Catalog all the parts you remove: A box of bags and a Sharpie will make your life easier when you bolt everything back together. Drain the cooling system and save the coolant to be reused, remove the air cleaner, throttle and kick-down linkage, secondary wiring, and disconnect the fuel line, using a can or cup to contain the gasoline. You have the discretion of removing the carburetor or leaving it intact with the intake manifold. Pop the distributor cap, mark the position of the rotor on the firewall, free the primary wires from their hold-downs and at the spark plugs, and remove them with the cap. Pull the distributor and set it aside. Unfasten the intake manifold bolts. Since the manifold is likely well adhered to the cylinder heads, you may have to coerce it by inserting the tip of a large screwdriver (or the like) between it and the cylinder head, tap gently with a hammer, and pry it loose.
Carefully lift the manifold from the heads and set it aside. If the gaskets are stubborn, you will need a scraper to remove the dregs. Since we're going to replace the cylinder heads, there's no need to make sure that none of the gasket material disappears into the intake ports. Unbolt the headers or exhaust manifolds from either side of the engine. In most cases, they will likely be suspended by the exhaust system. Just make sure they don't compromise working room when you replace the heads. Unbolt the rocker arms and pull the pushrods out. Remove the cylinder heads. Stuff the cylinder bores with rags to keep out potential crap and make sure that the block deck surface is free from debris. Inspect the water and steam holes to make sure they are open and free to flow. Use a gasket scraper to peel intake manifold sealant residue from the block rails and apply solvent or something similar to clean the surfaces.
We used the package approach (components designed for the utmost in compatibility and function) for our intake manifold and cylinder head swap. The Edelbrock Performer RPM heads (PN 60739) and RPM Air-Gap intake are meant to complement one another. The complete heads feature 70cc combustion chambers, 170cc/60cc intake and exhaust port volumes, and 2.02/1.60 valves. On the flip side, the Performers employ a 1.45-inch valve spring diameter, 3/8-inch rocker studs, and a 0.575-inch diameter pushrod.
Note subtle differences between the used head gasket and the new Edelbrock 7310 replacement. Upper steam holes are larger and the sealing beads around the cylinder holes are much more prominent. These shims are 0.041-inch thick and help the motor to realize about 9.50:1 compression ratio.
The big steam hole in the existing block (a '68 327) was non-existent. To help cool the motor better, John Barbera taped off the opposite cylinders (to keep metal filings out) and used the new gasket as a template and installed it using the register dowel pins at either end of the deck. To begin the hole enlargement, he centered a drill punch and whacked hard enough to leave a sharp indent for the bit.
To finish drilling the hole, Barbera used a 0.250-inch bit, which was a little smaller than the opening in the gasket. No foolin' here, he simultaneously applied a high-powered shop vacuum to avoid the flashing as he drilled...
We now have a 7/16-inch hole drilled to allow the correct amount of coolant flow. Instructions to do this are also described in the Fel-Pro (PN 1003) head gasket installation kit.
Before installing the new heads, it's a good idea to run a thread chaser in the head bolt holes to free them of debris that might give a false torque reading. Lay the gaskets on the block deck, using the dowel pins to locate them properly. Install the cylinder head gently but firmly on the pins and screw the head bolts in place.For a measure of safety and reliability, John employed ARP High Performance Series cylinder head bolts (PN 134-3601) which maintain strength of 170,000 psi (15-percent stronger than Grade 8). Hardened parallel-ground washers complete the set-up.
John ran the torque sequence as per the factory shop manual and without lubing the threads until he reached the specified 65 lb-ft.
Upper valve rain pieces go on next. After lubing the ends of the Comp Cams Magnum pushrods (PN 7693-16), John dropped with into the lifter cups. The hardened pushrods are 5/16-inch in diameter, have a wall thickness of 0.080-inch, are 7.900-inches long (0.100-inch longer than stock), and designed to be used with guide plates. The Comp Cams Pro Magnum 1.52:1 roller rockers (PN 1301-16) are made of 8650 chrome-moly steel, but carry 5-percent less weight at the valve train than most aluminum rockers. They also boast a lifetime guarantee.
The sleek Permastar finish on the RPM Air-Gap intake manifold (PN 75012) is unaffected by heat and all corrosive solutions. Further, it includes rear water outlets, two distributor clamp locations, and bosses for nitrous nozzles. John put it to bed with Edelbrock 7201 gaskets and ran the proper torque sequence. Then he installed the 180-degree thermostat under the new water neck.
An Edelbrock 750-cfm Performer carburetor (PN 1411) completes the combination. It comes with .113 primary and .107 secondary metering jets, .075 x .047 metering rods, and an orange step-up spring. Drop in the distributor, cap and wires, thermostat and water neck, fuel line with a proper filter installed prior to the inlet side of the carb, throttle linkage transmission kickdown, and sensor wires. Reconnect the coolant hoses fill the radiator, crank up the motor, and check initial timing.