My First Stroker Part 3 - LS1 Engine Build

Our garage-built 383 gets its final parts installations, making this stroked LS1 ready to run!

Chris Werner Nov 1, 2006 0 Comment(s)

Step By Step

To make sure the 7.900 number is right, we're going to experiment a bit. We'll now set the checker out of the engine; then, in lieu of playing with the length of the checker while installed, we'll alter the position of the rocker adjuster instead. Here you can see this rocker system's cup-seat adjuster in action; turning it clockwise reduces clearance (lowers the adjuster out of its bore; right) and counterclockwise increases clearance (pulls it into its bore; left). Be sure during the following process of turning the lash adjuster that you're actually bottoming the lifter plunger and not simply hitting the adjuster's lock nut against the rocker; have a 12-point 3/8 wrench ready to back this nut off as far as needed.

First, we adjust the checker to 7.950 (the next possible length pushrod we could buy) and see if it'll work. It doesn't: the adjuster causes the lifter plunger to bottom out at only a turn and a half. After adjusting the checker to 7.850, we try again and find that after two full turns on the adjuster, there's still a ton of plunger travel left before bottoming it out. In fact, the plunger doesn't bottom until almost 3 1/2 turns of the lash adjuster-way past Jesel's proper spec. (Here you see us backing the lock nut off even further to get to this extreme 3 1/2 turn position).

Bringing the checker back to 7.900 inches and putting it in place, we find that at a quarter turn on the rocker adjuster, there's too much play in the lifter plunger; but at exactly two full turns, the plunger bottoms out. This means that where we'll need to be on the lash adjuster is somewhere between .25 and 2 turns (2 1/2 when tested on the exhaust)-just about what Jesel specifies. We double-checked on cylinder number eight (passenger side rear) and got near-identical results: so 7.900 is as good as we are going to get!

Our pushrods of choice are Manley PN 25712-16 Swedged End Pushrods. Retailing for $140, these suckers are made from heat-treated 4130 chrome moly and feature a 0.080-inch wall thickness and a black oxide finish. While these particular pushrods are 5/16 in diameter, larger diameters are available for truly sick valvespring pressures. They're manufactured in Manley's Lakewood, N.J. facility for top-notch quality and are readily available in length increments of 0.050 inches (and in some cases 0.025).

After a thorough cleaning, slide all 16 pushrods into their holes. It's critical that you look through them to make sure no crud occupies their center oil passages; otherwise, the upper valvetrain could be starved of oil and accelerated wear will result.

We need to install and adjust each rocker arm set one at a time since at any given point in the crank rotation, different valves are open on various cylinders. Remember, each rocker assembly can only be bolted on when both valves on that cylinder are closed. We begin with cylinder number one. Before popping the rockers atop the stand, we lube the tips of both pushrods with Jesel's provided extreme pressure lube; this will ensure proper break-in of the pushrod tip/rocker adjuster surface meeting (an area that experiences a large amount of force). This is the only area of the Gen III engine where any sort of "break-in" lube is required.

To ensure we are at the number-one firing position (where both valves are sure to be closed), we can again look through this convenient hole in the lifter valley and see whether both cylinder one's lifters are on their cam lobe base circles. Recall that you might have to press down on the pushrods to get the lifters to come down out of their trays.

Engine Mounts

One of the last remaining items that must be installed before we can drop our stroked LS1 into the engine cradle is a rather basic one: the engine (or "motor") mounts! The stock mounts will be reused, but we treated ourselves to an ARP bolt kit (PN 434-3102, $22.50) consisting of stainless steel, hex-head bolts.

Crank Pulley

While engines of years past utilized a crank pulley bolted to the front of the engine's harmonic damper (often referred to by the misnomer "harmonic balancer"), the Gen III has a one-piece harmonic damper with machined surfaces for the accessory belts to ride on. While it's possible to reuse a GM unit on a stroked LS1, we're going to take a page out of the classic hot rodding manual and replace it with a smaller-diameter "underdrive" unit from SLP. By allowing the power steering pump, water pump, and alternator to turn more slowly for a given engine speed, fewer horsepower are lost and accessory life is increased.

It seems like a no-brainer, but thanks to its press-fit design, installing the crank balancer can be one of the most strength-demanding portions of an engine build. Tools are available-or can be improvised-that help you gain the mechanical advantage you need to slowly press the unit into place. But unfortunately, they all involve turning in the direction of crank travel-meaning the crank will want to rotate and work against you. A GM J 42386-A Flywheel Holding Tool (or similar unit that bolts in place of the starter motor) is a good idea as it will keep the crankshaft from spinning and make your life a lot easier.

Absent your access to such a tool, there are some other options to help make sure you'll be able to get the balancer on without simply turning the engine over. For example, you might choose to install the balancer before the rocker arms go on: put in the spark plugs, and all eight cylinders will have sealed pockets of air in them to resist piston movement. But since we have already installed and adjusted our rockers, we'll get the balancer on as far as we can; then, if need be, we'll wait until the transmission and driveshaft are hooked up to tighten the crank bolt the rest of the way (they'll help resist crank turning significantly).

