Oldsmobile’s Infamous W-43

Don’t Call Me a Hemi – ’cause I’m not!

hemi 455This is both a sad and an enervating story. It is a “what might have been”, but it is more than that . . . it is a story about a huge engineering breakthrough in street muscle car head design, not so much because of its 4-valve heads (At the time, Ford Indy engines were running a similar setup) but because they were pushrod activated, and yet compact enough to fit in a standard GM A-body chassis. (Of course 525-550 HP on pump gas isn’t a bad deal either).

This engine was to be the answer to the 426 Hemi, the LS6 Chevy and the SOHC 427 from Ford. They built this baby, but GM shut them down. Did they have the other guys covered?

You bet they did.

Read on to see how Olds did the impossible . . .

In the late 60’s and early 70’s, when cubic inches and horsepower ratings in excess of 400 ruled the day, the factories were always trying to wring more from their existing pieces. The practice was to get an efficient engine and then increase the displacement when more power and torque was needed. But engines still seemed to have a practical limit of about 500 cubic inches. By 1968 the factories had hit that wall, with all manufacturers settling at about 440-460 cubic inches as practical for a passenger car engine.

Most street pieces could reach about one horse per cubic inch with existing OHV setups and a good camshaft and carburetors. More horsepower was available, but it required radical camshaft timing and induction systems that were not truly compatible for street use. They made impressive HP, but they were not a car one could drive on a daily basis.

So what do you do after hotter cams and more carbs can’t get any more tractable horsepower? Oldsmobile’s response was valves – 4 of ’em. Olds engineers had been one of the first to install a flow bench at experimental engineering. Going back to the early 60s, they had studied airflow and combustion chamber configuration – way before anyone else was even thinking about it.

It is a little known fact that the reason why the stock Olds V8 engine survived so long in the GM lineup is because the combustion chamber was the only one that could meet emissions requirements without port fuel injection – hence all those carbureted 307s hanging on for as long as they did.

So it’s no surprise that Olds engineers were looking for a way to get better breathing without the use of radical cams and huge ports (something that they knew would kill idle and smoothness) but yet result in good HP across the rpm band. The question was whether they could they build a set of heads that could be used with existing short block components and be manufactured in mass production. The result was what you see here, the W-43 high performance engine – slated for release in 1971- 1972.

With a mild camshaft, the engine made an easy 500 HP and 535 ft lbs of torque. With a radical street cam, 550 HP was simple. It was so healthy that Olds considered going back to 400 cu. in. for street use. Designated W-43, this engine’s mile-wide valve covers hint at the then modern science that resides within. No aluminum race motor, it was cast in iron, like its earlier 455-cubic-inch production counterparts

To make those numbers, the engine only needed its pent-roof combustion chambers, four valves per cylinder, an 800 CFM four-throat Quadrajet carb, special-cast crankshaft, forged-steel connecting rods and 10.2:1 CR pistons.

According to Oldsmobile engineering sources, the W-43 engine was the one powerplant in their experimental series that came closest to actual production. It was slated for the 1972 model year. When Uncle Sam enforced the unleaded fuel rule, Olds built another prototype with lower compression and found it only lost 10 HP!

If you study the photos carefully, you will see that the motor was not only ready for road use, as it sported all components in the proper place, such as brackets, and gaskets. And you can also see the evidence of run-in on the parts. This was no dyno queen; this was a road test beauty. Rumor has it hat a certain silver 71 W-30 was blowing the doors off of some heavy Detroit iron on Woodward Ave, late at night, but the hood was never lifted. Could it be?

Considering the intended use. the block was also a special unit, though externally, there was no noticeable difference. Strengthened in all the right places, especially around the main saddles, it even sported 4-bolt mains! (See photo).

But it was not to be. After many miles of dyno and street driven testing, Olds pulled the plug on the motor. Many later blamed the death of John Beltz, Oldsmobile’s then pro-racing General Manager, but what killed the engine were two things, the recognition of the upcoming EPA rules that this gas guzzler couldn’t meet; and the consternation (read screaming) from Chevrolet.

Olds did consider the engine for an across the board application for passenger car use, with slightly smaller valves and a tamer cam. Results were good, with 15-20% better torque and HP across the RPM band, but the cost to produce the heads versus the stock 16 valve pieces killed that idea. In many ways, it’s a shame, because Olds could have run the heads on the 350 and likely increased performance and mileage 10 years before Detroit got on that bandwagon.

Look closely at these photos, especially the cylinder head. Note the stock gasket impression, the run in valves, and the fact that water jackets and mounting bosses were in place. It is obvious that they were ready to be production pieces.

