We left off last month having just begun the 409 assembly process. The crankshaft is installed, and the remaining components are ready for final assembly. We had to send the connecting rods to the local machine shop to have the new ARP Wave-loc high-performance rod bolts (PN 134-6403) pressed into place, and then have the rods resized to be perfectly round. Now it’s time to get this barn-fresh W-engine updated to modern standards by installing a set of Edelbrock Performer RPM aluminum cylinder heads, and a complete roller valvetrain setup from Comp Cams.
Updating a 409 engine these days usually involves a stroker crank and modern low-profile pistons, but we chose to retain the stock bottom end, as it had survived many years of abuse on the dragstrip, and we figured it would withstand our abuse as well. The advantage of the modern rotating assembly is reliability, especially at high rpm. With the stock bottom end, our ceiling for rpm is around 6,000, due to the very heavy piston design and weak connecting rods. A stroker build, even with a lower compression ratio, would gain at least 50 hp, and it would let us turn the engine higher. If we were seeking all-out horsepower, we would’ve certainly gone the stroker route, but that would’ve required machining the flawless block. Our decision was to retain the stock rotating assembly, in spite of leaving horsepower and reliability on the table. Wish us luck—we might need it!
Although the bottom end is stock, we updated the engine with a set of Edelbrock Performer RPM aluminum cylinder heads. These heads are half the weight of the original iron castings, and the ports are designed to flow 273 cfm (intake) and 216 cfm (exhaust) at 0.600-inch lift, which is where our camshaft maxes out. The cylinder heads have the stock valve sizing of the popular “690” heads, which were used in 1962 and 1963 high-performance 409 engines—intake valves measure 2.19 inches and exhaust valves measure 1.72 inches. Why would Edelbrock make a set of aftermarket heads and keep the stock valve size? A larger set of valves would require machine work on the block and piston, as the unique combustion chamber design creates tight tolerances, even with the 2.19/1.72 valves. Edelbrock wanted its heads to be true bolt-ons and did its homework to make that concept a reality. Our stock 409 short-block required no preparation for the new cylinder heads.
We ordered the Edelbrock 60815 heads, which came complete with valvesprings designed for a hydraulic roller camshaft. This brings up another way of updating our barn-fresh 409 to modern standard—a hydraulic roller camshaft and valvetrain. We called the folks at Comp Cams to help us determine the appropriate profiles for this engine, making sure to have all the horsepower ramped in before our rpm ceiling of 6,000. The end result is a camshaft with 236 degrees of duration on the intake side and 242 degrees on the exhaust side at 0.050-inch lift. Maximum lift is 0.578/0.593, which is right at the limit of our valvesprings. We used Comp Cams’ retro-fit link bar roller lifters (PN 8959-16), as they are a direct drop-in product with no modifications necessary. We added a set of Comp Cams Ultra Pro Magnum roller rocker arms (PN 1620-16), which feature a chrome-moly construction and a 1.7:1 ratio.
Our updates will result in better airflow, smoother valvetrain operations, and lighter weight, all of which equals horsepower. The new combination is designed to work with our stock rotating assembly, and it should make peak power right before our 6,000-rpm limit. Be sure to check out next month’s installment of “Unearthing a Legend” to see the finishing touches on this historic 409 and exactly how much power it makes on the dyno.
1. When we left you last month, we had installed the ARP main studs and the original forged crankshaft into the 409 block. The remaining components in the rotating assembly can now be installed.
2. We’re using the original pistons, which are GM 3819377 units. These forged units are original for high-performance 409s and provide an 11:1 compression ratio. We used a ring groove cleaner before installing the rings.
3. While many engine builders rely on file-fit moly rings for high-performance builds, we went back to the basics with a set of Hastings steel rings. We slid them into place, making sure there was no binding.
4. Show Cars Automotive sells a 409-friendly ring compressor, so that’s what we used for our build. Otherwise, you must carefully feed the rings in by hand, because a standard ring compressor will not work with the odd angle of the deck surface.
5. Once the pistons were tapped into the cylinders, we made sure the connecting rod was seated firmly against the journal. We then installed the rod caps, and brushed some ARP Ultra Torque lube on the threads to ensure proper torque specs.
6. Heavy weight motor oil was used to pre-lubricate the Clevite rod bearings during assembly. We tightened the ARP Wave-loc rod bolts to 55 ft-lb using the Ultra Torque lube. Always refer to original torque specs when using original-style rod bolts.
7. A standard oil pump slides over the ARP stud, and will provide sufficient lubrication for the 409. After the pickup tube was test- fitted and adjusted, we tack-welded it into place.
8. The ARP main stud kit came with extra-long studs for the windage tray and eight nuts to install the tray. Red Loctite is used on the studs to prevent the nuts from backing off.
9. Four of the eight nuts with the kit are used as a base for the windage tray—the base nuts are installed upside down to take advantage of the shoulder. Then the four retaining nuts are installed and tightened.
10. If you’ve ever dealt with a 409, then you know the struggle of finding a decent oil pan. Reproduction pans are available, but a factory pan is much stronger to prevent leaks. We found this one at a swap meet for $200. Oil capacity is 6 quarts.
11. The Comp Cams hydraulic roller camshaft and retrofit link bar lifters are very important factors in updating this 409 engine. The camshaft profiles offer a broad horsepower range, and the roller configuration certainly frees up a few horsepower.
12. As we prepare to install the camshaft, it is important to note the two plugs just above the camshaft bore. These oil galley plugs were originally pressed into place, but you can have your local machine shop drill and tap them to install threaded plugs.
13. Before sliding the camshaft into place, we coat the lobes with Cam & Lifter Installation Lube from Comp Cams. As we prepare to install the camshaft, we also coat the journals and cam bearings with heavy weight motor oil.
14. As the camshaft is installed, you should feel a slight bit of resistance each time a journal passes through a bearing. If the camshaft binds, do not force it, as this could result in bearing damage. If you do not have a camshaft installation tool, you can bolt the sprocket to the end of the camshaft to provide more leverage.