Tech / Tech Projects

Back in Black Nighthawk LS (Part 2): Heads, Valvetrain, Oiling System & More

 

Editor’s Note: Mike Mavrigian’s shop, Birchwood Automotive, specializes in street performance and racing engines as well as vehicle restoration. We covered his last build, a 499 cubic inch Mopar 400 big block. This time, he’s building a 408-cubic-inch LS engine based on a 6.0L cast iron block. We covered the short block in Part One of the build, and Part Two picks back up with the installation of the cylinder heads and valvetrain, timing chain, oiling system, cover plates, and balancer.

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Our timing set is Cloyes’ Hex-A-Just, which provides adjustment of both crank and cam gears. The kit includes cam gear, crank gear, oil pump drive gear, cam gear thrust bearing, heavy duty single roller chain, and an eccentric cam gear adjustment button.

The cam gear features the appropriate reluctor projections for use with an LS2-style, front-mounted camshaft position sensor.

The cam gear’s thrust bearing is installed onto the rear of the gear, with the black side facing the block. If the bearing is installed backwards you will damage it.

With the three cam gear bolts loosened, a hex wrench is used to rotate the advance/retard button. Here the button is adjusted to zero position.

A Cloyes chain damper reduces harmonic slop in the chain. LS block cam-to-crank centerlines are on the short side, resulting in a fairly loose chain. Using a damper is strongly recommended. Some LS blocks like ours do not feature threaded mounting holes for a timing chain damper, so we used a Trick Flow damper adapter bracket. The bracket shares three of the camshaft retaining plate bolts, with no block modifications needed.

We verified camshaft timing with a degree wheel.

The Melling direct-fit performance oil pump is a high volume unit. The pump was mounted to the block with ARP 8mm x 1.25 bolts, with a dot of threadlocker applied to the bolt threads.

The rear oil passage hole is plugged with a new OE plastic “barbell” plug. The end of the plug with the blue O-ring seals the plug at the rear of the block (the end without the O-ring is inserted first). Lightly oil the O-ring prior to installation. The rear oil plug is installed until flush with the block surface.

Our custom valley plate was machined from .250” thick 6061 billet stock. Unlike the OEM cover, the plate runs flush front and rear. The casting depressions at the front top of the block were filled with All-Metal body filler to create a flush-front block area.

COMP Cams’ LS front cover has provisions for mounting a timing pointer, and the front-mounted camshaft position sensor’s location is adjustable.

If your block is an OE-spec with a standard camshaft height location, the sensor adapter is installed with the sensor eccentric hole at 6 o’clock. It seals with a square-profile O-ring.

If you have a raised-cam block, position the sensor eccentric hole at 12 o’clock.

The installed front cover with the cam sensor installed. The COMP cover is designed to accept any timing pointer intended for a big block Chevy. I used a TCI adjustable timing pointer.

Before fitting the oil pump pickup tube to the oil pump, first verify which O-ring is required. Melling provides two different O-rings with its pump; a drawing included with the pump clearly indicates which O-ring is correct for a given tube style. Lightly oil the O-ring and insert the tube into the pump by hand, making sure that the tube’s flange is flush with the pump surface. Do not try to achieve a flush mount by simply tightening the 6mm bolt.

Test-fit the windage tray and rotate the crank to check for rod/rod bolt interference. Typically when crank stroke is increased, you will have a clearance issue. We spaced our windage tray by 0.190” using washers, gaining approximately 0.100” of clearance.

Our Holley cast aluminum oil pan clears a 4.000” stroke crank. I had planned to have the pan powdercoated in black, but Holley now offers this pan black ceramic coated. The pan is mounted using a Fel-Pro pan gasket and ARP 12-point 8mm and 6mm stainless bolts.

Our roller lifters are Comp’s OEM style roller lifters with upper flats that engage the OE plastic lifter guide trays.

Before installing the lifter/guide assembly, drill a 5/16” drain hole at the bottom of each lifter well. This allows better oil drainback, preventing oil from puddling up inside the wells. The drain holes are located on the outboard side of the guides (facing the cylinders). Be sure to deburr and clean the guides after drilling.

Each bank of four lifters is installed as a unit. The OE type 6mm shouldered lifter guide bolts must be used to properly center the trays.

