by John Carollo
(Taken from How to Rebuild & Modify Chevy 348/409 Engines by John Carollo)
While the 348 and 409 engines are more than 50 years old, the classic W engine is enjoying a renaissance. To raise performance, you need to improve airflow through the head, and a number of new aluminum high-performance castings are being offered from W-engine performance leaders Lamar Walden, Edelbrock, and Bob Walla Racing.
A steady stream of aftermarket parts was offered to hot rodders and racers upon the W engine’s release, and these high-performance offerings didn’t slow down much after Chevrolet benched the 348 and 409 in 1965. People kept building their beloved W engines in their stock, hot rod and race trims. Long-time W engine specialists Lamar Walden and Rich Rojeski released a set of CRW heads in the early 1990s. But in the late 2000s, a number of manufacturers tooled up to meet the evolving market demands for W engines. But the W-engine market was gaining terminal velocity in the mid-2000s. Specifically, Edelbrock debuted its Chevy 409 in the RPM Performer Series at SEMA in 2007 and in the same year Bob Walla Racing released its high-performance 409 head. In reality, more people were interested in building high-performance street engines and there was an increase in the popularity of nostalgia drag racing. As of this writing (2011), every part of a W engine has been faithfully reproduced, so a new generation of 348/409 engines can be built exclusively from aftermarket parts.
The CRW heads also retain mounting bracket holes similar to OEM units. Note the exhaust ports on the left and how they project outward. This CRW head is based on the famous 690 Chevy head, with improvements such as aluminum construction and better flow. Because the bolt pattern matches Chevy’s pieces, it is a bolt on and can be used with OEM and aftermarket intake manifolds.
In the case of aftermarket W- engine heads, two people stand out amongst the 409 crowd because they are 409 fans first and developers of serious, hardcore 409 parts second. Rich Rojeski and his brother Con coordinated with 409 expert Lamar is Walden to develop heads for the 409. Rich was a pattern maker and Lamar is a talented machinist and engine builder. The Z11 heads were the best flowing and horsepower-generating W-engine heads Chevrolet ever made. But they came at a time just before the factories and aftermarket started making aluminum heads. Intakes, yes, but heads not just yet. And with Chevrolet and General Motors halting their racing programs in early 1963, if any aluminum heads were in fact on Chevrolet’s drawing boards, they never made it off the paper. In 1992, Rich and Lamar’s new CRW heads were 356 T6 aluminum versions of those rare Z11 heads and came out of the molds to make their way to Lamar’s for machining.
This CRW head is based on the famous 690 Chevy head with improvements such as aluminum construction and better flow. Because the bolt pattern matches Chevy’s pieces, it is a bolt-on and can be used with OEM and aftermarket intake manifolds.
The airflow around the valveguide bosses has been improved and the heads have a 1/4-inch higher valve cover seat. The end result were two heads based on Chevrolet’s best street head, the 690, but with a number of performance upgrades including some that came from the Z11 head and being cast in aluminum. And, as matching heads to an intake is critical, a matching intake was also made specifically for these heads. The most important part of making a head is how it will flow and the CRW 690 head flows great. They flow better than stock, Chevy 690 heads, mostly due to the smaller radius of the raised ports of both the intake and exhaust. They are taller with a stock 690 having a measurement from deck to top edge of 3-15/16 inches and the CRW 690 offering 4⅜ inches. CRW 690 heads can use intake valves up to 2.50 inches.
The other CRW head is called a 690Z as it starts out the same as the CRW 690 and even looks identical on the outside. But inside, the CRW 690Z head moves the position of ports to Z11 locations. The spread between valves on a stock Chevy 690 head is 2.065 inches. The CRW 690Z head is 2.190 inches and that allows for the use of bigger valves.
To cover the distinctive heads CRW has made, a set of cast-aluminum valve covers was also cast by Rojeski and fits all three heads he and Lamar are involved with.
