In case you're deep into a diesel motor rebuild and spot the cylinder liner height isn't quite striking the mark, reaching for any liner shim is usually the quickest way to get things back again on track. It's one of individuals small parts that will doesn't appear to be much—basically just a thin ring of metal—but if you disregard the requirement for one, you're basically appealing a head gasket failure to take place faster rather than later on.
Whenever you're working on a block, especially a single that's seen a lot of mls or has been machined before, the particular "counterbore" (the corner where the liner sits) can get worn out. This causes the liner to sit too low in the block. If that liner isn't sticking upward just the correct amount, the top gasket won't have the "squish" it needs to seal properly. That's where our small friend the shim comes in to save the morning.
That annoying gap and why it matters
So, let's discuss why we even care about liner protrusion. You've got your engine block, and you've got your liners. When you drop a liner into the hole, it's supposed to stick up above the deck of the block by a tiny, particular amount—usually just the few thousandths of an inch. We call this "protrusion. "
If the protrusion is actually low, or even heaven forbid, the particular liner is even or recessed, the particular cyl-head won't put enough pressure upon the fire band of the mind gasket. When that occurs, combustion gases start leaking out, coolant starts leaking within, and suddenly you're pulling the head back away two several weeks after you completed the job. Making use of a liner shim could be the standard way to provide that height back into spec without having to replace the entire engine block or do some incredibly expensive custom machining.
Obtaining the measurements directly
You can't really guess with regards to shims. You may think you can eye itself it, but we're talking about ranges thinner than a human hair. In order to figure out if you need a liner shim , you're going in order to need a switch indicator and also a keeping bridge.
First, make sure the counterbore is clean. I mean actually clean. Any bit associated with old carbon or rust is going to throw your own reading off. Once it's spotless, drop the liner within (without the O-rings for now) and clamp it right down to simulate the cylinder head being torqued. Today, take your call indicator and calculate the height difference between the top of the liner flange and the engine block terrace.
When the manufacturer states you need. 004" to. 006" associated with protrusion and you're sitting at. 001", you know you're in trouble. This is exactly when you start looking through your kit for a liner shim that can create up that. 004" or. 005" distinction. It's a casino game associated with precision, but it's honestly pretty gratifying when you get it dialed in properly.
Why do counterbores wear out there anyway?
It seems weird that a heavy piece of iron would certainly just "wear away" under a static liner, but this happens. Over thousands of cycles, the liner actually moves just a small bit. It vibrates and "frets" against the block. Over time, this wears throughout the ledge. Also, when the engine has actually overheated or had a loose head bolt, that movement will be exaggerated.
Sometimes, an earlier mechanic might have even machined the block deck to straighten it away but forgot in order to cut the counterbores deeper, or these people might have cut the counterbores to wash up some pitting. Either way, once that metal will be gone, the liner shim will be your only genuine way to build that height back up.
Selecting the most appropriate shim for the work
Not just about all shims are developed equal. Most of the time, you'll find a liner shim made of stainless steel since it needs to be difficult and resist corrosion. You can generally find them in different thicknesses—common ones are. 002",. 004",. 010", and so forth.
Some guys like to stack all of them, but honestly, if you possibly can use one one thicker shim instead of three thin ones, go that route. It's simply fewer surfaces that could potentially shift or compress. Should you choose have to stack them, just create sure everything is usually hospital-clean. Even a tiny speck associated with dust between two shims can mess up your last protrusion measurement.
Stainless vs. Real estate agent?
You might from time to time see copper shims in older apps or specific top-end setups, but for most modern heavy-duty diesel powered engines, stainless is the gold standard. It doesn't compress as much as copper, which is what you want whenever you're trying to maintain a very specific clearance underneath the heavy clamping force of a cylinder head.
Getting it installed with no headaches
Once you've done the math and chosen your own liner shim , the particular installation can be quite straightforward, but you've obtained to be cautious. You'll want in order to place the shim directly onto the counterbore ledge before you decide to drop the liner in.
A professional tip here: don't make use of any heavy grease to "stick" the shim in location. If you make use of something too heavy, it may actually hold the shim up and give you a false reading, or even worse, it could prevent the liner through seating fully once the engine will get hot. A very lighting film of clean engine oil is usually all you need to continue to keep it through sliding around while you lower the particular liner.
Following the shim and liner are in, do your measurements 1 more time. I realize, it's a discomfort to it back again out if it's wrong, but it's a lot much less of the pain compared to rebuilding the whole top end afterwards. If your protrusion is currently within the factory specs, you're good to go.
Common errors to prevent
A single big mistake I actually see people create is only checking out one side from the liner. You need to always gauge the protrusion at least 4 points around the particular circumference of the particular liner. Sometimes the particular counterbore is used unevenly—maybe it's deeper on the exhaust system side than the particular intake side. In the event that you only calculate one spot, a person might think you're fine, but the liner could really be "cocked" within the hole.
One more thing is forgetting to accounts for "crush. " Some head mechanical seals are designed to compress a certain amount, and the manufacturer's protrusion spec accounts with regard to that. Always adhere to the shop manual for your specific engine model, just because a Cummins might need a completely different set up than a Cat or even a Detroit Diesel powered.
Lastly, don't try to work with a liner shim to fix the cracked block. In the event that the counterbore corner is actually damaged or crumbling, a shim is simply a band-aid on a gunshot wound. At that point, you need to look into getting the particular block sleeved or even replaced.
Why skipping this task is the bad idea
It's tempting to just "send it" when you're tired and the components are taking forever to arrive. But skipping the liner shim if you understand the protrusion is low is the recipe for disaster.
Think about what's occurring inside that cylinder. You've got thousands of pounds associated with pressure every period that piston hits top dead middle. If the liner can move even a fraction of the millimeter because the head isn't keeping it down tight, it's going to vibrate. That vibration will certainly eventually eat via the head seal. Then you've obtained white smoke being released the tailpipe, or worse, you'll discover "forbidden milkshake" (coolant and oil combined together) under your oil cap.
Taking the particular extra hour to measure and set up a five-dollar liner shim is the greatest insurance policy you can buy for your engine. It ensures that the pressure stays where it belongs—inside the combustion chamber—and keeps your motor running for one more few hundred 1000 miles.
Covering it up
From the end associated with the day, the liner shim is a simple tool for a precise problem. It's not flashy, and nobody's likely to notice it once the particular engine is back together, but it's the difference between a professional repair along with a "backyard special" that fails within a month.
If you're in the middle of a project plus things aren't lining up, don't perspire it. Just get a micrometer, verify your heights, and obtain the right shims ordered. Your motor (and your wallet) will definitely thank a person down the street when you aren't performing the whole job over again. Shop work is all about the tiny details, and in the field of engine blocks, it doesn't get very much more "detail-oriented" than the humble liner shim.