Gear Driven Overhead Cam Engines

[Shel_B]

I have some vague memories of gear-driven overhead cam engines, maybe from back in the 60s. Are there any such engines being used/manufactured today? Perhaps for racing or some very high-performance engines?

I would think such a design might be stronger than a chain-driven setup. Maybe not as fuel-efficient for a street engine? Any thoughts pn the subject?

 

[Rand]

In modern engines its much more costly and noisy to implement.. IIRC some exotics use it.

 

[OVERKILL]

The Ford Cammer (427 SOHC) had an aftermarket gear drive kit made for it:

And the Ford "Indy" Cammer was gear-drive:

 

[Gyro Gearloose]

I was reading about one mfg by VW while waiting at the tire shop about 15 years ago. They had to do something elaborate like put tensioners on the idler gears between the crankshaft and cams to account for block growth with temperature change. Otherwise the gears didn't mesh correctly and they couldn't maintain precise valve timing. After reading that article I understood why chains and belts are the norm.

 

[Passport1]

It is called the Desmodromic valve system. Ducati motorcycles have used this arrangement for years. Some F1 engines use it also. It eliminates the potential of valve floating at high rpms. Because it uses a complicated gear train it can be noisy.

 

[MRC01]

Honda's VFR750F motorcycle had gear driven cams. It was an interesting engine, a 90* V-4 with dual overhead cams. The 90* V-4 configuration has perfect primary & secondary balance is very well balanced.
The "cruiser" version of the same engine, the VF750C, was also a 90* V-4 but had chain driven cams and a 360* crankshaft. I owned one of those, a great engine.
All that said, I don't know of any practical benefits of gear driven cams. The benefits touted in marketing literature don't seem to hold up in the real world.

 

[spasm3]

I remember hearing a SBC with a pete jackson gear drive. You could hear it so far away. Straight cut gears i guess.

 

[UG_Passat]

The VW V10 TDI on the Touareg is a maintenance nightmare

 

[clinebarger]

Many heavy duty diesel engines have gear driven OHC configurations.....Detroit 60 Series, Caterpillar C15 & Cummins ISX are a few examples.

 

[tcp71]

I think some ilmore marine engines have gear driven cams.

 

[MichiganMadMan]

Honda VFR motorcycles from the mid-80's to around 2004 or so. Still nothing like hearing the shrieking straight-cut gear driven cams contrasted with the deep growl of the V4 turning 11,000 RPM to put a smile on your face.
The RC51 was also gear driven, if memory serves.
I believe it was a response to some rapid wear issues with chain driven cams on V4 engines.
I think the Cummins B-series has gear driven cams, possibly the DuraMax as well. Those are angle cut or herringbone so they aren't as loud.

 

[brages]

It is called the Desmodromic valve system. Ducati motorcycles have used this arrangement for years. Some F1 engines use it also. It eliminates the potential of valve floating at high rpms. Because it uses a complicated gear train it can be noisy.

View attachment 64020

That's a system to eliminate valve springs, not quite what the OP is asking about.

From a short research, I believe Ducati used bevel gears to drive the cams up until the 80's, when they switched to timing belts, and may have some timing chains as well. Still keeping the desmodromic system.

 

[DGXR]

I also thought there were some engines where the cam gears were driven by a shaft off the crank, rather than a series of transfer/intermediate gears.

 

[brages]

I also thought there were some engines where the cam gears were driven by a shaft off the crank, rather than a series of transfer/intermediate gears.

You mean like with bevel gears and a shaft running up to the head? Original post is talking about overhead cams.

 

[DGXR]

You mean like with bevel gears and a shaft running up to the head? Original post is talking about overhead cams.

Yes, an overhead camshaft, driven by a shaft off the crank... something like these:

I don't know of anything like this that made it into production, in an automotive application.

 

[flanso]

Yes, an overhead camshaft, driven by a shaft off the crank... something like these:
View attachment 64453View attachment 64454
I don't know of anything like this that made it into production, in an automotive application.

Porsche Type 547 four cam engine, circa 1950s

 

[Overfill]

Many heavy duty diesel engines have gear driven OHC configurations.....Detroit 60 Series, Caterpillar C15 & Cummins ISX are a few examples.

MTU Categories and FZG

Chevron lists the 400 SDE and 400 XLE as both meeting "MTU category" 2.1 and 3.1, respectively. 1. Going through the Afton Handbook, does this mean that it meets MTU MTL 5044, for multigrade "1 to 3" or "3.1"? 2. If so, there is a seemingly stringent FZG test it must meet. Does anyone know how...

bobistheoilguy.com

 

[ChristianReske]

Hondas S2000 engine has a partly gear drive. A very short cam chain drives a center gear. The gears are helical cut to reduce noise.
But, this was not good enough for Honda.

If you look cloesly at the cam shaft gears, you notice that they are assembeld of two parts, a thick and thin one. These are pre-loaded with a spring inside. (entangeld or interlocked? Wich one is the correct term?) Therefore, the gears mesh together without any play. There is no gear noise when the engine runs and the timing of the cams is very accurate.

 

[Saabist]

I don't know of anything like this that made it into production, in an automotive application.

1946-1952 Crosley 4-cylinder engines employed a shaft-driven overhead cam.

The original Crosley "COBRA" brazed sheet-metal engines used straight-cut gears. This was later changed to spiral-cut gears to cut down on noise.

 

[Imp4]

Gear driven cams.
Too many parts.
Too much noise.
Too expensive.
No practical performance or economy gain.

What's not to like?!?
For a daily driver it's a solution in search of a problem.