With lifters snapped into the plastic guide, they are held away from the cam. Once the lifter trays are secured, use a pushrod to push each lifter downward to make contact with each cam lobe. Notice the very visible “FRONT” designation on the Fel-Pro MLS head gasket. The gaskets are directional (dedicated left and right) and must be positioned properly to avoid covering the water jackets.

The Trick Flow GenX® 225 aluminum cylinder heads feature 225cc intake/80cc exhaust runners with Trick Flow’s full CNC Competition porting. Features include 2.055 inch intake/1.575 inch exhaust valves, dual 1.300 inch valve springs, titanium retainers, and seven degree locks. Trick Flow changed the valve angle from 15 degrees to 13.5 degrees to decrease valve shrouding, increase mid-lift airflow, and improve rocker arm-to-valve cover clearance.

The Trick Flow GenX heads feature 65cc combustion chambers. I verified volume with a burette; and each chamber was spot-on at 65cc.

The decks are impeccably machined to a very fine RA finish, perfect for MLS gasket use.

Here is the cylinder head tightening sequence. The ten primary head studs are installed finger-snug, with nuts final torqued to 80 ft.-lbs. The inboard 8mm “pinch” stud nuts were torqued at 25 ft.-lbs. All threads, washers and nut undersides were coated with ARP assmebly lube.

The COMP Cams Ultra Gold rocker arms feature heavy duty valve tip rollers, high-durability caged-bearing trunnions, and a relatively low profile. The kit comes with rocker arm stands so a pair of rockers can be bolted directly to the heads. The stands feature radiused pockets that accept the rocker trunnions. Rocker arm ratio is 1.72:1.

Our Fluidampr harmonic damper features a 7.5” diameter pulley. The damper was carefully drawn onto the crank snout with an interference fit of 0.0015” (with front seal and snout lightly lubed).

Timing System

Our timing system is a Cloyes Hex-A-Just set. It includes the crank gear, chain, cam gear, oil pump drive gear, needle bearing unit and a cam timing adjuster bushing. The cam gear is compatible with a front-mounted (LS2 style) camshaft position sensor.

To install, position Number One piston at TDC, with the timing mark on the crank gear at 12 o’clock. Position the camshaft with its pin at approximately 3 o’clock. The roller bearing supplied with the set is installed between the cam nose and rear of the cam gear. The caged black side of the bearing must face the block so the bearing can rotate freely. The Hex-A-Just bushing is inserted into the cam gear from the rear of the gear. Install the cam gear and chain and verify that the timing dot on the cam gear is at 6 o’clock, facing the mark on the crank gear.

Hold the cam gear flush against the bearing and cam and finger-install all three cam gear bolts. Snug the bolts to eliminate any slop in the cam gear. Roll the crank back and forth, bringing it back to the gear alignment marks. Crack the three bolts loose just enough to allow gear adjustment. Use a 1/4-inch hex wrench to rotate the Hex-A-Just bushing to your desired cam timing. For now, we set this at zero. The cam timing was then checked using a degree wheel.

A chain damper helps control timing chain harmonics. Some LS blocks come with this damper, but our iron LQ9 block does not have bolt holes to install one. The damper adapter from Trick Flow features a bracket that shares the bottom three bolts for the camshaft retainer plate; the plastic damper bolts to the bottom of the bracket.

Cover Plates

The front timing cover is from COMP Cams. It can accommodate a front-mounted (LS2 type) cam position sensor and allows you to use a big block Chevy timing pointer. The hole for the cam sensor has an adapter plug with an offset hole for the sensor. The supplied square-profile O-ring fits on the adapter for sealing. If the block is stock and features a standard cam bore location, the adapter plug is installed with the sensor hole at 6 o’clock. If you’re dealing with a raised-cam block, the sensor hole should be positioned at 12 o’clock.

The front cover is supplied with black oxide socket head cap screws that nestle into the mounting holes’ counterbores. We decided to use 8mm ARP 12-point bolts. Since bolt head flanges were a bit too large to seat in the counterbores, we filled the counterbores with two small washers behind each bolt head. The bolt location behind the timing pointer adapter is too shallow for an ARP bolt head, preventing the timing pointer adapter from seating flush. You can grind a notch on the backside of the lower area of the adapter to fit the ARP bolt, or use a socket head cap screw. Since the adapter hides this fastener, we used the screw.

