We’ve arrived at the final installment of our 422 cubic inch small block Chevy build. You know what that means—dyno results!
You can cheat and scroll down to find out how well the engine performed, but then you won’t learn about the ignition system or accessories like the vacuum pump. The story’s not that long, so why not read the whole thing?
Here are the links to the first two articles in case you missed or need to reference them:
Want to build a 422 Chevy small block like this one? The folks at Summit Racing made some parts combos to help guide you. You can get more details on the Birchwood Automotive Small Block Thunder 422 parts combos here, and see the exact contents of each combo by clicking the links below:
Small Block Thunder 422 Chevy Short Block Combo
Small Block Thunder 422 Chevy Oil System Combo
Small Block Thunder 422 Chevy Top End Combo
Small Block Thunder 422 Chevy Ignition System Combo
Small Block Thunder 422 Chevy Completer Combo
Now, on with the story…
Crank Trigger & Distributor
I installed an MSD Flying Magnet crank trigger kit for increased timing accuracy. An aluminum trigger wheel with four imbedded rare earth magnets mounts to the face of the crank balancer. A pickup sensor mounts to the block; the pickup receives crank position signals as the crank rotates. Picking up the timing signal directly from the crankshaft eliminates the potential variables such as distributor gear backlash, wiggle, camshaft end play, etc.
The pickup has an adjustable bracket that offers about 20 degrees of timing adjustment. Place the pickup in about the center of its adjustment range, mount the wheel so that a magnet is as close as possible to the pickup, and adjust the pickup so it aligns exactly with magnet. Make sure that the arrow engraved on the face of the trigger wheel faces outboard. Installing the wheel backwards will allow the engine to fire but will cause false triggering at high rpm.
Once everything is installed properly, ignition timing is easily adjusted by moving the pickup in its slot to fine tune ignition advance. Adjust the air gap between the tip of the pickup and the edge of the trigger wheel to 0.050-0.080 inch; I set ours at 0.065 inch.
Since the MSD Flying Magnet crank trigger does not use the distributor for timing adjustment, I used an MSD Pro Billet distributor with the mechanical advance locked out. I also used an MSD bronze distributor gear that is compatible with the gear on the COMP Cams solid roller camshaft. A set of MSD Super Conductor 8.5mm ignition wires cut to length finish the ignition system.
Rather than installing crankcase breathers in the valve covers and relying on passive evacuation of crankcase pressure, we installed a Jones Racing belt-driven vacuum pump. An external vacuum pump provides a number of benefits including reduced friction; improved piston ring sealing by relieving crankcase pressure under the rings; reduced windage around the rotating assembly; improved oil scavenging; and reduced oil contamination. Using an external vacuum pump can also provide power gains of 10 to 35 horsepower.
The Jones two-stage, gear-style vacuum pump has built-in heat sinks that allow the passage of oil, fuel or moisture without damaging the pump. The two -12 AN inlets connect to the front of each valve cover via 90 degree hose ends and braided hose. The -12 AN exhaust port routes to a remote vacuum pump breather tank.
A multi-part drive hub assembly attaches to the crank balancer and registers on the MSD trigger wheel to provide a center register for the drive hub. The pump’s 0.500 inch thick mounting bracket sandwiches between the block and the MSD crank trigger pickup bracket. It caused the pickup to move 0.500 inch forward of the trigger wheel, so it was necessary to mill that much material from the rear of the MSD bracket in order to maintain the pickup sensor alignment with the trigger wheel.
18 degree cylinder heads require special valve covers with rails that provide wider inboard-to-outboard wall dimensions to clear the rocker arms. The mounting bolts pass through the valve cover roof instead of the outer flange. I chose Moroso fabricated aluminum valve covers and installed them with Fel-Pro reinforced silicone gaskets and 1/4 inch studs.
The valve covers have no breather holes so you can modify them to suit your requirements.
Since I’m running a Jones Racing vacuum pump and sealing the crankcase, I outfitted the valve covers accordingly. I created an oil filler on the left cover by drilling a 1.800 inch hole and TIG welding a female threaded bung topped with Earls threaded fill cap. The front wall of each valve cover was drilled and fitted with Earl’s -12 AN weld-in fittings so I could plumb the covers to the vacuum pump.
I used a Jones Racing one-wire alternator rated at 80 idle/140+ max amps and driven by the crank hub that also drives the vacuum pump. The unit mounts to the left side of the block with a Jones two-piece bracket assembly and a rear support.
I always use an aluminum electric water pump on my engine builds. This eliminates the need for a pump belt and the resulting parasitic drag on the crank while providing consistent high coolant flow. For this build, we chose a Meziere 300 Series pump rated at 55 gallons per minute of flow, The pump mounts to the block using Fel-Pro gaskets and four 3/8-16 x 1-1/2-inch bolts
We only had one session on the dyno, and the engine made 735 peak horsepower at 7,100 RPM and 575 lbs.-ft. of peak torque at 6,250 RPM. I’m confident that further tweaking would likely gain another 10-15 horsepower. Check out the chart below.
Birchwood Automotive 422 Chevy Dyno Numbers
|Corrected Horsepower||Oil Pressure