Engine decking issue(help)

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MoparMark91

MoparMark91

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So i have a bit of a issue that was brought to me by the machinist doing my block.
Its a standard 340 block
Had him do boring, line hone mains(due to installing studs) and was going to have hin deck the block to make sure its square and surface is ready for my eddy heads.

Here's the problem-block has never been decked and i bought it off a reputable member. He had the block checked with a machinist for deck height and all corners were above 9.6 or close to it(typical for la motors).

My setup crank stroke÷2+rod length+compression height=9.59

My machinist called me other day tell me block is already at 9.59 and in order to square it up it qould have to go to 9.58.
I look at my options i have as i havent called back yet

A) my machinist didnt measure correctly and i leave the deck how it is(concerned surface wont be smooth enough)

B)Have him deck it to 9.58 as what he says and run thicker gasket maybe cometic

C)Special request just to take off barely anything to ensure smoothness(block could still be out of square though)

Let me know what u guys think i wss planning on stopling by there before i head to work tomorrow
 
Jadaharabi said:
What was the measurement from the first check? All 4 corners.
Click to expand...
LF-9.606
LR-9.601
RF-9.6
RR-9.610
Its almost square already but he says otherwise. The reson i was going to have it decked also was my quench i was concerned about
 
I would put in the crank and the 4 corner pistons (without the rings) and rod assembles and measure the deck heights. Then you will see how much to cut.
 
Jadaharabi said:
I would put in the crank and the 4 corner pistons (without the rings) and rod assembles and measure the deck heights. Then you will see how much to cut.
Click to expand...
Yeah, maybe i can run by with everything tomorow. He said it was in the machine ready to go but wanted to get my opinion/thoughts so i told him i would swing by. Its tough night shift 12 hour shifts lol but im dedicated
 
.010"? could it be because it the mains were line honed? That would have to change the deck height a little wouldn't it?
 
mopfried said:
.010"? could it be because it the mains were line honed? That would have to change the deck height a little wouldn't it?
Click to expand...
You might have something there?! Is that a possibility?
 
MoparMark91 said:
You might have something there?! Is that a possibility?
Click to expand...

Shouldn`t change it that much, unless he went crazy on ur main caps. I`d just bairly square it and gasket accordingly , if it were me .
My 440 block took only .003 to square it to specs -------------
 
MoparMark91 said:
LF-9.606
LR-9.601
RF-9.6
RR-9.610
Its almost square already but he says otherwise. The reson i was going to have it decked also was my quench i was concerned about
Click to expand...

Are these your measurements and you're saying the machinist is getting something else? How are you measuring?
 
RustyRatRod said:
Are these your measurements and you're saying the machinist is getting something else? How are you measuring?
Click to expand...
Those were the machinist measurements from shop where the guy i bought it off of took it too before it came to me and my machinist is saying its already at 9.59. He has done everything else to my block all thats left is decking/resurfacing or not.
 
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MoparMark91 said:
Those were the machinist measurements from shop where the guy i bought it off of took it too before it came to me and my machinist is saying its already at 9.59. He has done everything else to my block all thats left is decking/resurfacing or not.
Click to expand...

Gotchya. Ok, so have you stood there and watched your machinist measure it yet or is that the next step? Cause "somebody's" measuring wrong. If it's really that low, it's very likely been decked before. I've never seen one that low right out of the box. Course, there's always a first.
 
RustyRatRod said:
Gotchya. Ok, so have you stood there and watched your machinist measure it yet or is that the next step? Cause "somebody's" measuring wrong. If it's really that low, it's very likely been decked before. I've never seen one that low right out of the box. Course, there's always a first.
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No i was going to stop by tomorow and see. But from the looks of it, it looks as if it has never been decked. I asked my machinist and he agrees.
 
Post 4 is how you do it. Did you measure the rods? Did you measure the compression height? Did you measure the stroke on every throw?

If not, the deck height number doesn't mean ****. If you measure all those measurements, and they all end up at blue print dimensions, then it means something. They never do.

Put the crank in, and I only use 1 piston, and drop it in all 4 corners and cut the block to the low corner.

Chances are, if you want zero deck, you're going to take a bunch off. If you need a positive deck, like if you are using open chamber heads and you want it right, you'll be taking a bunch off.

My last block took .080ish off to get the piston up .045 past the deck.

You have to measure the corners, or take all the measurements and make them all to blueprint specs.
 
yellow rose said:
Post 4 is how you do it. Did you measure the rods? Did you measure the compression height? Did you measure the stroke on every throw?