In the case of the W-43, each intake was 1.75 inches across, while the stainless-steel exhausts were 1.375 inches in diameter. The Olds followed the then Cosworth-Ford Formula One practice of a 37 degree angle between the valves. Locating both exhaust valves directly opposite the intake valves allowed this central spark plug location.

Taken individually, each valve is considerably smaller and lighter than the units that would be needed to equal the airflow potential of a conventional two-valves-per-cylinder arrangement. Despite having almost twice as many components, efficient design and production parameters kept these heads’ reasonably compact.

The cut-away cylinder head section illustrates the shallow valve angle and the extensive coolant jackets surrounding the valves. Good chamber design called for a maximum ignition timing of only 29-30 degrees, while production 455s called for a more conventional 37-38 degrees of lead. This alone could have resulted in much better fuel mileage, if tuned for economy rather than performance.

The intended production pushrod head casting used an outer spring with an inner damper. Note the huge oval-shaped inlet ports, similar to those familiar with the current 4-valve Ford Mustang Cobra and the Caddy/Olds 4-Cam.

Considering the complicated rocker arm design, the assembled rocker assembly was very compact. The picture of the head shows the early layout – with iron rockers, but with Swedish chrome-silicon steel valve springs. Vertical tubes between the shafts are typical of today and are for access to the spark plug.

Originally rocker arms for the W-43 engine were cast iron. Because of the location of the pushrod arms at the extreme outboard end of each rocker body, there was excessive friction at the shaft pivots, which was discovered in both long dyno run-ins and street testing. This caused a switch to the aluminum units shown. These later forged aluminum alloy rockers pivoted on needle bearings to reduce friction and allow less parasitic HP loss.

The aluminum pieces also had a steel insert in each pushrod adjustment socket to resist wear. the valve adjustment arrangements were also unusual – more like a race piece. When the aluminum units replaced the iron pieces, the engine revved well past its usable rpm range!

This view of W-43’s valley illustrates how the intake ports were pushed together to make a clear path for the pushrods. Fortunately these intrusions at the sides of the ports, just upstream of the valve pockets, and might appear restrictive. But with 3.1 square-inches of port cross section remaining even at the tightest point, intake flow was down just 20 percent in comparison with the non-pushrod DOHC OW-43 engine (again, another story). Note production stamped steel intake manifold gasket.

The W-43’s exhaust manifolding was flow-tested and streamlined for both chassis clearance and efficient exhaust gas outflow. Castings were made with either 2 1/2 and 2-inch outlets. The tube extending over the valve cover was for exhaust gas heat to the carb. Street features such as this indicated the powerplant’s readiness for production. Note part/casting number on the manifold.

It is a shame that both the new regulations from Washington and the public’s outcry on the horsepower race forced Olds to abandon this engine. With more development, it could have helped GM get a jump on their competition. As it was the lessons learned from the W-43 and the OW-43 did allow Olds to easily develop the Quad 4 and the Aurora V8.

The W-43 was the only big-block produced by Olds with 4-bolt mains.

The 4 valve head: Top – very compact designe for a pushrod, 4-valve design.

The 4 valve head: Bottom – The combustion chamber. Note central spark plug and space between valves for good breathing.

A cutaway of 4-valve head. Note good ports, angle of attack.

The combustion chamber. Note central spark plug and space between valves.Two Intakes @ 1.75″; Two Exhausts @ 1.35″.
NOTE it is a pent roof design, the chambers are NOT hemispherical.

An assembled head. Rocker stud & head bolt holes are unencumbered and valves have room for good-size springs. Note that the head is large, but more compact than the contemporary “Hemi”.

Head and block, showing the unique cam carrier that moved the cam higher in the block. This gave the pushrods a better angle of attack to the valves. Note intake gasket, which appears to be a production piece.

Special pistons were also needed to maintain proper compression ratio and flame travel. Flat top pistons were tried @ 9.5:1 and only saw a 2-4% loss in HP, no loss in torque.

Early and late design rocker arms shown. They were interchangable from side to side and intake to exhaust. NOTE that they are much shorter and more compact than Hemi style rockers because the pent roof allowed the valves to be inclined at a smaller angle.

Assembled engine, driver’s side, showing unique heat riser for carb. (Nothing is marked “EA” for “experimental application”. This is a prodution piece).

Assembled engine, passenger side, note casting number on what appears to be a production exhaust manifold. Shows thought to race applications where heat could easily be blocked off.

Engine in an A-Body frame – mocked up for fitment. Note there is plenty of room of the exhaust manifolds, a testament to the narrow 4-valve heads.

Source: Wild Auto Cars, By Bob Gerometta

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