Mighty Whitey

ok, so a stock crank is a 3.48" stroke, a stock rod is 5.7" and a stock piston has a compression height of 1.55", and the stock block has a 9.025" deck height. correct?

we all obviously know that: stroke/2 (1.74") + rod length (5.7") + compression height (1.55")= deck height (I suppose that would be the term?)
which is 8.99"
9.025"- 8.99"= .035"

so a stock piston sits roughly .035" in the whole, correct?

now, if you substitute 5.7" rods for 6.0" rods, and 1.55"CH pistons for 1.25"CH pistons, you get the same results.

as entertaining as decking the block .035" is, I would much rather see a piston take up the slack to bring a zero-deck height. decking the block will pose cylinder head-to-intake port alignment problems I would imagine.

do any companies offer even a 1.28" or 1.58" CH piston? decking the block .005" isn't bad, and would probably be all that would be required to make a block square. along with not causing too big of a problem with intake port alignment.

I would imagine a zero-deck motor, while not only being higher in compression, but would also make for a more efficient motor, by reducing the quench area between the cylinder head and piston, and there fore yield more power, correct?

if the gains are well worth the extra money, I would have no problem paying $600 or $700 bucks for a set of JE's, as opposed to the Speed-pro units I intend on running. the more power you unleash through blue-printing, the less power you have to compensate for, with more cam/rpm/boost/nitrous/etc.

speed_demon24

iTrader: (6)

You can get the intake manifold milled so the ports line up after you zero deck the block.

Mighty Whitey

I know you CAN mill the intake to work. what I was basically trying to see is if a piston manufacture makes piston to compensate for the negative deck-height that the factory piston has, without decking the block, if possible.

seawolf06

iTrader: (8)

Your math is wrong. The stock pistons are approx. .025" in the whole. You added one tenth instead of one thousandth to get .035" where you should have .026".

There are two ways to achieve "zero deck" that I know of. The first is to "square deck" the block where the machine shop simply measures 9" from the center of the crank and then mills to that point. This doesn't take into account what rod/piston combo you are using. The second method requires assembling your block with at least two pistons and rods on the crank. Then they'll mill each side to where the piston reaches TDC. The most accurate way would be to use all eight pistons and rods and then mark the highest one. That way there's no chance of the piston hitting the valve.

These are the only two methods I know of although I'm sure there are more.

Zero decking the block allows you to have a broader choice of head gaskets to get the CR and quench you need. The less you mill it, the more likely you will be to require a custom gasket to hit your targets.

FASTFATBOY

iTrader: (23)

The correct way is to use the rotating assembly you will run in the engine. Put the crank in on two old bearings. Use one assembled rod/piston, with an old bearing, install it in each of the 4 corners of the block, on the crank. find TDC, measure how far the piston is in the hole on each of the 4 corners and write it on the block. Have the block square and zero decked. Mine was different on all 4 corners as to how far it was in the hole.

Zero decking is not enough to have the intake re-faced, it will seal fine.

David

1989GTA

Another method is to offset grind the crankshaft. If you go .020" on the rod bearings you can almost get .020" on the stroke. A local crankshaft grinder wants $200 to do it.

seawolf06

iTrader: (8)

There aren't any offset timing sets for the LT1, though.

If I'm taking that much off the block, I would at least get the intake ported to match the heads. I had to get mine milled, but I don't know how much the heads were milled.

fireman

This is true, I am zero decked and bolted my intake up fine.

FASTFATBOY

iTrader: (23)

Why do you need and offset timing set?? Crank to cam relationship is not changing. As a matter of fact there are timing sets for when you line bore a block to make the chain tighter. If you offset grind the crank, only the rod journals are being messed with.


.030 is not going to mis-align heads and intake. Enough to matter anyway.


David

Mighty Whitey

I fail to see where my math is wrong
block deck height is 9.025"
3.48/2= 1.74 + 5.7= 7.44
Compression height is 1.55 stock, correct?
if so 7.44 + 1.55= 8.99
9.025 - 8.99 = .035?

that's how I got the .035" in the hole. or is CH of the piston 1.56 stock?

anyway. I know the most common way is to deck the block, is this also the best way to do so?

a reputable engine builder in my area said there is up to .030" difference in stroke from journal to journal on a stock GM crank. is this true? *this engine builder also claims eagle cast cranks are better than stock, and that an eagle SIR rod is better than a Scat pro-comp rod* so his legitimacy may be in question.

