View Full Version : Gear drive vs. roller cam

02-19-2005, 12:50 PM
Has anyone heard or run into any issues with using a roller cam setup and a gear drive. Every roller cam kit I see uses a roller timing chain and even the tech guy at Comp yesterday told me to use a roller-chain and when I asked why, he literally couldn't give me an answer. Anyone here have any experiences or can explain this? Thanks guys!

02-19-2005, 07:00 PM
I dont care for gear drives on anything really but after talking with some engine builders eons ago the reasons they stated were mainly due to the harmonics that get transfered to the valve train which is already getting beat up pretty hard as it is.

Ive personally witnessed issues with gear drives setting off the knock sensor on fuel injected vehicles and Ive actually taken two of them off of locals TBI chevy trucks that were causing the knock sensor to come unhinged killing power due to the retarded timing.

More than likely you will tire of the noise after a while as well as tire of ppl asking "whats wrong with your car its making a funny noise?".

My .02

02-19-2005, 08:09 PM
I haven heard too much good inpunt about gear drives, from what I understand alota people install them to get that annoying whine. I personally like the Jesel, and comp cams belt drive, I little pricey tho. I think there are a few other belt drives but not to my knowlege. Mycyclone made a good point about the harmonics. Its bad enough with a regular timing chain.


02-19-2005, 08:21 PM
What's up Keith? I have heard the same thing about the harmonics being transfered to the valvetrain. I think the main appeal of the gear drives (for most people) is the sound. They are also supposed to be more accurate than a chain because it can't stretch like a chain. Now, we have belt drives that provide the same accurate timing without the harmonics. If on a budget, I'd go with a high quality double-roller like the one from comp cams. Just my 2 cents. See ya,

02-19-2005, 09:21 PM
Personally I ran a Pete Jackson "noisy" gear drive in a brand new motor and it had less than 5 miles on it when I pulled it out. I pulled it because I could'nt hear anything the motor was doing and it made it a lot harder to tune or tell if anything was wrong. It's up to you but I just thought I'd point out the noise issue.

02-19-2005, 10:23 PM
Gear drives are junk!

02-19-2005, 10:24 PM
BTW, belt drives are THE way to go but there are two hurdles to get across.. One is belt drives are pricey and the other being that no one that Im aware of makes a belt drive to fit a factory GM style roller cam front snout. Comp cams is willing to grind an old style flat tappet snout on a roller cam but its an added cost so you will end up with very close to a grand in just your cam and the mechanism to turn it.

No thanks...I'll stick with a good ol double roller chain and spend the money eslewhere that produces more hp/dollar.

02-20-2005, 03:38 PM
Well, I know of several reputable manufactures that make a good gear drive unit that's not as noisy as others and I've even run a few on hydraulic flat-tappet cars without issue but my main reason for wanting it is my brother broke his nice double-roller Clyoles (sp?) unit and it destroyed the entire motor. Also, the Chevelle is very subtle and sinister like alot of you pointed out and I thought the whine might suit the agressive personality I'm creating for the car. However, I'm not willing to do it at the expense of my entire engine and I trust you guys so I'll throw that idea out the window and work more on fine tuning the exhaust note. Also, the cars getting insulated like a spacecraft so the noise from the inside isn't an issue and i was planning on dyno tuning the engine with the EFI setup out of the car but you all bring up valid points. I like the belt drive idea but have very little experience with them so my reservations might be due to being uninformed.
Once we do intial testing to ensure the car meets all of it's performance goals, we're putting her on the down low until it's official debut at it's booth at SEMA this year and then the car will be driven.....alot. Occasional track events, lots of shows, Power-Tour, lots of road miles...is a belt drive okay for that type of driving?

02-20-2005, 04:12 PM
The car will get a lot of street miles huhÖ As much as I like belt drives the only thing that concerns me with using one on a car that sees a lot of street miles is road debris when using a dry belt. For a weekend warrior I wouldnt think twice about it but in a situation where you may be far from home even a piece of gravel kicked up into the dry belt drive system could spell big trouble since they are exposed. A wet belt system is protected but doesnt give that "ooh ahhh" factor that John Q Gearhead has come to expect since he cant see it.

BTW, I cant remember the last time I or anyone I know broke a double roller from anything other than a catastrophic engine failure which the chain didnít cause but was a victim of. The do wear out but breaking one is pretty rare so any ideas what caused yours to break?

Steve Chryssos
02-20-2005, 05:26 PM
Timing chains need to be blueprinted like every other part in a quality engine build. If a timing chain snapped it was more than likey too "tight" Overlooking chain tension is a common mistake. If checked, a timming chain should last just fine. If you want the best, get a belt drive. Most new cars have belt drives (Hell, a 78 Chevette had a belt drive. You can buy a cover for a belt drive if debris is a concern.
Gear drives have no place in a modern high performance engine.

02-21-2005, 01:55 AM
We're not sure what the cause was but two links let go nice and clean..the engine was used so it wasn't our mistake this time. I suspect Steve is probably right on head. Is there any concern with the belt losing elasticity over time or causing erratic timing from expanding and contracting in a performance application? we just changed some of the engine plans and we now expect closer to 600HP at the fly...if it's safe and you say so it's a done deal. I'll do a wet system with a cover. Never been a huge fan of Johnny Q :)

02-21-2005, 11:42 AM
I'm running a gear drive and roller cam...Haven't had any issues I can think of. If you run a quality harmonic balancer there shouldn't be any troubles... I'm running the Pete Jackson quiet gear drive, it's noisey enough.

02-21-2005, 12:05 PM
Hmmm........I'm having trouble finding a belt drive setup for less than.....$720 BUCKS!! I'm spending big money on this car but even that's hard to swallow. That's the Jesel unit and the comp cams one is 1129 for big block. So, who can get one for less? :)