Do I need a thicker head gasket or not?

[flyinwrenches]

So, the machine shop I have my engine and heads at said they took 5 or 7 thousands off when resurfacing the head. They said that I just needed to get a factory thickness gasket...I dont know about that. I don't think that they do many duramax engines. I wanted them to cut a key seat in the cam and crank as well. They said they had never cut one in a cam. They are working on figuring that out. They do build a lot of really mean gas engines for racing. I asked them if they would machine a diesel, and they said they do it all the time...now, I wonder. I know they did good on the crank, line bore, cam bearings, wrist pin bushings, and cylinder bore, but I am a little nervous now on the cam and heads. Anyways, I wish they would have took off a clean 10 thousands like they should have and then I could just get the next step up gasket. What should I do now? Is factory thickness really fine or not?

 

[flyinwrenches]

To elaborate a little further. I need to figure out if the clearances fall into spec for assembly. I have a deck bridge to measure piston protrusion. So, I am just thinking about taking the 7 thousands that they took off and just add that to whatever measurement I get on the piston protrusion to determine my headgasket thickness I need. Am I thinking about that correctly?

 

[Chevy1925]

You dont know enough to be second guessing them. Machining a key way into the cam requires special way of holding the cam without damaging it. They can most likely do it but not every diesel engine requires this

Next, your heads are flat. They do not have combustion chambers. Taking material off the head on the cylinder side does nothing for choosing what head gasket you need. Thats strictly based on piston protrusion and what kind of head to piston clearance you want. Decking the block and getting pistons already cut .005 or .010 will affect your piston protrusion and piston to head clearance.

The fact they only took .005 to .007 off did you a favor in putting that ybridge back in and possibly needing valves recessed into the head

 

[flyinwrenches]

You dont know enough to be second guessing them. Machining a key way into the cam requires special way of holding the cam without damaging it. They can most likely do it but not every diesel engine requires this

Next, your heads are flat. They do not have combustion chambers. Taking material off the head on the cylinder side does nothing for choosing what head gasket you need. Thats strictly based on piston protrusion and what kind of head to piston clearance you want. Decking the block and getting pistons already cut .005 or .010 will affect your piston protrusion and piston to head clearance.

The fact they only took .005 to .007 off did you a favor in putting that ybridge back in and possibly needing valves recessed into the head

Ok, understood. I shouldn't be judging them then. I didn't know that about the camshaft. I am getting it keywayed because the whole reason the engine went down initially was a failed cam pin.
The valve clearance was what I was wondering about. I know that measuring protrusion is the super critical factor and if I understood you right, then they are correct in saying that taking a tiny bit off the head mating surface doesn't really matter. Right?
Also, I wasn't thinking about the v block heads. Your absolutely right that they did me a favor. That y bridge would be an issue if they took off too much. I wasn't thinking about that, I was hung up on thinking about valve clearance.

 

[flyinwrenches]

My thinking is, by machining .007 off, then your essentially bringing the valve down .007 closer to the piston at tdc. So, to account for this, I was going to measure piston protrusion, and take the measurement I get, and just add on .007 to it. Then, pick the head gasket from there. Is that wrong?
And maybe I am just splitting hairs on it. I mean .007 off the head is a very tiny amount. Maybe thats why it don't matter.
Edit- Nevermind, that won't work. If you add the .007 to the piston protrusion, then you would open the quench space up by .007 and affect the burn. It would have to be done by receding the valves in by .007. Right?

 

[flyinwrenches]

Forget it guys, I am overthinking the crap out of this. I was wanting things dead on precisely. But, I am just going to measure the protrusion and get the gasket from there. The valve clearance will have to be addressed in the head by the valve recess measurement. If you try to change it with a gasket, then it don't work. As stated above, it changes the quench space measurement...which I wasn't thinking of before I posted this. It should be fine I think.

 

[flyinwrenches]

Sorry, this is just bugging the crap out of me. I can't let it go. The rebuilding info I have says that the maximum warpage for a head should not exceed .0039. If it exceeds this, then replace the head. That means you could only cut .004 off the head before you have an issue. They cut .007 off. I am really nervous that they ruined the heads. Is this acceptable?

 

[flyinwrenches]

Here is the info I have am referring to...
"Measure the cylinder head for warpage with a straight edge and a feeler gauge. A cylinder head block deck with warpage in excess of 0.1 mm (0.0039 in) must be replaced"

Edit-Oh, and by the way, they didn't recess the valve seats any. They are still at the factory depth. The heads I took them were off a low milage running engine. I payed pretty good money to get them. They weren't my old higher milage heads.