The Lunati crankshaft-though it has a keyway slot for the oil pump drive-is not machined for the use of a keyway to help locate the harmonic damper. While such an additional keyway is only really necessary for supercharged applications, it would have been nice if Lunati had pre-machined its crank for one, especially since most aftermarket harmonic dampers have a corresponding slot ready. Though the damper is neutrally balanced, we'll still do our best to line up SLP's would-be keyway slot as close as possible to the Lunati keyway further back on the crank snout. In this way, the SLP-engraved timing markings on the outside rim of the balancer will be at least roughly close to where they ought to be (although a need for a timing light is an unlikely scenario on the electronically controlled LS1).

Cooling System

There are a few cooling system items to install onto our LS1 before the engine will go into its home under the hood of our project 2001 Firebird. These primarily include the water pump and thermostat.

As to the water pump, we're reusing the stocker, but an upgrade to a new GM water pump is not a bad idea if your vehicle has a lot of miles on it. This isn't your only option though: you may want to upgrade to an aftermarket mechanical water pump or even swap to an electric pump for reduced parasitic drive losses (it purportedly takes less energy to turn such a pump electrically than it does to spin a pump mechanically). But this author simply can't be convinced that an electric pump can ever be as reliable as a mechanical pump. Combine this street-minded attitude with the interest of cost savings, and we're going with the GM pump.

The thermostat is a cooling-system item that hot rodders have swapped out for decades. With any high-output engine, a cooler thermostat should be used to help ward off detonation. While the stock 195-degree unit is good for emissions and winter warm-ups, it's not so good for horsepower.

Intake Manifold and Throttle Body

The increased cubes of a stroker are worthless unless the intake system is able to provide enough flow to fill them up. Early-model LS1 engines with the original LS1 intake manifold are in serious need of a higher-flowing intake; later LS1s had the LS6 unit, which flowed much better. But even this intake can't match the flow capabilities that aftermarket manifolds afford with their larger runners and increased throttle body openings.

There are quite a few intakes on the market that will work on an LS1, but very few that are composite (and hence virtually impervious to the heat soak issues that plague aluminum and steel manifolds). While our stock LS1 had previously been upgraded to a composite 78mm F.A.S.T. LSX intake manifold (see "F.A.S.T. On The Gas," Jan. 2006), even its larger-than-stock throttle body opening could prove restrictive now that we're running 6.3L of displacement. Fortunately, F.A.S.T. makes it easy to upgrade its LSX intake and sells its 90mm top shell separately, avoiding the need to purchase an entirely new manifold. We also need a bigger throttle body to match, and so looked to Holley for a new LS Series unit (since the Holley throttle body does not include a new seal, we ordered a 90mm one from F.A.S.T.: PN 30-54011, $9.27). Conveniently, all of these items can be installed while the engine is still on its stand.

Intermission! Dropping the Engine into the Subframe

We've reached the physical limit of bolting parts onto our LS1 while it's still on the engine stand: the reality of having to attach a chain to the engine in order to lower it into an F-body's subframe means that items like the fuel rails will have to wait, lest they be accidentally broken or damaged. Once the engine is secured in the subframe, though, more can be done to get it ready to be inserted into the car with relatively little difficulty.

Now is also a good time to install little items you might not have transferred to the new engine yet. For example, the ECT sensor screws into the front of the driver side cylinder head and a plug goes into the same hole at the rear of the passenger side head. Put the oil filter on if you haven't done so already. You should also put in place-even if loosely-all fasteners you removed when taking the engine out of the car and stripping it to the block. For example, there are several attachment bolts for ground straps on the heads and engine block. Hopefully you've labeled all of this stuff when you took everything apart so you know what goes where! It's easier to do all of this now as access to some areas of the block will be restricted once the engine is sitting in the subframe (also known as a cradle).

Fuel Rails

With the engine in the subframe, we can continue installing components onto the engine, and we begin with the fuel rails. Avid readers will recall that this vehicle has already been upgraded with a Racetronix fuel system, including pump, wiring harness, and 60 lb/hr Siemens/Mototron fuel injectors (see "Fuel: Up!," April 2006). This system will be able to provide all of our necessary fueling, even if we have to wire in a pump voltage booster to be able to safely handle large amounts of nitrous injection.

But we're looking at 450-500 rwhp naturally aspirated, and likely an eventual 200hp shot of nitrous on top of that. Also taking into consideration that our ZEX nitrous system is designed to receive fuel from a fitting on the fuel rails, we wanted to make sure the rails were large enough to accommodate all of this flow. We called Speed Inc. and ordered an LS1 fuel rail kit; follow along as we bolt it on.

Modifying the PCV System.

Since we had to cut the PCV baffles out of the valve covers in order to provide adequate clearance for our valvetrain, the system can no longer be used without gobs and gobs of oil entering the intake manifold. Though technically the PCV system is an emissions piece that should not be altered without incurring the wrath of the EPA, in this case we had no choice. Here's how to go about it.


We're about done with this segment of the story, but wanted to leave you with a few final tips and tricks on installing the LS1 into the engine bay of the ever-popular Fourth Gen F-body. It's not as hard as you might think, and the engine-in-cradle system means a good chunk of your drivetrain, wiring harness, and exhaust system can attach to the motor before it's installed, saving much of the shaved knuckles and cursing that invariably come from working in cramped underhood quarters!




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