LSx Engine Rebuild

LSx Engine Rebuild Overview

We may be a bit biased here at MRK-Motorsports, but it seems pretty clear that GM’s LS series are just about the hottest engines in the automotive performance world today. In the nearly 15 years since their introduction in the C5 Corvette, LS engines have become renowned for their ability to make big power numbers with relatively few modifications, and more recently, LS’s have become the engine choice for anyone looking to swap a V8 powerplant into almost any make or model (…including Fords and many imports…).

Rebuilding an engine is one of the core fundamentals of hot rodding, and as the LS series of engines becomes more and more popular, we felt that it’s important to revisit the basics. Today, hot rodders of all types – even small-block chevy veterans – are building their very first LS engines.  We decided to put together some real world tips for virgin LS builders, and enlisted the help from LSX Magazine sponsor Chad Golen, owner and operator of Golen Engine Service to give us some tips on building LS Engines for a performance car.

Rebuilding an LS engine is a great way to make more power thanks to more cubic inches and higher compression pistons, as well as other goodies like a new cam and cylinder heads that can be added during a rebuild. Here Chad Golen shows us how it’s done at Golen Engine Service shop in Hudson, New Hampshire.

1) Selecting your Core – Iron Blocks

As with any engine build, it is vital that you start with a good, rebuildable core for your engine block. If you’re rebuilding the engine that is already in your car, then at least you have some idea of its basic condition, and what to expect when you crack it open. If you are getting a used engine from somewhere else though, Golen has a few words of warning. Golen says that iron LS blocks are a pretty safe buy even when you don’t know the history of background. They can be over-bored safely and are more durable than their aluminum counterparts.

The most desirable castings are the 6.0L LQ9 or LQ4 truck blocks, which are production cast iron blocks, with 6-bolt iron main bearing caps, 9.240-inch deck height, and offer a 4.00-inch bore.

2) Selecting your Core – Aluminum Blocks

“When you are looking at buying an aluminum LS engine from a scrap yard, or off the internet, do your best to only buy an engine that you have some kind of confirmation that it was running before it was pulled from the car,” explained Golen. “You need to especially careful since the older OE aluminum blocks can only be honed about 7 thousandths, from 3.898 to 3.905. which can clean up any decent used LS1 engine.

Unfortunately… they can’t be bored out any further to clean up any damage that might have caused an engine to stop running. It’s been my experience that more often than not, when you find an LS1 engine in a junk yard, it’s there for a reason. If you can avoid it, don’t buy an unknown engine. Iron blocks are usually okay to buy used because they can be bored out quite a ways to clean up the cylinder walls. Just be very careful.”

3) Selecting your internals – What to Upgrade

All things considered, LS motors come from GM equipped with a pretty tough rotating assembly. But if you are looking to produce quite a bit more power with your LS, there are a few components you should address during a rebuild. The crankshafts are pretty strong if you’re going to be building up to and around 600 horsepower or so. The weakness is the rods and pistons.

The sky is truly the limit with LSX builds thanks to a huge aftermarket that offers rebuild kits that can fit your exact needs for your engine.

“When you’re building up an LS short block for a Camaro, Firebird, or C5 Corvette, the main parts you need to focus on are the connecting rods and pistons,” Chad told us. “The most common failure we see in stock LS engines is the weak spot near the wrist pins cracking, and the tops of the stock pistons chipping. Luckily the aftermarket for LS rods and pistons is huge, and there are a lot of great options out there. There are inexpensive forged LS pistons available for just about any type of build. The stock crank is good for about 600 horsepower, so it’s just fine to reuse unless you are looking for really, really big power.”

So, for most re-builds 600 HP and under, think stock block and stock crank; but new rods and pistons. Obviously bearings, rings, and machine work are required in any case.

If you are doing any kind of performance reubuild on your LS engine, it’s vital to upgrade to stronger pistons since the weak area around the stock piston’s wrist pins is a common area of failure.

4) Some Quick Tips on “LS” Machine Work

Once you’ve got the right core, and all your parts selected, it’s time to do the machine work. Machine work on an LS re-build can range from a quick hone to clean up the cylinder walls on a stock refresher build, to boring out the cylinders for maximum displacement (if you’ve got an iron-block). Regardless of how much machine work your engine needs, this much is for sure; the quality of the machining performed will make, or literally break your LS rebuild. Luckily, your machine shop is likely to be experienced with LS-engine rebuilds, and most performance machining tips apply in the LS world.

Properly performed machine work will make reassembly much easier on you. Poor machine work means that you’ll just be tearing your engine apart again right after you fire it for the firs time…

Golen explained some of his basic recommendations: “When you’re having an LS block machined, make sure the shop is using a torque plate – which is where an adapter plate is bolted to the block to simulate the cylinder head being torqued in place, while the machine is doing the hone. There should even be a gasket bolted in there too. This is especially important when working with any of the aluminum LS blocks. This will make sure that the bores are as straight as possible with no distortion. Along the same lines, you should also have the deck of the block checked to make sure the cylinder head mating surface is as flat as possible.”

These are only the two most basic machining procedures typically preformed on an LS rebuild, but your machine shop can let you know what other machine work (line honing the mains, polishing your crank journals, etc.) that your specific engine will need.

5) Cam Bearing Blues

If you are the adventurous type that want’s to assemble your very own LS engine, Golen has a few bits of advice for you.“On LS engines there are a few areas you need to pay attention to, starting with the cam bearings. When you are installing the cam bearings, you want to be extra careful and make sure that the bearings press in good and tight. Pay close attention here. If they slide in nice and easy and don’t have a press-fit, that is a recipe for disaster, and ultimately that will be a sign that the block is no good. You’ll spin a cam bearing, and could possibly destroy the entire engine.”

