WoodyJ

I just fired up my 289 in my 67 fastback. When I purchased the car, it had a very sick 351, so I purchased a late production 67 289 from a friend. He had rebuilt the motor and ran it about 2000 miles one summer and than decided to rebuild a bigblock for his 68 mustang.
The motor seems to run great with one exception. When he had the motor built he decided to run a noisy gear drive. I have no idea what brand of gear drive was used. I heard his car the summer before and thought the whine of the gear drive sounded kinda cool.

THE PROBLEM is that at idle, the gear drive sounds like like a chattery diesel engine. As soon as I get the RPM's up just a little (800 -900 RMP) the chatter stops and all you hear is the whine of the gear drive.
I've taken the belts off and started the car, it's not the bearing in the alt or the water pump etc. I have also taken a long handle screw drive and listened to through the oil pan, valve covers...etc. I sware the sound is coming from the gear drive in the front of the motor.

I'm guessing there is to much or not enough play for the gear drive "dog bone" and it's hitting the timing cover or something.
It really stinks that I have to pull apart the front of this motor now that everything is installed and looking like new, but I think putting on a timing chain is the right thing to do.
Has anyone else every experienced this? Do you think what I'm thinking is correct?
Thanks!

Gun Jam

I run the pete jackson noisy gear drive and it has a slight chatter at idle as well its not really something you can hear at idle unless you listen for it. It makes a nice whine above 1500 rpm.

I think you are right about the dog bone. The drip rail inside the timing cover or the timing cover its self maybe interfering with the dog bone.

Removing the timing cover and placing a thin layer of clay on the end of the dog bone and then temporally reinstalling the cover thus compressing the clay and finally measuring the thickness of the compressed clay is a method used to determine proper timing cover clearance....something like .003 to .010 clearance is normal.... I think


-Gun

ThetaTau87

The easiest thing to do is remove the gear drive and replace it with a standard timing chain. You need to open it up to determine what the problem is anyway and good timing chain sets are not very expensive. The noise you're describing sound fairly normal for a gear drive. At idle there will tend to be some chatter with the gear teeth.

Iskwezm

there is no problem, The idler gears are a "floating" design. the rotational force keep pressure on them to reduce the "chattering, which is why it gets quieter. Mine is the same, but its not a issue or defect.Ive had mine for about 17 years now, so im pretty if it was self destructing, it wouldve happened.

Gun Jam

mine is just barley audible if you open the hood and stick your head in there at idle. If its louder than everything else at idle I would tend to think its binding on the timing cover. I guess it could be fine and some makes of timing gears maybe subject to louder chatter at idle...

WoodyJ

Thanks for all the feedback. I don't mind the whine, but the chatter at idle is fairly loud (at least in the garage with the hood off). It just sounds like something isn't right. Again, hate to start pulling a part the motor now that it's in the car, but I've decide just to install a timing chain.

craig71springsport

Glad you posted this Woody, I'm going with a gear drive on my 408w build for sure. From what I've read, the gear do open up horsepower. I think what you're hearing is just the gears doing what they're designed to do. The reason why you hear it more at idle probably because since they're not moving at higher rpm, there's more lag in between contact and the larger gap in time in between makes it sound like chatter. Kind of like a big cam, sounds like the car is about to die at idle but when you rev it, it sounds like a monster.