Bryan Irons
Words and Photos by Bryan Irons @bryanirons
We were recently in a situation that many DIY wrenchers dream of and fear. We had a clean, spacious engine bay and used LS series engine on a stand with grandiose plans to make it great again for off-roading. So what were we afraid of? Well, with any major motor rebuild, it was the chance of discovering any mechanical issues that would halt the project even before we started it.
Since our internal combustion gasoline LS engine was borderline junkyard fodder to start with, the first important task was an ‘engine rundown.’ This should always be done to find tell-tale signs of how well the engine was maintained, if any parts need to be tossed, and its overall mechanical history and condition.
Everything we did was universal for any type of engine rebuild that can be done in any type of shop (be it a home garage, etc). All it takes is some due diligence, patience, sweat and some serious DIY knowledge. As we walk through our engine rundown, we’ll cover all of the details about the steps we took including the parts that were stripped, what we ‘discovered,’ and some interesting troubleshooting tricks.
We started by stripping all of the wiring and fuel systems from the engine, followed by cleaning and painting it. This may seem like the last thing that would need to be done, but we felt working from a clean slate was the best course of action. This also eliminated any worry about unwanted debris or even dropping ‘something’ in the internals that will only need to be fixed later on.
Once clean and the paint dry, we took a close look at the spark plugs. This helped determine how the engine was running and if it was burning any oil. Black, oily plugs indicate worn piston rings, a clogged PCV valve, leaking valve guides or several other problems. Plugs can also have soot buildup, miss-matched gaps, and worn electrodes. Fortunately, the plugs were in good shape and showed no signs of soot, oil or raw fuel. So far, so good.
Inspecting the valve covers was next. While spark plugs can reveal how well (or bad) the engine had been running, the colour of the components under the valve covers reveal how well the previous owner(s) maintained the vehicle. The darker the oil stains, the longer the engine ran between oil changes. It also indicates if the engine had ever overheated as well as more details about its condition. Crystalized oil and carbon can be easily scraped off and the oil stains we encountered showed there were plenty of kilometres on the engine, but otherwise, it was taken care of.
We then removed the rocker arms and pushrods. Once they are removed, keep them in order if they are going to be used again. To see if they need to be replaced, roll them across a flat surface. If they wobble, toss them. We took out the lifters as well. These, too, should be kept in the order they were removed if they are going to be used again.
Roller lifters should roll smoothly with very little play and make sure the flat tappet camshafts have a very slight crown. Flatness is a sign of wear and if they are concave in shape they are done with and should be replaced (along with the camshaft).
1 of 13
Bryan Irons
Before we even bolted the engine to the stand, we inspected the plugs. The ones on the LS were in good shape without signs of soot, oil or raw fuel. We were off to a good start.
2 of 13
Bryan Irons
With the valve covers off, we took a first look at the condition of the engine’s internals. While the oil stains seen here indicated the engine had a lot of miles, it was well maintained.
3 of 13
Bryan Irons
Thankfully, there weren’t any signs of debris in the crevasses of the rockers and they didn’t rattle. We also spun the crankshaft to make sure everything moved as it should.
4 of 13
Bryan Irons
The “valley” area on many other ‘V-shaped’ overhead valve engines makes it easy to inspect the lifters and pushrods but not on the LS. The pushrods should spin when the particular valve is closed. If they don’t, now is a good time to inspect your lifters, rockers and pushrods very closely.
5 of 13
Bryan Irons
Moving to the front of the engine, watch for torque-to-yield bolts like this dampener bolt. They can be used only once. When they are taken off, they’ll need to be replaced.
6 of 13
Bryan Irons
After getting the timing cover off, we saw the crank-driven oil pump and timing chain. We could get a little deflection out of the timing chain. It’s not horrible, but for the cost of a new one, it's best to change it.
7 of 13
Bryan Irons
To get the oil pump off, we had to remove the oil pan and take out the pickup tube. We’re old, so turning the motor upside down just made sense. Here, we see the windage tray and pickup assembly.
8 of 13
Bryan Irons
After taking off the oil pump, we inspected it for wear. The one on the LS was in excellent condition and we plan on reusing it.