 

[flyinwrenches]

I guess the best course of action is to just bring the information I have to the machine shop and discuss it with them. I just really dislike these guys thats doing the work though. They told me that they would not warranty the build if I did the assembly. So, I told them go ahead and build it in house then. So, then they told me that they did not feel comfortable assembling it because I bought the parts and didn't order through them. Mind you, I ordered mahle performance pistons. Not cheap crap. The rod bearings and main bearings they ordered because of this reason of no warranty except on in house parts. I payed more through them and they were king bearings. Same for the wrist pin bushings and cam bearings. The gasket set is mahle. I just don't understand them. The only thing I bought was the pistons and gasket set. That's it. I can build it just fine, since I do diesel work on equipment and big rigs, but the duramax is kind of newish to me. I have did a lot of work to them, but my knowledge level on them pales in comparison to you guys. Anyways, the shop seems fishy. I talked with a couple other diesel mechanics and they confirmed my worries by telling me they didnt know diesels and screwed them up. One big truck mechanic said they ruined his customers block and decked it crooked, then refused to compensate him anything back. I wish I knew all this before using them. I was using someone else before, but these guys are a lot cheaper and now I am really nervous. I have had the engine over there 4 months or so at this point. That is the backstory as to why I am nervous about these guys and their work. Anyways, we will see I guess. I guess there is nothing I can do about any of it until I get my engine parts back next week and take some measurements.

 

[ikeG]

Your heads will be fine. Ive taken double digits(.010 +) off without issue before. There is a spec for valve recession and piston protrusion. Measure those and decide on gasket thickness

Sent from my SM-G990U2 using Tapatalk

 

[flyinwrenches]

Your heads will be fine. Ive taken double digits(.010 +) off without issue before. There is a spec for valve recession and piston protrusion. Measure those and decide on gasket thickness

Sent from my SM-G990U2 using Tapatalk

That is great to hear, when I get my parts back, I will take all the measurements and compare them to my info I have then. Thank you so much! That eases my mind on it. I get caught up on specs and trying to be perfect. I have OCD and if something does match spec information, then I literally get anxiety from it and can't use the part. This eases my mind.

 

[Bdsankey]

Look at your cylinder head, it is flat. As long as valve recession is maintained (there's a spec for it) then you have zero issue with it. You can take more that what they did off and it's perfectly fine as long as valve recession spec is maintained.

Machining the head has no effect on compression on these engines.


Piston protrusion is used to determine gasket thickness and should be checked (as it appears they did). If they're telling you that you need an OEM thickness gasket, I would listen to them unless you're going to buy the tools to measure and check this yourself.

 

[flyinwrenches]

Piston protrusion is used to determine gasket thickness and should be checked (as it appears they did). If they're telling you that you need an OEM thickness gasket, I would listen to them unless you're going to buy the tools to measure and check this yourself.

They didn't measure anything. They refuse to assemble any of it, as stated above. There is no way for them to measure piston protrusion without the pistons in it. They are just guessing on it. I understand the heads
gasket thickness dont affect compression, but it does affect valve clearance. I was thinking strictly about valve clearance, but I already posted above and changed my mind. A person would open the quench space up too much if they weren't careful.
They didnt recess the valves in the head any and I seriously doubt they measured valve recession depth.
I have all the tools to measure everything already.

This part you said....
"You can take more that what they did off and it's perfectly fine as long as valve recession spec is maintained."

Thats is the part thats giving me anxiety over the deal. Because there is a spec in my information that says .004 is the maximum allowable depth to cut material off the head. A person could cut more, but then they would have to recess the valve seats...according to what I have. Since they took .007 and didnt recess the valves, then it falls .003 out of spec. As I stated above, I literally get anxiety over parts that fall outside of spec. Even by .001. I just can't use them unless they fit the right specification. I have mild OCD and it sucks. I won't know until I get all the parts here and measure everything though.

 

[gmduramax]

Just throw the heads away and buy new ones then

 

[Bdsankey]

They didn't measure anything. They refuse to assemble any of it, as stated above. There is no way for them to measure piston protrusion without the pistons in it. They are just guessing on it. I understand the heads
gasket thickness dont affect compression, but it does affect valve clearance. I was thinking strictly about valve clearance, but I already posted above and changed my mind. A person would open the quench space up too much if they weren't careful.
They didnt recess the valves in the head any and I seriously doubt they measured valve recession depth.
I have all the tools to measure everything already.

This part you said....
"You can take more that what they did off and it's perfectly fine as long as valve recession spec is maintained."

Thats is the part thats giving me anxiety over the deal. Because there is a spec in my information that says .004 is the maximum allowable depth to cut material off the head. A person could cut more, but then they would have to recess the valve seats...according to what I have. Since they took .007 and didnt recess the valves, then it falls .003 out of spec. As I stated above, I literally get anxiety over parts that fall outside of spec. Even by .001. I just can't use them unless they fit the right specification. I have mild OCD and it sucks. I won't know until I get all the parts here and measure everything though.

It really sounds like not much investigation was done on this machine shop before bringing the parts there. This is something we in the duramax world stress 24/7, it takes a machine shop with experience on this platform to do it right. If you're concerned with the quality of their work I would suggest scrapping the heads or double checking recession.


You seem to have enough knowledge to get into trouble on these topics but not enough to get yourself out of it. A perfect example is the thread awhile ago where you tried to apply class 8 tactics onto these light duty engines.


Unfortunately, this falls under something my grandfather taught me early. He would always say "Well Brad, lessons cost money and good ones cost lots. Hopefully this is a lesson for you."