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Old 04-10-2003, 01:58 PM
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Post zero deck the block

I was reading a past post and a suggestion was to zero deck the block.

What does this mean?
Does the machine shop do this?
What is the benefit?

Thanks

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Old 04-10-2003, 02:10 PM
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Zero decking the block IS machining the surface of the block ( where the heads meet the block ) to have zero clearance with the piston at top dead center. Or in commom terms...... the piston is the exact same height as the block when the piston is all the way up.

Do this before you bore the block.

A lot of engine builders do this to increase compression and to get the distance between the bottom of the head and the top of the piston to be a certain thickness. A lot of engine builders want .039 to about .048 distance ( this includes the head gasket thickness ).

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Old 04-10-2003, 03:37 PM
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I'm not sure how you could do it before you bore, since you haven't checked the piston height with the new pistons. Since most modern boring bars set up off the mains it isn't neccesary to surface the block first.
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Old 04-10-2003, 04:02 PM
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I would have to agree with Woods. It would be hard to tell for sure where you want the deck before boreing the block for the pistons that you are using. Boreing and decking should be set-up based on the mains.
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Old 04-10-2003, 05:53 PM
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It is very easy.

The crankshaft and the rod lenght would stay the same. Thr only difference is the pistons. You measure the the difference between the piston pin/top of the piston and adjust the deck accordingly. I stay about .005 away from zero deck.

I always bore my engines with a deck plate to simulate the heads being on. If you deck the block AFTER you have bored the block...... you would not have a round hole.....just like boring a engine without plates.

I try to simulate everything I can when doing engine machining. The mains are torqued, the plates are on....torqued using the same brand and thickness head gasket. I pump 200 degree water thru the block for 1 hour prior to boring.


Just me.........


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Old 04-10-2003, 06:10 PM
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I will add to the conversation about decking the block before you bore it, and I say that it depends upon what type of boring equipment you are using. Case in point, if you are using a portable boring bar, the machine sits on the deck of the block, and "cat-paws" are used to center the boring bar in the cylinder. What can happen, and has happened to me before is that if you "square-deck" or deck the block parallel and perpendicular like it is when you blueprint it, you sometimes really change the deck angle, and, if you are using a portable boring bar, it becomes difficult {or impossible to clean up the bores with a minimum cut {like .030}, but if you are using a machine that references off of the pan rails (like a Rottler} then you won't have that problem. So, I would bore before you deck with portable equipment.
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Old 04-10-2003, 06:57 PM
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My block was bored with torque plates first. I then mocked up the crank, rods and pistons and measured how far in the hole they were.

One side was pretty even front to back and I had them take of .025. The other side had a .004 variance front to back. They milled the straight side first, then flipped it 90 and did the other. Decked and squared.

I'm just completing final assembly and each piston is .004 in the hole. I'll be using a .039 head gasket and 58cc heads. I expect approx 10.5:1 CR.
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Old 04-11-2003, 04:38 AM
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[quote]Originally posted by mstngjoe:
<strong>My block was bored with torque plates first. </strong><hr></blockquote>

Put the torque plates back on and check the cylinder walls.........

I believe you will find that they are not perfectly round NOW. You changed the block deck surface. The one with the .004 variance should be off more than the side than was level.....


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Old 04-11-2003, 05:56 AM
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[quote]Originally posted by Deuce Roadster:
<strong>

Put the torque plates back on and check the cylinder walls.........

I believe you will find that they are not perfectly round NOW. You changed the block deck surface. The one with the .004 variance should be off more than the side than was level.....


.</strong><hr></blockquote>

I don't know you or what your experience is.

The machine work on my block was done by a professional shop with a top reputation for performance building. They have been in business for almost 50 years. My family has been doing business with them for more than 25 years. Never a problem in all that time. I completely trust their judgement.

Thanks for your opinion.
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Old 04-11-2003, 08:26 AM
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[quote]Originally posted by mstngjoe:
<strong>

Never a problem in all that time.

Thanks for your opinion.</strong><hr></blockquote>

And you will not have a problem now, but the hole is NOT as round as it would have been had you not decked the block after boring and honing it to finish size.

You now have a squared deck block that was in all effect bored and honed without a torque plate.
That will not cause a real problem......it was done for years before torque plates became acceptable and used by 'open to the public' machine shops. Torque plates were a well guarded secret by top engine builders for a long time.

I was a tool and die maker for Holman-Moody in Charlotte NC and then a auto machinist for many years.


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Old 04-11-2003, 02:47 PM
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I won't dispute the possibility that I have a less than perfect block based on your evaluation.

And I have the utmost respect for professional machinists. Particularily one with your credentials.

The variances you describe are negligible/acceptable in my particular application. Were I building a pro-stock motor, prepping the block by your method would be a better alternative.

Again, thanks for your opinion and input.

And congratulations on having the opportunity to work for a company with such a rich tradition and history of performance.
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Old 04-11-2003, 05:31 PM
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Not a problem.

Was not trying to be difficult.

I worked there many years ago. Their glory days had been earlier (64 to 70) than my employment and I contributed nothing to the glory.


We took a block in and located it in a jig. The jig had a pin that located the crankshaft centerline between centers. You looked at the camshaft bore and made sure that casting shift was not too bad. We would locate the center of the cam bore and lock everything secure. Then the top of the block is machined to spec (parallel to the crank centerline). Then rotate the block 45 degrees and machine the deck to spec. Then rotate the block back 90 degrees and machine the deck to spec. Most factory OEM block need atleast .020 or more to be down to spec. THEN the block was ready to be bored to it correct overbored size.

Crankshaft throws and rod lenghts vary. This can vary the distance a piston is down in the cylinder wall by as much as .005

We also sized the rods for correct bearing size and corrected the lenght (or made them longer) by bushing the little end.


ENOUGH of my memories........


.
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Old 02-13-2012, 03:41 PM
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Bogie,
I do believe the heads are swirl ports. There the 193's. I will be putting a set of aluminum heads on it, not just right yet. Pistons are Keith Black 135 pistons says they are 18cc volume D- Cup. Am i going to be okay?
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