If not, the deck height number doesn't mean ****. If you measure all those measurements, and they all end up at blue print dimensions, then it means something. They never do.

Put the crank in, and I only use 1 piston, and drop it in all 4 corners and cut the block to the low corner.

Chances are, if you want zero deck, you're going to take a bunch off. If you need a positive deck, like if you are using open chamber heads and you want it right, you'll be taking a bunch off.

My last block took .080ish off to get the piston up .045 past the deck.

You have to measure the corners, or take all the measurements and make them all to blueprint specs.
Click to expand...
Yeah i plan on bringing my crank and everything in. If he is measuring correctly then ill have to have him pull it out of machine so i can do a mockup
 
yellow rose said:
Post 4 is how you do it. Did you measure the rods? Did you measure the compression height? Did you measure the stroke on every throw?

If not, the deck height number doesn't mean ****. If you measure all those measurements, and they all end up at blue print dimensions, then it means something. They never do.

Put the crank in, and I only use 1 piston, and drop it in all 4 corners and cut the block to the low corner.

Chances are, if you want zero deck, you're going to take a bunch off. If you need a positive deck, like if you are using open chamber heads and you want it right, you'll be taking a bunch off.

My last block took .080ish off to get the piston up .045 past the deck.

You have to measure the corners, or take all the measurements and make them all to blueprint specs.
Click to expand...
if I may, I think yellow rose, when he's saying use one piston, I think he means one piston and rod assembly, with same bearings measured at all four corners. That way you eliminate the variables, otherwise you don't know what you have. All that being said, that just tells you if it is square(provided #1, 2, 7, & 8 crank throws are the same!).
Once you're satisfied, turn your attention to the rod lengths(center to center), to make sure they are consistent, if you haven't already done that. Then you can fiddle with deck heights vs compression ratios.
 
Look, this is REAL easy to do yourself. Get you a 12" dial caliper. If you work on your own stuff, it'll be handy anyway. Stick one end of the caliper on the deck and the other end in the crank bore. Make SURE the end that's on the deck is FLAT and SQUARE to the deck. Close the caliper and take a reading. Then add HALF the crank main bore diameter to your reading. There's your deck height. Do that on all four corners and you can find the answer yourself. It would be easier with two people, so one could hold the deck end of the caliper straight and true to the deck. Calipers have the thin knife edged measuring surface on the ends, but they get wider to give a better surface about 3/4" in. That's the surface you want to use. I measure all of mine before I take them in so I'll know if somebody doesn't know how to read a mic. lol
 
MoparMark91 said:
Yeah exactly but just want to ensure smooth mating surface
Click to expand...

What does the smoothness of the mating surface have to do with the heads??? Unless you are not going to run a head gasket the surface has to be smooth enough for the gasket, not the heads...

A composite gasket can tolerate a rougher surface than a steel head gasket...
 
Thinking about it, take a piston/rod/ bearing and install it in all four corners. Measure. It would be nice to use the longest piston/rod. Install them all in the same cylinder and measure how far in the hole they are. Then use that one. Measure how far it is in the hole it is at each corner. The two variables left are deck height and crank throw. You don’t plan on blue printing the crank so the deck height is what you will need to change. All this is nice but its in the machine.
 
So i just got home from work, when i get up i am going to go talk to him and bring my assembly parts to see if im able to do quick mock up there just to see where im at. As for the surface krazykuda i was unsure of the eddy heads on cast 340 block, just wanted to eliminate anyway for leaking. I am also going head studs also. I will update with what i find and i dont have a 12inch caliper but i will see if i can use my machinists caliper as all i have are a 6 inch. I really appreciate everyones input and thank you guys
 
Two things. I should have pointed out that I only use 1 rod and piston as mentioned above. If you are using stock rods, you really need to measure them. You have no idea how many times they've been rebuilt and that can change the length.

Aftermarket rods are usually dead nuts on. Good Pistons are too.

I also want to mention gasket surface. Back in 1995, I went to a seminar put on by Fel Pro or whoever owned them at the time.

The biggest take away from that was surface finish. The upshot is, regardless of block or head materiel or gasket material, you want a very fine finish. Rough surface finish went away a long time ago. The lie about giving the surface "TEETH" to grab the gasket was wrong.

In fact, if you've ever seen a block or heads come in that went out with a rough surface, the first thing you notice is how much smoother the finish is after run time.

