Join Date: Apr 2000
Location: Whittier, California
Of no consequence...Oh, really?? Well, thinik about this, EVERY Pro-Stock engine used today is running either a Jesel belt drive or a common duoble row timing chain set, every one. What the actual real racers found is that the gear drives actually had too much harmonic distortion transfer from the crank to cam and valve train.
Now, Pro-Stockers run cams with between .900 and 1.100 valve lifts through the rocker arm ratio, and $1,700.00 a set titanium valve springs they change in 15 runs. When these same valve trains were run with a non-daqmping timing system, the valve springs lived 7 tp 8 runs. Since a Pro-Stocker is normally aspirated (PULLS mixture into the cylinders), harmonics is a very important issue, as it disturbs the intake flow and carburetion/jetting.
Dual idler gear backlash is seen as the engine is on steady rpm output, and at deceleration, and allows the cam and valve train to chatter and have erratic operation, even in acceleration mode. This ain't good for notin' in the valve train, and is vitally consequential.
As the dual idler jobs get loser, the amount of harmonics and vibration gets more intense, with growing adverse effect. Eventually, the idler gears get so loose the contact of the teeth get twords the limit of strength, and the teeth begin to chip and will fail shortly after this.
There were lots of roundy-round racers in Merced, where I had a speed shop, and they drive of choice was the Junkson dual idler nightmare. The cars that consistantly won came from my oir another shop, and always had chains on them, the ones that always had cam, rocker, spring, valve train problems used the dual idler junk. Once the racer saw the light and went chain, he began to get a season on a chain and sprocket set and began to not have the valvetrain problems and could actually tune the engine, something that wasn't possible with the gear drives.
Blower alchohol and nitro engines run gear drives, but they only use cams with lifts through the rockers at or very near the .700 levels, and, since they vibrate the daylights out of themselves, not much damage is done from them as far as harmonics. Since the mixture is pressurized into the cylinders, the harmonics become moot in those supercharged powerplants.
Of no consequence-for a normally aspirated engine?? Makes every consequence, bet your life it does. Ask any real and knowledgeable cam or carb person about distortion and the prblems it causes in the valve train and/or intake tract, you'll hear the same thing, vitally important not to have any. You won't hear any of the real truth in the big-time hype ads for this junk dual idler garbage.