When we left off last month, our short-block Chevy engine was assembled and we had determined what we needed to look for when it came to cylinder heads (67cc combustion chambers). Half the valvetrain components were also in place (cam and lifters) but we still had yet to choose rocker arms and measure for pushrods. In addition to determining those components, we also needed to check the piston-to-valve clearance once the cylinder heads and related valvetrain components were on-hand.
To top off our budget build, we chose a pair of Summit Racing cast-iron Vortec cylinder heads due to their reputation for being a great out-of-the-box design at an even greater price. The Vortec cylinder head design dates back some 30 years, but its cutting-edge design (for the time) still retains great performance characteristics, even putting many aftermarket heads to shame. Keeping with the updated/upgraded trend, we’ll be complementing the roller lifter/cam setup with a set of Summit cast-steel roller rocker arms, another great, budget-friendly upgrade.
Here’s our short block, ready to accept cylinder heads and valvetrain.
While we were conscious to choose components that were friendly to the wallet, one thing that we did splurge on were component fasteners from Automotive Racing Products (ARP). Their fasteners are second to none, so it should come as no surprise that we chose to spend a little extra coin for those fasteners that count, namely main bolts, head bolts, and rocker studs.
We’re putting a bow on the assembly portion of our long-block Chevy, but we’re by no means finished as we still need to dress the engine up and equip it with the proper induction and ignition components before we head out to the dyno to see what our shorty Chevy will make.
ACP
Sources:
Automotive Racing Products (ARP)
(800) 826-3045 arp-bolts.com
We opted to go with a set of cast-iron Vortec cylinder heads from Summit Racing (PN SUM-151124) to take advantage of their efficient design and budget price. Thanks to 1.940/1.500-inch valves, “double-quench,” controlled-swirl combustion chambers, and high-velocity laminar flow, these iron heads will outflow many traditional, aftermarket head designs.
Deck height, valvetrain components, and cylinder head specs all affect pushrod length. To ensure proper rocker geometry it’s necessary to measure the actual pushrod length and order a set to spec. A Comp Cams Hi-Tech Pushrod Length Checking Tool Kit (Summit PN CCA-7705) is invaluable for this process.With one cylinder head torqued in place, one of the adjustable pushrods is installed along with the rocker arm. With the lifter on the heel of the cam, the pushrod length tool is adjusted until the tip of the rocker is close to the center of the valve stem. Each revolution of the pushrod tool equals 0.050 inch, so final length is easily determined by counting the number of rotations and adding that to the tool’s indicated length; 7.300 inches in our case. A set of Comp Cams Hi-Tech Pushrods (PN CCA-7949-16) were then ordered.
With the pushrod length determined, we can now check the piston-to-valve clearance. This simple test will ensure there is plenty of real estate inside the combustion chamber between the valves and the pistons. Given the relatively conservative cam specs and fairly large combustion chamber, there’s really no reason to expect any issues to arise on our setup, but it’s good practice to check things just to be safe. A lump of model clay is placed over the valve reliefs of one piston …
… then the cylinder head is installed, torqued to spec, and both valves adjusted on the number one cylinder only.After a couple revolutions of the engine, the head is removed and the clay is trimmed and inspected.Summit Racing recommends a minimum piston-to-valve clearance of 0.080 inch on the intake side and 0.100 inch on the exhaust. As you can see, we’re well within those minimums.Hardware for our cylinder heads and valvetrain components come by way of Automotive Racing Products (ARP). A cylinder head bolt kit (PN 134-3703) will ensure the heads stay firmly in place while a set of rocker arm studs (PN 134-7101) provide extra height for the Comp Cams pushrod guides (Summit PN CCA-4808-8).Our ARP head bolt kit includes polished stainless steel 12-point external fasteners and black oxide chromoly 12-point fasteners for those inside the valve covers. Many of the head bolt holes intrude into the coolant passage in the engine block, so it’s necessary for those fasteners to receive a liberal amount of ARP Thread Sealer.Those fasteners installed in a blind hole receive a dab of ARP Fastener Assembly Lubricant on both the threaded portion as well as under the head of the fastener for accurate torque ratings.Here, our assembled Vortec heads are installed, torqued to spec, and ready to receive pushrods and rocker arms.To keep within our “budget build” guidelines, we chose this set of rocker arms from Summit Racing (PN SUM-141706PL). The cast steel construction keeps the weight down, while the roller tip will provide smooth, friction-free operation.We went through and adjusted all the intake valves before starting on the exhaust valves, but the process is the same regardless. First, the engine is rotated so that particular lifter is located on the heel of the cam. Next, the rocker arm nut is tightened until a zero-lash state is achieved (slight friction felt by spinning the pushrod).The rocker arm nut is then tightened an additional half-turn …… before the polylock is tightened, effectively locking in the valve adjustment.No, this isn’t a scene of a valve adjustment gone bad, that’s Comp Cams’ Cam and Lifter Installation Lube (Summit PN CCA-153) applied to any and all moving surfaces of the valvetrain to ensure proper camshaft break-in is achieved.
Here’s a cleaner version of our assembled long-block ready for a few dress-up components, ignition, induction, and a trip to the dyno for break-in and final numbers.