9 of 13
Bryan Irons
We had to unscrew three bolts to remove the cam gear and use a generic bearing puller to remove the crank gear.
10 of 13
Bryan Irons
Before we removed the timing chain and sprockets, we aligned the timing marks to make the assembly easier to put back together. See the two dots lined up? We’re at the top dead centre here.
11 of 13
Bryan Irons
If the camshaft needs to be taken out, remove the valvetrain. Some engines at this stage may or may not have rocker arms, lifters, pushrods, or distributors. Pictured here is the camshaft retaining plate that also needed to be taken off before the cam was removed.
12 of 13
Bryan Irons
Here, the oil galleys extend to the end of the block that oils the lifters and valvetrain. Take a peek and make sure they are clear of any debris. There are long bolts threaded into the camshaft; this is for easier removal.
13 of 13
Bryan Irons
After getting the camshaft out, we checked for pitting, gouges, scores and other visible wear. Remember to look at the bearing from where they were taken out.
This brings us to the end of our in-depth inspection. Reports of our engine rebuild will continue in an upcoming issue and divulge the specifications of our new COMP roller cam and other parts we scored from Summit Racing!
www.summitracing.com
Next, we pulled the front timing cover off. This is where the oil pump is housed on the LS. We’re not a huge believer in swapping it out for a high-volume/high-pressure unit unless the engine will be heavily modified with plans on hitting five-digit RPM.
We also disassembled the gear-rotor-style stock pump and inspected it for scoring and wear. This style of pump typically only fails from incorrect installation or debris on its surface. But a worn surface on twin gear pumps is very hard to repair and it’s much easier to swap them out with new ones. Thankfully, these parts on our LS were in decent shape.
The timing chain on the LS is concealed behind the oil pump. Our block doesn’t have tensioners, adjusters, or guides for the chain. It’s important to remember that slack in the chain plays havoc on ignition timing, whether it’s controlled electronically or mechanically. Swapping out the tensioners, guides, chains and/or gears is just a smart move if they are worn. For engines with a timing belt, it’s best to get a new one (no matter how it looks) and learn how to mechanically time the engine.
We then flipped the LS over to remove the oil pan, which is an easier way to inspect the main rotating assembly. We turned the crank and looked carefully at the cylinder walls of the piston bores - all was good. Factory cross-hatching is always a positive sign but scoring, worn spots and loose metal parts just spell trouble. The oil pickup tubes typically have a screen on the bottom and can hold a treasure trove of headaches. We found silicone chunks, oil container lids and washers.
It’s always best to see and hear the engine running before a run down, if possible. Low oil or pulsating pressure indicates a bad or a spun bearing. Only if the engine shows a lot of wear do we recommend taking off the rod caps and/or the main caps. If the bearing surface looks copper in colour, it may be time for a complete rebuild. That copper colour is the base layer of the bearing and means the surface layer has worn. So, swap the bearings for new ones and ensure proper oil clearances. Torque the rod and main caps back to factory specification.
One of the reasons why we also flipped the LS upside down was to get the lifters away from the camshaft to properly inspect it. With the engine’s architecture, the lifters can’t be removed and inspected without removing the cylinder heads first. This was a bit of a hassle, but the lifters will move away from the camshaft after flipping the engine over. Yes, there are ways of keeping the lifters from contacting the camshaft without flipping it, but we prefer this method.
With the camshaft pulled, we looked at some of the cam bearings to see any abnormal wear and again, that copper colour. Roller camshafts - like the ones on the LS - always show very little wear even after hundreds of thousands of kilometres.
Taking an engine apart down to the camshaft (despite not finding any issues along the way) is not entirely necessary. With modern fuel-injected engines and tight factory tolerances introduced to vehicles in the last 20 years, it’s not all that uncommon to find a good engine in a vehicle that’s falling apart at a junkyard. We took further steps in this rundown to explain what to look for and since we’re not very good at leaving things ‘factory spec.’
Although we were happy with the results of the rundown, this is a ‘work in progress.’ Stay tuned for part II in an upcoming issue after we bolt our LS back together with some new goodies to make it more powerful, rev higher and last longer!