A good torque wrench will be your best friend if you decide to assemble your LS block yourself.

6) Advice on the little things

Sometimes an ounce of prevention is worth a pound of cure. That means, don’t scrimp on some cheap parts that could save you money.“Go ahead and get yourself a new block plug kit, and be sure to replace the plastic barbell oil restrictor in the block,” said Golen. “One nice thing about the LS engines is that typically, all of you engine covers are completely reusable – valve covers, valley cover, front and rear covers – but please just be sure to get some new high quality head and intake gaskets from GM or Fel-Pro. For the front and rear covers, there really isn’t any need to buy the whole new cover with the gasket already pressed in. The seals usually pop in if you carefully tap them in with just a rubber mallet.”

7) Head Bolts – The Biggest Mistake an LS Builder Makes

If there was one thing that has killed more LS rebuilds than any other – it’s re-using the stock head bolts. It is very important to note that the LS head bolts are not re-usable.

Golen recommends using high quality ARP head bolts and GM head gaskets. He tells us, “We like to use ARP headbolts, and GM multi-layer-steel head gaskets in builds up to about 550 horsepower. It’s also a good idea to look into ARP Main studs and bolts when you are ready to do your assembly. Good hardware is a relatively cheap insurance policy for your engine.”

Over 550 HP, ARP’s head studs, and better Fel-Pro gaskets should get the call.

As with other engines, it’s a very good idea to do a pre-assembly on your LS engine to make sure that all of the machine work was performed to spec, and to confirm that you have all the right parts. Get yourself some plasti-gauge, and go to town.

Items like the barbell oil restrictor in the back of the block need to be replaced while you are going through your engine.

8: Stroker Specifics

There’s no replacement for displacement, and if you’re looking to stroke your LS engine for more cubic inches, there are a few factors that you need to take into consideration during assembly.

Golen tells us, “The very bottom of the cylinder walls on LS engines need clearanced 60 to 80 thousandths when you are building a stroker, because the connecting rod bolts will hit them. Take black magic marker and mark where you need to grind, and be careful with the metal shavings.”

There are some areas of the block that will need a bit of “massaging” if plan to go the stroker route.

Even though you have to do some clearancing, stroking an LS is actually a little easier in many ways than stroking a traditional small block – you don’t even need to use a small base circle cam. The only other consideration with stroking an LS is that you will need to space out the windage tray a bit from the crank with some washers or spacers.

Depending on how radical you go with a stroker crank in an LS block, you could get away with just a few washers to space out your windage tray…or you might find yourself doing a bit more work to get the tray to clear the crank’s throw.

Golen offered us this additional advice on stroking an LS, “A four inch stroke is about as big as you can safely go on LS1 block, but with an LS3 block you can get away with a bigger 4.125 stroke, which will actually give you 427 cubic inches with the stock bore.”

9) Stock LS Cylinder Head Basics

The heads on LS series engines are the bread and butter of their power production capabilities. The design is light years ahead of anything that came on a Gen I small block, and even in stock form they are capable of producing power levels that were only possible in a Gen I with aftermarket heads.

For serious power potential, you can pick your pleasure from any one of the numerous aftermarket LS cylinder head companies. Or, if you are more budget minded, you can squeeze plenty of power out of several very capable stock type LS heads.

Adding bigger valves to your stock heads is a great budget minded solution to replacement heasds.

For a cheap build, you can get away with stock LS1, LS6 or LS2 heads.

“On LS1 cylinder heads, a quick polish and moving the intake valves up to 2.02 inch stainless valves can get you into the 500 to 600 horsepower range with a nice cam. They just need a little bit of work to reach their full potential. You can also use 5.3 truck heads for a nice compression bump on an LS1, and they even flow about the same as the regular LS1 heads. Also, the 243’s [commonly referred to as the “LS6” or “LS2” heads] are a great budget option, and can make a ton of power in the right combo.”

However, as we’ve covered elsewhere, the L92/LS3 heads are an inexpensive upgrade and worth a ton of power.

“Probably the best power potential to dollar value in LS cylinder heads would have to be the L92/LS3 rectangle port heads,” advised Golen. ” But don’t forget – they can only be used on engines with a bore of at least 4 inches – like a 6.0L iron truck engine, or an LS2.” In addition, you’ll need a new intake manifold, rockers, and gaskets.

Having the right tools can make all the difference in how smoothly your rebuild will go. Here we see how easily valves and valve springs can be installed with the right type of spring compressor.

Golen also offered this additional advice, “Don’t reuse your stock rocker arms when you are reassembling your heads. You can get GM stock replacements cheap enough. Also remember to use valve springs that match the lift of your cam. This isn’t an area where you want to try your luck.”

Just add your accessory drive, intake, and sensors, and you are ready to drop your fresh LS engine in your favorite street or strip ride.

10) Follow Other Builds – do your LS research

When it comes down to it, the LS series of engines are like most any other internal combustion engine. Granted, they are a whole lot more efficient and powerful than most others, but the basics are the same. While hope these LS specific tips from the engine experts at Golen will help you on your way to the path of LS engine building righteousness, nothing will replace doing some research on your own to become an LS expert. LSXMAG and many web forums are excellent sources of information on LS building. A few hours of reading can replace weeks of anguish if your build goes south.

And – while we are at, we should suggest – if you’re looking for a tough LS short-block replacement to add your own heads and cam combo to, then Golen Engine Service also has you covered.

A special thanks to Chad Golen for his help with this guide, and we have a ton of respect for this experienced builder. Check out some of his sample builds below, and rest assured, if you don’t want to build your own, or need some advice, clicking on any of the links below will get you some serious LS horsepower in a jiffy.



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