cts1950 wrote:
Now I am as nervous as a long tailed cat in a room full of rocking chairs. It is too late for me to change what I have already put together this weekend. All I can do is hope by using copper coat on the gasket surfaces the head gasket will hold. I really appreciate the professionalism and the sharing of info on this forum, much to be learned. I debated with myself about going with the thick head gasket but thinking it was important to match what had been installed before hand. I was uncomfortable about bottoming the studs out based on a report from another stud manufacture that it was best practice to have the stud floating so that the twisting of the stud would not affect a accurate torquing. I mistakenly took ID's add to have been the approved method from ARP. I will have to keep my fingers crossed. I have had some experience working on 2 stroke gm diesels ,rebuilding in-frame on a marine 8v 92 and a 4 71 much simpler engines. I currently drive a restored 67 Jeepster with a Isuzu 4jb1-t which got me looking at the Liberty crd as 2nd jeep.
As long as you haven't milled the block, which increases piston 'stick out' (COMPARED TO THE BLOCK, NOT LINER, liner 'height' is set separately) You'll be absolutely fine with running the Head gasket Thickness it originally came with.
Honestly, I completely fail to see the reasoning behind 'going with a thicker gasket'. For solving head sealing issues.
Our head gaskets are FLAT. They are Parallel. It won't make a skiff of difference if the gasket was 1 inch thick. or a mere no hole thick. How much the liner sticks UP and bites into the HG is the ONLY issue here!!
Do not think that a steel shim gasket will 'conform' as a fibrous gasket will Sure, that thin layer of sealant (either the original layer, or the added copper kote) will help with extreme tiny imperfections.. But a steel gasket will not 'make up' for any larger imperfections. regardless of how thick it is.
The raised part of the liner, NOT 'area a', (see attached pic) but inboard, does come close, but even the thinnest no hole gasket still gives ample clearance to the head. No reason to suspect contact, unless somebody forgot to clean off the carbon from that ring!!
This pic shows the 'imprint' of the liner's 'bite' transferred through the head gasket, onto the head.
It's basically 2 lines. the inner line is the actual edge of the gasket. the Outer line represents the outside diameter of the liner.
Those 2 lines define the area 'a' as shown in the pic below. Yes, that 'imprint' can be felt. That area on the hg was also devoid of any of the original 'rubbery' type sealant. The head gasket was 'shiny' on both side, within those 2 lines.
It isn't hard to see how the original 'bite' has lost preload... between all the imprinting, and the loss of thickness in the most crucial area of the head gasket..
Various thickness of HG's are for ONE thing. To maintain a certain distance of the tops of pistons, and the valves, and yet maintain a certain amount of chamber volume @tdc. All the tuning algorithms are based on 'X' cylinder temp, at X pressure, a X degrees of crank position. Changing up the combustion volume will sway how hot, how quickly, and how complete the injected fuel burns.
We don't have knock sensors, or exhaust sniffers to adjust our tune. It's all wired based on coolant temp, ambient air, and intake pressure.. The computer has no way of knowing if the combustion chamber has been altered. All it knows is there 'should' be x amount of heat from compressed air, and the amount of fuel should respond accordingly when the crank is at 'x' degrees of rotation. Granted, the thicker HG will probably not alter how all this works, on a percentage basis.. I can't see how it wouldn't affect it 'some'. .004 inch difference isn't much!!! each gasket 'jump' in thickness increases chamber volume by .044 cubic inch.
A 'sealed' cylinder, with removable liners, is all based on how much BITE the liner has on the HG.
I modified this FSM pic to fully show what I'm talking about.
The head gasket actually goes over the top of the liner. Area 'a'. This pic shows the liner's shims are missing, so that is the reason for the negative height. This is only for measuring purposes. The liner is actually supposed to sit between 'level' (0.000) to a +0.002 Positive height.
So, when the liner is either 'level-to-positive height' that 'bite' at 'area a' is the actual seal keeping combustion gasses in the cylinder. When that 'bite' is lost, the first place high compression goes is down along the liner bore... straight into the coolant. Those 'shims' are NOT seals, and are easily compromised.