Motor Trend on 3-valve OHV V8

[LMN8R]

From the November issue

"Beware, Dodge Viper and Ford GT. The 2006 C6 Corvette Z06's 6.3-liter Generation IV small-block push-rod V-8 features 24 valves and makes 500 horses at 7000 RPM. The Gen IV is the featured engine using a new GM powertrain technology: a three-valve/cylinder pushrod valvetrain, which the automaker also will use in some High Value V6s. The C6's small-block can grow to 7.0 liters and rev to 8000 rpm.

The new design pairs intake valves side by side; they're operated by a forked rocker arm. The exhaust valve sits on the opposite side of teh combustion chamber, with a centrally located spark plug in between. The Gen IV flows more are through its dual intake ports, and the intake and exhaust ports are more widely separated for less heat transfer from the exhaust ot the intake charge. The extra horses work well with the Displacement on Demand system that appears with the Gen-IV V-8 and High Value V-6's-more power means more opportunity for the engine to idle half its cylinders. Look for the deeper breathing heads and associated upgrades in the 2005 model year."

[LMN8R]

Some other threads have already eluded to this, but this is a different source, so I thought it'd be useful.

I was looking at the new 6.0 liter Ford PowerStroke V8 this weekend in a cutaway model that they had at the Kansas Speedway for the races. It has 4 valves/cylinder using a pushrod system as well. Instead of using forked rocker arms, the rocker arms push down on a "connector" or "bridge" that is in contact with its respective valves.

Sounds pretty cool to me.

-G

Great post. The way the MT article reads, to me it implies that all the Gen IV engines will be DOD. Seems logical. So, as some us have speculated before, the base vette will be significantky more powerful and DOD helps by keeping the vette below the gas gussler tax.

I hope the idle doesn't sound like a Honda.

[rrubel]

Hm. 6.3 liter. Is that a 427? They did say Z06... That'd be awesome.

Other manufacturers have done 3 valves per cyl (most notably Mercedes) but I cannot recall if they were pushrod or OHC engines. Seems to me that you should be able to angle the valves slightly (so that the tips come together in a V) and still use a single non-forked rocker arm. Then again, I thought the two main advantages of a multi-valve setup were a) lower weight for the same size openings and b) able to vary the timing of the two valves' overlap. Using a single pushrod and rocker kinda defeats that second one...

[RICHR]

Mercedes uses a SOHC and two spark plugs / cyl for the 3 valve 3.2 V6. Not sure about their otheer engines.

[Brett]

A 427 is a 7 liter engine.

A 6.3 liter would be like 390 cubic inches.



Brett