The rear engine cover (which houses the rear main seal) is a new OEM unit. Prior to installing the cover, we fit a new OEM plastic oil galley plug into the rear oil galley hole. After installing the rear main seal and the white nylon seal guide, the rear cover is carefully and squarely pushed onto the block, centering the crank flange to the seal guide. The guide prevents the rear main seal lips from folding rearward. Once the cover is fully inserted, the guide pops off.

Instead of using an ugly OEM valley plate, we made one from .250-inch thick 6061 aluminum. The cover is six inches wide and 23 3/8 inches long and fits flush front-to-back on the block. We bored an access hole in the left rear to clear the oil pressure sensor, allowing enough clearance to fit a 15/16-inch thinwall socket. The underside of the plate was CNC groove-machined to mimic the OE gasket path. The groove accepts a 3/32-inch O-ring strip to provide sealing.

There are two recesses in the casting at the top front of the block. We filled these in with All-Metal body filler to create a flat surface for the front of the valley plate. All-Metal filler is a high-density, aluminim-impregnated filler that is very hard and withstands block operating heat. The plate was installed using ten 8mm ARP 12-point bolts.

Cam Sensor and Timing Pointer

The camshaft position sensor fits in the offset hole in the COMP cover’s sensor adapter. The sensor O-ring was lightly lubed and inserted; the sensor’s mounting tab was secured to the cover with a 1/4-20 socket head cap screw. The timing pointer adapter included with the COMP cover adapter is drilled and tapped to accept any big block Chevy adjustable timing pointer. We fit a TCI timing pointer to the adapter with the 1/4-20 socket head cap screws included with the pointer. They were a tad long, so we shortented them by 3/16 inch.

An OEM cam sensor harness is required, available at any GM dealer. We removed the ugly steel bracket from the harness and covered the wires with black braided loom sheathing. We fabricated a small aluminum mounting plate with an Adel clamp to secure the harness to the front cover. The cover was tapped for a 10-32 cap screw, which secured the clamp to the mounting plate. The cam sensor harness should be plugged into the sensor prior to mounting the timing pointer. The harness can be connected with the pointer installed, but access is tighter.

The front oil galley hole was plugged with a new OEM expansion plug lightly coated with RTV prior to installation. The plug was tapped flush with the block surface.

Lifters

We used OE-style lifter guides for this build. The four plastic lifter guide trays have opposing flats to retain the roller lifters in plane with the cam lobes. Before installing the lifters to the trays, we drilled 5/16-inch oil drain holes on the outboard side of each guide tray. This prevents oil from puddling up inside the tray wells and flooding the lifters, The COMP Cams hydraulic roller lifters were coated with 30W oil and secured to the lifter trays. Each tray is mounted to the block with a single new 6mm shouldered bolt, torqued to 106 in.-lbs. (with medium threadlocker).

Oil Pump, Windage Tray, and Pickup

The Melling oil pump was secured to the block with four ARP bolts torqued to 18 ft.-lbs. Temporary 0.0005-inch shims were placed around the perimeter of the crank snout’s pump drive gear to carefully center the pump bore relative to the crank snout.

If you use a GM windage tray like we did, three of the eight bolt holes in the tray need to be enlarged to accommodate the ARP main studs, which measure 0.390 inch in diameter. Open up the three holes to 0.400 inch.

When using a stroker crank, install the tray and rotate the crank to check for interference with the connecting rod big ends. It’s common for the rod bolt heads to contact the tray. We fixed the problem by adding two 0.095-inch thick washers between the main cap nuts and tray at seven of the eight bolt hole locations. This provided us with about 0.100-inch clearance between the tray and rod bolts.

The left side area of the windage tray where the oil pickup tube bracket attaches to a main stud had to be clearanced to allow the pickup tube support bracket to align with the main stud and fully seat. This was done by hogging out the entire area where the tube bracket interferes, including the tray’s bolt hole. This allows you to mount the pickup tube bracket directly to the main stud with no spacers or tray material to alter the pickup screen height.

We used Holley’s cast aluminum oil pan with a black ceramic coating. The pan features a slightly deeper front pan area that clears a 4.000 inch stroke crank with no rod clearance issues. The Holley pan includes a baffle, pickup tube assembly, oil filter adapter, drain plug, and an oil cooler crossover cover (where an external oil cooler is not planned). The oil drain plug hole features a helical insert, which is a nice touch. Holley specifies an AC Delco PF48, Wix 57060, Mobil 1 M1-113, or equivalent oil filter for use with this pan.

