DragStuff

Hi new to site. Would like some input on gear drives for mark 5 bbc witch will be used on street rod with solid roller cam?

Hey, welcome the site.

Gear drives cause harmonic vibrations that are not good for your motor. I don't like them. Chains are cheaper any way.
Just my 2 cents

supernova wrote:Hey, welcome the site.

Gear drives cause harmonic vibrations that are not good for your motor. I don't like them. Chains are cheaper any way.
Just my 2 cents

Thanks fore your answer. got a 57 chev from ft.worth last year.

I've been running a Pete Jackson gear drive on my BBC blower build for quite awhile and I'm about to swap it out for a Cloyes double roller timing set.

I'm swapping back to the double roller to get the horsepower back and to get rid of the vibration from the gear drive. I found opinions varying on whether gear drives are problematic or not, <shrug>...

Like a lot of things, your mileage may vary.

For a street car I would go with a chain and good one because of your cam.

The dual idler gear drives are only good for one thing, making noise.

The single (fixed) idler gear drives are another story, very strong and very accurate valve timing, the only way to make harmonics with them is to set them up wrong.
They are also pretty cashy, $800-$1500 for one and worth every penny, we've had one on our drag motor for 5 years, still looks new and I'm not exactly nice to it.

There is a reason every top fuel car in the country runs those gear drives.

Just a little rant I had to do.
Larry

3 gear versions are the way to go. Never a problem. I have a 20 year old Donovan and a 25 yr old Milodon that I still use. You just can't kill them unless you run some chunks through them but at that point you are done anyway.

I await the day when some independent testing lab can show me A-B-A datalogged, scienced proof of this vibration and HP loss w gear drives. It has always sounded like spin created by chain or rubber band manufacturers. I feel the stretch, flop and timing retard with the rubber bands and chains is a far worse trade off.

Besides, IF there was a HP loss from gears it seems like a great trade off since even today's mild engine builds make a ton more HP than they did 10 years ago. Most guys have more HP than they know what to do with these days. AND most of us can't tune close enough to tell the difference.