Honing don't do squat to move Pistons UP closer to the deck more than maybe a thou and a half.... unless goober screws that up too and has to start cutting main caps .010"(usually only .003"), in which case it could "maybe" in theory move the Pistons up .005" if .010" were goobered off the Caps ?
 
The block started as a standard bore untouched block. I was told it had a fair bit of pitting on the deck so they took ten thou to make it true and to remove a lot of the pitting. This was done with a c&c machine. The stroker kit I got was from 440 source and I believe that the 512 40 over kit with a dish -24 piston I purchased is based on a stock deck height for 0 deck. Again I'm assuming this I don't know for sure but that's the way it's described on the site. I will have some questions for them this week for sure. They didn't say anything about the line hone bringing the piston up that was my own conclusion. I didn't think it would be much but it would be a little.
 
Heimedw said:
This may sound like a dumb question. I'm sure some of you are following my 512 build. The machine shop had to deck the block 10 thou and had to machine the top of the pistons for 0 deck. My question is would this effect cubic inch of the engine and is there a way to calculate the change? Also I would assume that when the block was line honed this would also bring the pistons up to the top of the cylinder more. I know that bore and stroke calculates cubic inch but is piston area also a factor? I would assume it does or am I wrong?
Click to expand...
Tell us which pistons, and what length rods you started with. Some end up at zero deck, some .017 down, So if you start at zero deck, mill the block .010, then your pistons will be at .010 positive deck. (in a perfect world, which this isn't). There are always variables. So what pistons do you have? The shop could have mistakenly milled too much off the block, so then needed to fly cut the piston tops. Even if you are .010 positive, you can use a .040 head gasket, to get .030 quench. Mopar built a 383 in 68 with a piston slightly positive. Then I suppose some guy came along, put closed chamber heads on the motor, used a .020 gasket, then had .010 quench. Recipe for disaster. So Chrysler stopped doing that. LOL
 
Rod length 6.535 piston-24 dish 0 deck and 1.320 compression height.
 
440Source kits base the compression ratio on 1) head volume and 2) how far the piston is in(or out) of the hole. So if the machinist took the measurements of the deck height like he should have and he was told the CR was based on the piston being a specific distance from the deck he should have been able to compensate the decking with a thicker head gasket. Hell, mine was based on the pistons being .009 in the hole and they ended up .016 above the deck. I used a .051 head gasket.
 
You must log in or register to reply here.

Similar threads

PROSTOCKTOM
FOR SALE Molnar Technologies 4340 Forged Steel 512" 4.25" Stroke 383-400 "B" Block Stroker Crankshaft - New
Replies
2
Views
514
PROSTOCKTOM
PROSTOCKTOM
71airgrabberRR
Looking for a good machine shop in Florida
Replies
3
Views
455
71airgrabberRR
71airgrabberRR
PROSTOCKTOM
  • Locked
FOR SALE Molnar Technologies 4340 Forged Steel 512" 4.25" Stroke 383-400 "B" Block Stroker Crankshaft - New
Replies
0
Views
672
PROSTOCKTOM
PROSTOCKTOM
qkcuda
My new stock stroke 400 build
5 6 7
Replies
128
Views
10K
qkcuda
qkcuda
PROSTOCKTOM
  • Locked
FOR SALE Molnar Technologies 4340 Forged Steel 512" 4.25" Stroke 383-400 "B" Block Stroker Crankshaft - New
Replies
3
Views
1K
PROSTOCKTOM
PROSTOCKTOM
Auto Transport Service
Back
Top