Even if you have never seen the inside of an LS engine, you probably have heard the saying “Never look at the cam bearings!” That’s mainly because pretty much every junkyard LS engine has what looks to be wiped-out cam bearings. Steeped in much mystery and internet rumor, LS cam bearings have long been a sore spot for DIY builders, but why? The issues go much further than the looks of a stock bearing.

From the factory, LS and LT engines use tri-metal bearings made with a steel outer ring, a thin, hard copper-lead alloy second layer, and a soft lead babbitt material that supports the cam. The bearings have three separate cam bearing diameters, listed by position in the block front to rear. Number 1 is the front-most, then 2, 3, 4, and 5. Positions 1 and 5 are the same, positions 2 and 4 are the same, leaving the center position number 3 being the third size. These bores are different sizes based on the year of the engine.

This LM7 front cam bearing shows the typical LS cam bearing honing marks. With 150,000-plus miles on it, why risk it?

Are These Bearings Bad?

The primary issue when rebuilding an LS or LT engine is that when you pull the cam, the bearings look like toast. Every bearing looks worn, often showing copper. In any other engine, this would be a guaranteed sign of failed bearings, likely due to oiling issues. However, this is not the case with LS and LTs, as GM used a different procedure for these engines, and this is considered normal.

When an engine block is cast by the millions, you get a lot of variances. On the cam journals, just a slight amount of core shift can cause misalignment for the camshaft. You don’t want the cam bearing journals to be offset even a thousandth of an inch, which causes hot spots and premature failure. However, because the LS uses 3 different bearing sizes, align-boring the block is much more difficult. GM decided that instead of trying to line bore every block, they would instead use clinch-style bearings and align-hone them after they were installed, yielding a perfect align bore.

On the other hand, this is a damaged bearing in a Gen V L83. A lifter twisted, sending shrapnel through the engine.

The results are what you see here: brand new tri-metal bearings that look used up when they are just fine. For the average DIY rebuild, leaving those bearings in place is generally acceptable, but you do need to look for signs of actual wear, like hot spotting, blueing, grooves, and spun bearings. When in doubt, it is always recommended that you change the cam bearings, and if there has been any internal damage from a failure, especially a lifter, you need to remove the bearings to thoroughly clean the block anyway. So instead of “sending it,” set yourself up for success and not failure.

What Bearings Do I Need For My LS?

Once you have made the right decision to replace those ugly bearings that may or may not be good, you need to figure out what bearings you need. GM used three different cam bearing designs for the LS-series engines. The early design has a cam bearing journal measurement of 2.328 inches for the first and fifth positions (each end of the block). This design was used from 1997 through 2003. This design is ONLY usable on early Gen III blocks; you cannot use these bearings on later LS or LTs, and the newer design bearing requires expensive machining to convert an older block.

The first bearing design is well known for spinning in the block, and that’s just no fun. Beginning in 2003, and continuing through 2007, the cam bearing journals (outer diameter) were enlarged by .020 inch. Positions 1 and 5 were opened up to 2.3470 inches, with a bearing width of .630 inch. The width is the same as the first design. Unfortunately, these bearings also have a bad habit of spinning in the bore, so further changes were made.

In 2007, GM switched things up with a third design. Keeping the same outer diameters, the bearings were widened to .775 inch. The primary reason for the added width was to accommodate the VVT component of 2007-up LS engines, as the VVT system puts a little more load on the bearings during operation. The only difference between designs two and three is the added width.

When rebuilding a 2003-up LS engine, the third design is recommended. The wider bearing has more meat to grip the journal bore to resist spinning. The stock bearings are a bit weak in this regard, especially when running stiffer valve springs. The heavier springs put more pressure on the cam, increasing the risk of failure.

Are Aftermarket Cam Bearings Suitable For LS/LT Engines?

GM used clinch-style bearings and align-honed them after installation, but aftermarket bearings are full-round. If the line bore is not spot on, you can have tight spots in the cam rotation. This is where most shadetree LS “experts” shut you down with “You ain’t gunna line bore it, so just run ‘em stock deals,” which is not quite accurate. When selecting cam bearings, you need a set that uses a softer babbit on the inner face, such as Dura-Bond bearings. The softer babbit is more forgiving, allowing the cam to run true, without negative wear issues.

Spring pressures above 400 pounds at open generally require high-performance cam bearings, like those offered by King Engine Bearings. While this isn’t often considered in a typical DIY build, it should be. The cam bearings are critical for an engine to survive. You spend money to buy the good pistons, rings, lifters, and so on, and then run a stock cam bearing? That is just silly, especially when a set of new bearings isn’t expensive at all. Considering that when you get into the .625 inch-lift range, the valve springs need around 395 pounds of open pressure, you are on the ragged edge of whether or not those stock cam bearings can handle the pressure.

What About LT-series Cam Bearings?

GM’s engineers must have realized they had it figured out on the LS, because they used the third cam bearing design in all of the Gen V engines. The only difference is the fifth position, which is where the lifter for the mechanical fuel pump is located. This bearing is about twice as wide as the LS version, but that extra width is notched around the fuel pump lifter. The OEM bearings can be hard to come by; however, Dura-bond makes a full set.

Can I Install LS Cam Bearings Myself?

Of course you can! This is another one of these “internet myths” that LS engines require special tools to install the cam bearings, and if you are not an expert, you will destroy them. While there are some challenges, installing cam bearings in an LS block is pretty much just like any other engine; you just have to be careful.

You can purchase an LS cam bearing tool, which is specifically designed to fit the bearings. These are made with a machined aluminum driver head that mounts to a shaft. These work well, but you can also use the standard adjustable-sleeve style installer tool. The main issue with LS and LT cam bearing installation is that you are technically supposed to flip the block around and install the last two bearings from the opposite side of the block. This is to keep the tool lined up. Unfortunately, in our experience, this is nearly impossible, as there is not enough room to install the bearing and then remove the tool from the block because the three center bearings are smaller than the head of the tool. For this reason, we install the last bearing freehand, which some may question, but it works for us.

We recommend using a dead-blow hammer or rubber mallet so that you can find fitment or alignment issues before you damage the bearings. The bearings should be installed dry, no assembly lube or even engine oil. The bearings are supposed to be driven into place without any lubrication. Oil between the block and bearing will lead to a spun bearing and a ruined engine. However, do not forget to lube the camshaft before installing the cam.

Finally, it is imperative that the oiling holes in the bearings line up with the holes in the block. The best method is to locate the holes in the block, mark the end of the block with a marker, noting the position, and line up the bearings to match. LS cam bearings have two oiling holes in them, but only one in the block. You want the hole in the bearing to be centered in the bore and centered with the oiling port in the cam journal. Don’t under- or over-install the bearing, as this may cut off the edge of the oiling port, reducing flow.

LS and LT engines are possibly the most common in the country. Make sure your cam bearings are up to snuff before closing it up. A good set of micro-babbit bearings, installed with love and care, will help you send all those Ford and Chrysler boys to the woodshed.