I've thought about offset grinding the crank, how is crankshaft strength compromised?

I know the intake will bolt to the heads no problem, but decking the block (or even the heads for that matter) would lower the intake runner in relation to the intake manifold- the roof would be too low, and the floor would be as well) all of this seems fine, but how would you know what to port? the gasket surfaces have not been touched, so they will effectively still line up as before, but there relationship onced bolted to the block will not be.

IDK, maybe I'm just making too much out of nothing. I'm not looking to change my setup from what it is now- 380rwhp is fine by me. using my stock heads with manley valves (why not, right?) and the same cam/rockers I have now, I beleive I can put 400+ to the ground by just reworking the bottom end, making it a more efficient motor.

seawolf06

iTrader: (8)

The "square" height is supposed to be 9.000" IIRC. Of course there are deviations due to tolerances and such, but LT1 pistons are about .025" in the hole.

I must have misunderstood you, fastfatboy.

Mighty Whitey

I'm not sure how all that goes, but isn't the offset amount only 1/2 that of what you decrease the deck height by? being that it's a 45* included angle?

man, I knew I shoulda paid attention more in math class when they started talking about sin cosin and tangeht (or how ever you spell it! lol)

anyway, is CH of a stock piston 1.55" or 1.56"?

streetwarrior96

my deck height is at 9.000 -9.005... I am using the stock .038 gasket can I get the one from the impala in increase my CR.

current CR 10.5:1

Mighty Whitey

a 9.005" deck height with a impala gasket (.029") would give a .034" quench, pretty much optimal, correct?

or would it be too close for comfort to run a true 9.000" deck, and run the .029" impala gasket?

I've heard not to go less than .030", so you can account for rod bearing oil clearance, rods stretch/growth (which would be more for a 6.000" rod, wouldn't it?) piston rock, and a minor amount of piston growth.

but with quality machine work, would .001" make that big of a deal?

TravisA

iTrader: (4)

Hmmm...I believe I heard the same story....If we're talking about the same guy,h e also said that I couldn't run over 11.5:1 compression on the street with an LT1...

Lets see, he also said not to pay attention to what Mahle said on there Piston to wall clearance and to open my top ring up to .060 and that he has bored LT1's out 80 over with no problems.

speed_demon24

iTrader: (6)

Find a new engine builder ASAP.

FASTFATBOY

iTrader: (23)

The square deck height is NOT a common number, I.E. the same for every block. All rotating assemblies are different...MOST zero deck small blocks ARE near 9.0. This is THE reason you use THE rotating assembly you are going to run in the block for the mockup to measure the deck height.


David

dhdenney

iTrader: (53)

Well if it were me and I ain't no pro I would go the custom piston route. I am pretty sure some of the manufacturers can do a custom set for a reasonable price. I would mill the deck as little as possible and then fill the gap with a custom piston set. By my calculations on my LS1 motor, I will only have to mill the block less than .005".

Vicious95Z28

iTrader: (1)

Your math is wrong because 8.99 to 9.025 is .026 not .035

Mighty Whitey

dude, how the **** is my math wrong? I've checked FIVE calculators, including the one in my head, and every one of them says:9.025 MINUS 8.99 equals .035

ok, lets think about this 8.99, add .010, or .01 if it's easier. .01 plus .99 equals 1.00, add that to 8 and you get? 9.00, add the remainding .025 to your 9 and you get 9.025.

so adding .010 to 8.99 gets you 9, and .025 to 9 gets you 9.025
.010 plus .025 EQUALS .035

I think you're forgeting that 9.025 minus .026 equals 8.999, not 8.99. that's .009 (nine-thousandths) which, coincidentally ADDED to .026, equals .035

Jesus people, how tough is simple math? I know i'm from eastern kentucky, where all we know how to do is cut hay, and mine coal, but give me a damn break!

TravisA- yeah, this George Carlin look-a-like told me all of this.. I was thinking he was off his rocker a little bit when he told me all that stuff. I'm gonna see how shumway's motor turns out, if it does good, and lasts, I'll probably hit up kenny gurlock (sp?) for some machine work and parts. josh says he's pretty reasonable on everything.