Decking a block?
06-29-2005, 09:05 PM
#17
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Re: Decking a block?
Something to familiarize yourself with is the term Ra...just say it "R" - "A" A value assigned to show the average hight differences between the peaks on a machined surface...basically "how rough". Ra value is important for head gasket seal, very much so with MLS gaskets, you need to have the same value on the block deck and the head so that as the material "grows" it doesn't kill the gasket... For example todays aluminum heads come from the factory with an Ra value of 14-18, older stuff was in the 40-60 range....the type of cutter and the speed of the feed determines the final finish quality. We have CBN(Cubic Boron Nitrate) for use with cast iron and PCD(diamond) for aluminum....on aluminum heads with the diamond I can get Ra values of 3. For cylinder bores, the number to look for is ~15
06-30-2005, 12:25 AM
#18
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Re: Decking a block?
I think I read something about MLS gaskets and Ra in a magazine not too long ago.
Is it possible to convert from stone grit to Ra? Like what's the approximate Ra of a cylinder honed with a 500 stone?
Is it possible to convert from stone grit to Ra? Like what's the approximate Ra of a cylinder honed with a 500 stone?
06-30-2005, 08:27 AM
#19
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Re: Decking a block?
Originally Posted by TheNovaMan
I think I read something about MLS gaskets and Ra in a magazine not too long ago.
Is it possible to convert from stone grit to Ra? Like what's the approximate Ra of a cylinder honed with a 500 stone?
Is it possible to convert from stone grit to Ra? Like what's the approximate Ra of a cylinder honed with a 500 stone?
Your shop should have a chart to tell them and most don't measure it they just go by their chart and pick the proper stone or cutter to get the desired RA.
Last edited by 1racerdude; 07-11-2005 at 07:24 PM.
07-11-2005, 07:26 PM
#22
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Re: Decking a block?
Originally Posted by MachinistOne
For cylinder bores, the number to look for is ~15
Originally Posted by TheNovaMan
I think I read something about MLS gaskets and Ra in a magazine not too long ago.
Is it possible to convert from stone grit to Ra? Like what's the approximate Ra of a cylinder honed with a 500 stone?
Is it possible to convert from stone grit to Ra? Like what's the approximate Ra of a cylinder honed with a 500 stone?
Good thread on this.... (BTW it's a good place to learn over there, not really to ask questions about LT1's IMHO)
http://speedtalk.com/forum/viewtopic.php?t=1264
Basically the only way to get a surface finish is to measure it... kinda like degreeing a cam, only way to know it's right is to measure it reguardless of where it was ground or if it's "dot to dot" one of my many pet peeves.
Bret
07-11-2005, 08:17 PM
#23
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Re: Decking a block?
07-18-2005, 11:24 PM
#25
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Re: Decking a block?
Originally Posted by SStrokerAce
Good article...
the old man taught me, which I think is the easiest way to think of it....
Ra is the surface and tops of the plateau
Rz is the depth of the valleys
Bret
the old man taught me, which I think is the easiest way to think of it....
Ra is the surface and tops of the plateau
Rz is the depth of the valleys
Bret
07-20-2005, 06:32 PM
#26
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Re: Decking a block?
Originally Posted by arnie
A good (competent) shop that does engine machining does not need the short block partially reassembled to determine deck height.
The dimensioning/setup is done using the crank centerline for reference. Same reference/setup point as when boring is done. The shop just needs to know what deck clearance you desire. The rest is simple math (stroke/rod length, and compression height of piston).
To give me insight into how far out of square the block is, I check it before I take it to the machine shop, using a piston of the present cylinder dia.
Where I come from, that (squaring up AND going to a predetemined distance) is exactly what decking is. It is understood, the block is to be square, may as well know where you want to stop.
As explained above, you know going in, how far out of square the block is beforehand, so you will know the max height of block achieveable with clean up cut. This allows you to detemine (beforehand) what you've got after squaring up the block. Machining accuracy is there (+-.001"). 
