new 2/15/03
I found this photo of the DOHC of a 1989 Corolla 4A-F engine with 229,487 miles at http://www.bobistheoilguy.com . The engine lived on Mobil 1 oil.
Other than the engine is clean and lasted a lot longer than an unwelded V8SHO engine, the use of gears requires more room, weighs more and if you think about it the driven cam would have to be reverse rotation.
Straight cut gears are noisy, bevel gears like above create end loads and all gears must have backlash. Without changing the direction of rotation they only way to replace a pair of sprockets with gears is to introduce a idler gear. I like the sprocket solution better if not mounted with spit and prayer.
In this case the cams are not hollow, nothing is pressed on. I thought folks might like to see one example of how Toyota does DOHC engines.
Comments? Send them here.
Buford