Recommended oil pump pickup screen-to-sump-bottom clearance is 3/16 to 1/2 inch. The Melling oil pump includes two O-ring seals for the pickup-to-pump mount to accommodate different pickup tube designs. We used the thinner black O-ring with our Holley pickup tube.

The oil pan mounts to the block and front cover with twelve 8mm ARP bolts and flat washers. It is secured to the rear cover with two 6mm ARP bolts. All 8mm bolts are torqued to 18 ft-.lbs., while the rear 6mm bolts are torqued to 106 in.-lbs. Hole alignment on both the Fel-Pro gasket and Holley pan were dead-on, with no need to modify any pan holes. The pan’s oil cooler ports were covered with the supplied crossover housing, a Fel-Pro gasket, and two ARP 6mm bolts.

Cylinder Heads

The Trick Flow GenX® 225 aluminum cylinder heads feature 225cc intake/80cc exhaust runners and 65cc combustion chambers with Trick Flow’s full CNC Competition porting and chamber machining. Features include 2.055-inch intake/1.575-inch exhaust valves, dual 1.300-inch valve springs, titanium retainers, and seven degree locks. Trick Flow changed the valve angle from 15 degrees to 13.5 degrees to decrease valve shrouding, increase mid-lift airflow, and improve rocker arm-to-valve cover clearance. Material was also added at the rocker arm mounting points for increased high-rpm valvetrain stability. Spark plugs are angled to enhance mid-lift airflow.

We used Fel-Pro MLS Permatorque head gaskets. Orientation is critical to avoid blocking off water jackets, so each gasket has a prominent “FRONT” imprinted on the top front side. The heads were secured with ARP head studs. Prior to head installation, the 11mm female threads in the block were cleaned using an ARP thread chaser specifically designed for LS blocks. The ten primary head studs were installed finger-snug, with nuts torqued to a final value of 80 ft.-lbs. All threads, washers, and nut undersides were coated with ARP assembly lube. The inboard 8mm “pinch” stud nuts were torqued to 25 ft-.lbs.

In case you’re wondering about our static compression ratio, it ended up at 11.4:1.

Rocker Arms and Pushrods

While OEM powder metal rockers used with a trunion upgrade kit would certainly suffice for this build, we wanted to remove the friction factor between the rockers and valve tips. We went whole-hog and stepped up to COMP’s Ultra Gold ARC aluminum full-roller rockers, sticking with the OE ratio of 1.72:1.

When installing rocker bolts on an LS head, you must apply thread sealant to the intake rocker bolts as the threaded holes in the heads are open to the intake runners. Failure to seal these threads will likely result in a vacuum leak.

The rockers are non-adjustable, so pushrod length is critical. We used an adjustable checking pushrod, light checking valve springs, and a hydraulic lifter converted to solid to determine pushrod length. With valve closed and with the checking pushrod adjusted to zero, we measured a length of 7.450-inch. After adding 0.050-inch for lifter preload, final pushrod length came out to 7.500 inches. We used one-piece Elgin 5/16 x 0.110 inch wall pushrods.

With the light checking valve springs and solid lifter in place, we measured valve-to-piston clearance. It measured 0.190-inch on the intake side and 0.143-inch on the exhaust.

Harmonic Damper

The 7 1/2 inch diameter Fluidampr harmonic damper fits on the crank snout with a 0.0015 inch-plus interference fit. The crank snout was lightly coated with Royal Purple Max Tuff assembly lube, then the damper was carefully drawn onto the snout using a balancer installation tool. The damper was secured with an ARP crankshaft bolt to a final value of  235 ft.-lbs. (with ARP lube). The reusable ARP bolt is much stronger than the OE part and can be tightened directly to a torque value rather than mess with the multi-step OE torque-plus-angle process.

Flywheel Bolts

Be aware that LS crank flange flywheel bolt holes are open to oil, so a thread sealant is required on all flywheel bolt threads. We used ARP flywheel bolts with medium threadlocker sealant on the threads and a light coat of ARP assmebly lube under the bolt heads.

What’s Next

In Part Three of Nighthawk LS, we’ll cover the induction and ignition systems, sensor and water pump installation, and then jump into the dyno room and see what this puppy will do. You won’t want to miss it!

In the meantime, you can begin assembling your own Nighthawk build thanks to special Back in Black Nighthawk combos from Summit Racing.

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