Bob Walla Racing
Bob Walla of Bob Walla Racing (BWR) developed aluminum heads for 348/409 engines because of pent up market demand. He came out of the box with two styles of 409 heads. One is based on the 690 version, which is one of the best production heads Chevrolet made, while the other is a raised-port version of the same head. Chevrolet never made such a head and it’s a product of Walla’s own history running 409s and racing with others who praised the engine design. BWR released both styles of heads in 2007 and it doesn’t take a lot of searching to see the letters “BWR” on the heads of fellow 348/409 racers and hot rods.
Bob Walla aluminum heads show very little metal between the two valve seats for the use of bigger valves. On the intake side of the head, note the intake port almost spans the width of the head. On the top of the head, note the strong bases for the screw-in studs.
BWR raised port heads have been reworked on both the exhaust and intake sides. On the outside, the two center exhaust ports have been raised to increase flow and also line up with the two outside exhaust ports. Along with the better flow, this makes header building a little easier as the exhaust flange ports can now run in parallel series. On the inside, BWR raised-port heads offer intake ports that are all raised by 3/4 inch. Although that makes them actually shorter in length, they are now better positioned for much straighter and faster flow from the intake to the valves. Typically, these heads offer an 18 to 20 cfm faster flow.
Bob Walla racing aluminum Chevy 409 shows some very large intake and exhaust valve ports.
Industry giant Edelbrock created the latest W engine heads, which have received a healthy share of attention in the aftermarket world. The Performer RPM 409 heads are cast from high-quality T356 aluminum and weigh 31.5-pounds each—half that of a Chevrolet W iron head. Sold completely bare or assembled, they’re based on the 425-hp version of the 409 head and include numerous improvements not seen on the original Chevrolet heads.
RPM Performer 409 heads offer swirl polished, stainless-steel valve sizes of 2.19 on the intake and 1.72 inches on the exhaust. By comparison, a stock 348 uses valves that measure 1.94/1.65 inches so the upgrade is substantial. Edelbrock uses hardened valve seats for use with unleaded fuel so street use of these heads is very much possible.
The intake ports of the Edelbrock head in detail. No surprise, the Edelbrock head far outperforms the stock iron head. It features CNC port-matched 220-cc intake and 115-cc exhaust ports. If you’re going to build a high-performance street or a race engine, you should start with an aftermarket block that can handle more than 600 hp and then go with a suitable set of high-flow heads, such as the RPM Performers.
The RPM Performer heads flow at 285/222-cfm at .700-inch lift literally right out of the box. The wall thickness of the ports on these heads is liberal enough for engine builders wanting more flow or to be able to tune that flow. Those ports are vastly improved over OEM units by one simple operation. The original ports use a harder angle as they turn toward the valvestems. Edelbrock used a smoother approach that increases flow to the cylinders. As CNC machines machine almost all of the aftermarket heads these days, those machines were used to step cut the ports for a good basic flow that easily exceeds the OEM pieces.
The Edelbrock head from the top side shows screw-in studs, push rod guide plates and valvesprings in deep pockets, and of course, this design supports the production of horsepower. The stock heads came with pinned-in rocker studs and didn’t have guide plates. Today, most of these features are standard equipment on aftermarket heads.
Other features include the use of steel threaded inserts, exhaust header bolt holes and rocker studs. All the holes in the block are drilled and tapped (when needed) as part of the precise CNC work on the block. And speaking of bolts, Edelbrock also offers its own head bolt kit that consists of high-grade bolts and hardened washers. Pipe sealant is needed because the bolts often go into the water jackets of the block.
Edelbrock also created its matching RPM Performer dual-quad intake manifold and that is detailed in the induction chapter. Keeping for a family of W parts, Edelbrock also made two versions of cast-aluminum, finned valve covers. They come in a black powder coat or polished finish. Neither use PCV nor oil fill openings, so an intake manifold with an oil tube is needed. The valve covers fit OEM 348/409 heads except for Z11 versions.
This aluminum head has been taken off a race engine to replace a few valves. Note the carbon deposits and how they do not appear in the lower part of the head. This indicates more of the fuel burning takes place close to the spark plug and on the top and center of the piston face. In the case of W engines, the top of the cylinder has a slight oval shape.