Works/good enuf for me.
The dimensioning/setup is done using the crank centerline for reference. Same reference/setup point as when boring is done. The shop just needs to know what deck clearance you desire. The rest is simple math (stroke/rod length, and compression height of piston).
To give me insight into how far out of square the block is, I check it before I take it to the machine shop, using a piston of the present cylinder dia.
Where I come from, that (squaring up AND going to a predetemined distance) is exactly what decking is. It is understood, the block is to be square, may as well know where you want to stop.
As explained above, you know going in, how far out of square the block is beforehand, so you will know the max height of block achieveable with clean up cut. This allows you to detemine (beforehand) what you've got after squaring up the block. Machining accuracy is there (+-.001"). Works/good enuf for me.It's easier for me to mock it up on all four corners than depend on somebody to measure cause he don't know the length of the rods and pistons.
measureing off the crank center line has always been the way to do it,thats what ya do when ya check all four coners with the same piston and rod assy,and crank.
The only thing that measuring it tells ya is how to get both sides equal not to what height
Decking and square deck and equal deck are not the same. If ya just deck a block means all ya want to do is make sure it's flat.Square decking and equal decking is to make sure its the same height front to rear and side to side,
Use your head Arnie most engine builders know what decking is .
Last edited by 1racerdude; 07-20-2005 at 09:41 PM.
07-20-2005, 07:00 PM
#27
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Re: Decking a block?
[QUOTE=arnie]
Ya know,I have a sign in my shop that reads"I don't care how they do it up north" and it is true.
I am well aware of how to deck a block.
Originally Posted by 1racerdude
It's easier for me to mock it up on all four corners than depend on somebody to measure cause he don't know the length of the rods and pistons./QUOTE]The shop isn't measuring anything. It is in the setup in the fixture.Larry, appears I didn't explain myself well, or you misunderstood me. The machining is done off the crank centerline. The measuring (by me) is is done with piston/rod mockup. The "daaaa" tells me I was misunderstood. Tells me at what height the clean up cut will be.Larry, not stating your definition is incorrect. I merely stated stated, ISMW, when I tell the guy I wanted the block decked. He will ask me to what height. Calm down Larry.
Tells me at what height the clean up cut will be.Larry, not stating your definition is incorrect. I merely stated stated, ISMW, when I tell the guy I wanted the block decked. He will ask me to what height. Calm down Larry.Ya know,I have a sign in my shop that reads"I don't care how they do it up north" and it is true.
I am well aware of how to deck a block.
07-20-2005, 07:03 PM
#28
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Re: Decking a block?
What do ya say I just delete the whole goddamn post, Larry?
Happy now, Larry? You know what you can do with your "daaaas".
Isn't me doing things the hard way, geez.
Happy now, Larry? You know what you can do with your "daaaas".
Isn't me doing things the hard way, geez.
Last edited by arnie; 07-20-2005 at 07:09 PM.
07-20-2005, 07:55 PM
#29
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Re: Decking a block?
Ive just started taking a few machining classes at school.
We have a block mill with a CBN bit in it. Basically the mains sit on a bar and then its tightened down through the cam bore. and then level it all off.
Random Questions...
If you assemble a block and find you need .005 for 0 deck, I guess you could rub off the machine and cut your .005. What happens if the core has shifted and you have .005 in number 8 and .001 in number 2? Do you cut the block at an angle?
We have a block mill with a CBN bit in it. Basically the mains sit on a bar and then its tightened down through the cam bore. and then level it all off.
Random Questions...
If you assemble a block and find you need .005 for 0 deck, I guess you could rub off the machine and cut your .005. What happens if the core has shifted and you have .005 in number 8 and .001 in number 2? Do you cut the block at an angle?
07-20-2005, 08:27 PM
#30
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Re: Decking a block?
For just standard decking, I use a large machinist's level and cut flat off the original surface. For precision stuff, you setup a dial indicator and can use that to adjust how much is cut from each end and side to side.