LB7: head gasket info

x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
7,535
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Lexington, Ky
Only set I like supplying in my kits. I have sold a couple of the Lml but only for a 100% stock truck. I will not stock them like others never felt safe with the new ones.

If it ain't broke, don't fix it. Especially when the good ones aren't crazy price. I'd buy what Henry's sellin there!
 

JDT4430

Member
Jul 29, 2014
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Well the motor had one A and one B gasket in it. So im thinking now that i need to try ad return the gaskets i have and get a set of grade C gaskets. What do you guys think. Also think im gonna break down and get the manual for the duramax to get more info on this.
 

JDT4430

Member
Jul 29, 2014
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Ok i've been reading up on the head gasket thickness and everything i have read says to check the protrusion of the pistons to determine the gasket thickness. If i have not done anything woth the block or the pistons and it had an a amd b hasket in it wouldnt the two grade Bs i have work. I had head work done so yes if they didnt recess the valves they may be a bit closer to the piston but will this even be an issue meaning are the valves even ever fully open when the piston is all the way up? Really want to get this thing together this weekend if at all possiable but do not want to make a huge mistake.
 

JDT4430

Member
Jul 29, 2014
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Not sure if this has been posted here or not, but Henry posted all the head gasket info here:
http://www.duramaxdiesels.com/forum/showthread.php?t=6148

Hope it helps

Yes i have read all that info more than once. For one im not sure exactly how to measure the protrusion of the piston. Im guessing you need a mic with a wide enough tip that you can set the zero to the block then run the piston up and read the protrusion i can get my hands on a mic but it just has a small point.

But still what i cant wrap my head around is that all the info you read about selecting the proper gasket just talks about the protrusion of the piston. So if i havent done any thing that will change that why woundnt the same grade gaskets work. Or does having the heads redecked make the valves to close as they are opening and closing.

Not trying to be a pain in the ass cause i know yall are all thinking just spend the money amd get grade C's and dont worry about it and I most likley will do that but im still curious. If somebody wants to explain this stuff to me over the phone instead of typing just pm me for my phone number or send me yours and we can talk about it. Thanks guys Im just trying to learn.
 

Mile_high

The Mad Hatter
Oct 31, 2009
702
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Denver, Colorado
Yes i have read all that info more than once. For one im not sure exactly how to measure the protrusion of the piston. Im guessing you need a mic with a wide enough tip that you can set the zero to the block then run the piston up and read the protrusion i can get my hands on a mic but it just has a small point.

I used a depth micrometer.

But still what i cant wrap my head around is that all the info you read about selecting the proper gasket just talks about the protrusion of the piston. So if i havent done any thing that will change that why woundnt the same grade gaskets work. Or does having the heads redecked make the valves to close as they are opening and closing.

If the heads were surfaced, but the valves were not touched, the valves were moved towards the block by the depth of the cut on the head. If the valves aren't moved, the head gasket thickness must increase by the depth of the cut on the head.
 

JDT4430

Member
Jul 29, 2014
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Ok so the clearance between the valves and the piston are very close also. I just was having a hard time imagining that the tolarnces would be that close so that pretty much answers my question as to weather order new gaskets or not. I guess if i had a way of measureing protrusuion the B's could still work depending on were the protrusion falls in the range. Also I need to call the machine shop and see if the valve seats were cut any I guess.
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
15,607
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Mid Michigan
Yes i have read all that info more than once. For one im not sure exactly how to measure the protrusion of the piston. Im guessing you need a mic with a wide enough tip that you can set the zero to the block then run the piston up and read the protrusion i can get my hands on a mic but it just has a small point.

But still what i cant wrap my head around is that all the info you read about selecting the proper gasket just talks about the protrusion of the piston. So if i havent done any thing that will change that why woundnt the same grade gaskets work. Or does having the heads redecked make the valves to close as they are opening and closing.

Not trying to be a pain in the ass cause i know yall are all thinking just spend the money amd get grade C's and dont worry about it and I most likley will do that but im still curious. If somebody wants to explain this stuff to me over the phone instead of typing just pm me for my phone number or send me yours and we can talk about it. Thanks guys Im just trying to learn.

Harbor Freight has the micrometer and the magnetic base you need. Works very well. Zero the mic to the block deck surface nearest the piston, then carefully turn the mic over to the top of the piston, and read the change as you rotate the crank. Simple.

If nothing on your engine had changed, and it came with A & B gaskets in the first place, then just swap the new B's in and be done. But if you've had the heads decked, then you've changed the p-v clearances and you should just use C's.

Dmax headgaskets arent a huge expense any more since the LML sets have come out. Henry carries them.
 

JDT4430

Member
Jul 29, 2014
75
0
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If nothing on your engine had changed, and it came with A & B gaskets in the first place, then just swap the new B's in and be done. But if you've had the heads decked, then you've changed the p-v clearances and you should just use C's.

Ok thats what i was looking for. Was not sure if the change in the p-v clearance would be enough to effect the gasket selection so since you guys are aaying that it does effect the selection i will order new gaskets from henry and hope like hell the machine shop will give me money back for the ones he ordered.

Thanks for clearing this up for me.
 

EDP

<<<< Miss The Ol Girl
standard arp's

Bump up in stud Ksi rating with the boost you are running.

We have ran both what is called the LML style and the all black Mahle style and didnt really see to many issues or concerns but have since gone away from both and now use a custom 5 layer built for us. They are kind of expensive but we have not scene any issues to date as well they are re usable which is nice for the competition scene.