This is because the gaskets main job is to follow the head up and maintain seal on the combustion stroke. It does not matter how many bolts are around the cylinder, how big they are, or even if they are studs.

Every firing cycle lifts the head off the block. And the gasket needs to be able to follow that separation and keep a seal. A rough finish does nothing to help that.

What actually occurs is that during start up and cool down (and even in operation as load changes occur) the head and block are growing and shrinking in all directions. That rough finish is actually worn down by this movement. In fact, as this wear occurs, it not only smooths the head and block surface, it removes materiel from the gasket itself.

And, this causes the the fasteners to lose tension. Now, you start seeing head gasket failures. I can't count how many engines I've disassembled that had head bolts that were loose. And failed gaskets. You get it apart and you see a rough surface that it now relatively smooth.

Gasket surfaces should be smooth with out burnishing.
 
If it's close , leave it alone . sometimes the block decking machine can't correct .001-.003" due to machine tolerances . If your deck is below spec. you can use a thicker head gasket . Mine was .0013" out of square cross corner, THAT'S REALLY GOOD
 
Well I couldn't read any more you all are a little whacked out on how you square deck a block. Our block fixture measures 7" from the main journal bar. You cut the deck using the block fixture. They cost about $7000 dollars from Rottler.

You land a pointer on the deck and then to the 7 inch fixture . add the difference to the 7 inch and zero the DRO This is your deck height Square decking is making both decks exactly the same deck height from one bank to the other using a fixture that holds the block at 45 degrees using the cam tunnel center line. We have some foreign V6 motors that are 60 degrees. My son got Block bars for SB and BB mopar and SB and BB Chevy. he told Dave and I that tonight

When Dave told me about this thread we went to the garage to ask my son. When Dave told him about using the pistons on all 4 corners he about fell off his stool. Square decking is making both decks the same height 45 degree off of the center line of the cam and crank tunnel.

I would like to give precise advise but I don't know machine work like my son. What I can tell you is the little he shows us that we understand is unbelievable. And the tools he has.$$$$$$$. Right now this thread is the joke of the garage. If you don't have the equipment don't give bull **** advise.

To the poster , Take the block to a machine shop. Ask if they have a block fixture and the tooling to install your block for square decking. Tell them to show it to you. If he can't walk out.

This is the a block fixture. Notice no pistons necessary. Just precise tooling that cost a lot of money. That is the correct way. Right Dave?

Probing_Deck_Heights_Block_Squaring.jpg


Probing_Engine_Block_Blueprint_Specs.jpg


Probing_Engine_Block_Deck_Heights.jpg


Engine_Block_Deck_Squaring (1).jpg


Squaring_Deck_Decking_LS1__Block.jpg


Block_Decking_Squaring.jpg


Decking_Engine_Block_Intake_Runner.jpg
 
Oldmanmopar said:
Well I couldn't read any more you all are a little whacked out on how you square deck a block. Our block fixture measures 7" from the main journal bar. You cut the deck using the block fixture. They cost about $7000 dollars from Rottler.

You land a pointer on the deck and then to the 7 inch fixture . add the difference to the 7 inch and zero the DRO This is your deck height Square decking is making both decks exactly the same deck height from one bank to the other using a fixture that holds the block at 45 degrees using the cam tunnel center line. We have some foreign V6 motors that are 60 degrees. My son got Block bars for SB and BB mopar and SB and BB Chevy. he told Dave and I that tonight

When Dave told me about this thread we went to the garage to ask my son. When Dave told him about using the pistons on all 4 corners he about fell off his stool. Square decking is making both decks the same height 45 degree off of the center line of the cam and crank tunnel.

I would like to give precise advise but I don't know machine work like my son. What I can tell you is the little he shows us that we understand is unbelievable. And the tools he has.$$$$$$$. Right now this thread is the joke of the garage. If you don't have the equipment don't give bull **** advise.

To the poster , Take the block to a machine shop. Ask if they have a block fixture and the tooling to install your block for square decking. Tell them to show it to you. If he can't walk out.

This is the a block fixture. Notice no pistons necessary. Just precise tooling that cost a lot of money. That is the correct way. Right Dave?

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well, duh! Why doesn't he just farm the work out to Penske? Very few forum members have a $100K tool with $50K more in tooling. Truth be known, probably not that many automotive machine shops have that kind of tooling. We are suggesting low-buck, real-world solutions. Hobbyists and small machine shops have had to get by doing more with less for years.
If you think everybody else is an idiot because they don't take their engines to your son, you need to get a grip and take some reality pills.
 
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