Thread: Gear Drive, Gear Misalignment

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when the cylinder fires theres a big vibration (bang) times 8 at 6000-7000 rpm.That vibration has a SOLID link to the valvetrain and entire engine.A timing chain will absorb alot of it (not a solid link) from going straight to the valve train.You also have the vibrations caused by the straight gears explained above on top of that.

I wanted a gear drive myself ,but after researching its just not worth it.

Isn't the harmonic balancer there to absorb the harmonics? Or it doesn't do a good enough job? Has anyone actually done any tests, other than the belt drive companies that want to sell you a 900 dollar product, to prove that the harmonics actually reach the valves or the springs?
I have run one in the past and seen no problems what so ever. Big diesel engines run them and their vibrations from a cylinder firing are way more than what any big chevy makes.

Originally Posted by Dave Severson

Main reason there aren't as many problems on the distributor gear is that these gears are beveled gears, not straight cut gears..

As for proof of the damage caused by gear drives.... We used to run the Pete Jackson gear drives before the good double roller chain sets came out in our racing engines.... Had a lot of problems with valve trains, and strange wear on cam bearings and other valve train parts. We switched to the Cloyes double rollers when the came out, no more valve train or cam bearing troubles... Is this proof? Probably not. Just an observation.

Basic engineering will show that the chain will abosorb some of the vibrations, straight cut gears do not. If anything they amplify them.... The gear drives do not make timing more accurate then a high quality chain. All they really do is make noise.... To some I'm sure this noise is kewl.... To me the noise is just going to drown out any small ticks, clicks, or whatever's that I will never hear over the gear drive....

Sometime, on a car with a gear drive, when it's running put your fingertips on the timing chain cover.... You will feel some very strong vibrations... These vibrations (harmonics) will do nothing to improve performance in an engine...

I read somewhere that due to the excessive harmonics with a gear drive, 4-6* of cam timing variation is common, which I wouldn't think is a good thing

well a big block runs more rpms then a diesel and more lift i do not think they run strait cut teeth gears or a pete jackson gear drive . i have seen the proof . i can not show you. just tell you what i have seen you want proof well run a 760+ lift cam with one and run it to 7500 and see what will happen in time ? i have seen the best built engines and not one i have seen has one .the damper helps with the harmonics and now you are adding harmonics thru the gears from the crank to the cam? by steel gears you are adding hamonics with a chain or belt you will not have some or none with the belt. do you know the frequency of harmonics that need to be dammpen? by adding you gear drive and at what rpm? i do not know but now you have added more

I think common sense should be enough proof,but thats just me.Gear drive ,solid link,chain or belt no solid link. No harm in questioning though,thats a good thing.

You're right, big truck!!! Diesels also run bevel cut gears like some of the old six cylinders that had gears and no chain. I guess if you won't accept any of this as proof, just go run one and find out. Just the very sound of a gear drive should tell you that something isn't right!!!! A lot of us have allready learned that from first hand experience.

I don't think that the sound is saying something is wrong. Straight cut gears in transmissions make noise also. I have run one and have since sold the engine. It's still going strong with over 20,000 miles on it. Nothing really radical though. Just a 350 with a Comp 280 Magnum cam, ported heads, etc. You might see something at the lift and RPM Pat quoted but I wish somebody would do a test on this and put it to rest. It would be interesting to flog an engine on the dyno swapping timing devices and checking vibration levels, horspower, torque, etc. Maybe I should send a letter to one of the magazines and see if they are game.

Originally Posted by mrbigg

I don't think that the sound is saying something is wrong. Straight cut gears in transmissions make noise also. I have run one and have since sold the engine. It's still going strong with over 20,000 miles on it. Nothing really radical though. Just a 350 with a Comp 280 Magnum cam, ported heads, etc. You might see something at the lift and RPM Pat quoted but I wish somebody would do a test on this and put it to rest. It would be interesting to flog an engine on the dyno swapping timing devices and checking vibration levels, horspower, torque, etc. Maybe I should send a letter to one of the magazines and see if they are game.

Here is one for you to read.
Go to Edelbrocks web site.
The gear drive is made by Cloyes for Edelbrock.
Click under valvetrain.
Then click under "Gear drives"
The note basicly says not for use above 7,000 rpm's or on a computer controlled vehicle with a knock sensor.
I think I am done "beating a dead horse" now.

I did a search and found a Camaro forum. One of the posts said that John Lingenfelter and others could not prove the theory of gear drives causing harmonics. I know that guy has built tons of engines and would like to hear his opinion. Did he ever recover from that bad accident he was in a while back?

You're not going to hear his opinion. He died on Christmas Day, 2003.

Originally Posted by mrbigg

I don't think that the sound is saying something is wrong. Straight cut gears in transmissions make noise also. I have run one and have since sold the engine. It's still going strong with over 20,000 miles on it. Nothing really radical though. Just a 350 with a Comp 280 Magnum cam, ported heads, etc. You might see something at the lift and RPM Pat quoted but I wish somebody would do a test on this and put it to rest.

We did.... We ran them in the late 60's and well into the mid 70's until the good double roller chain and gear sets came out... We constantly had valve train and bearing problems, including the cam bearings!!!! Harmonics are bad in any engine... As for straight cut tranny gears, yes they do wear faster then bevel cut gears.. Take one of the old Doug Nash full Comp trannies and run them on the street, they go bad in 10,000 miles or so. Harmonics is an engineering term for vibration. Vibration is not good in any engine, let alone one that you have spent a ton of money on to get properly balanced, clearanced, and assembled. As for flogging one on a dyno, why bother??? I had all the proof I needed 30 years ago. To me, the resurgence of gear drives is just another case of everything old is new again.... The whole gear drive issue was put to rest many years ago, only to be reborn by those who think the whine is kewl. Heck, put in a quick change with the straight cut spur gears and you'll have whine in stereo!!!! Yeah, I've had them on the street, too!!!!

We had Mobil 1 for a sponsor on our sprint cars many years ago when Mobil 1 synthetic was first introduced. Part of the sponsorship was of course to run their oil, but one of the added goodies was the spectromatic (sp?) oil examination.... When the gear drives went, the metal particle count in the oil went down. After switching to chain and gears, we raced 4 more years with no further bearing failures.... Was it the synthetic oil or the chain and gears vs. dinosaur oil and the gear drive??? Don't know..... But, I still run Mobil 1 and I still run a chain and gears. When something is good, and I've seen the benefits with my own eyes (and bank account) that's all the proof I need.

If you would like to build two identical engines, one with gear drive and one with a chain and gears I would be glad to set you up with the dyno time necessary to see the proof.... Not meaning to get on your case, just tired of the same old arguments and someone thinking those of us who have "been there, done that" should have to prove anything to anyone!!!! Sorry... I'm just grouchy today....

hey dave he loves his gear drives .i done with this bull $hit that what it is. i will say this i build a damn great engine and built many so . i would not put a geat drive on any engine . maybe he builds better engines then me so you can run them .

Are we still beating that "dead horse"? L.O.L.
Now where did I lay my club??

Yeah, but I swear this is the last time!!!!! Kind of like beating your head against the wall, it really feels good when you quit!!!!!

So . . . can I put a dual quad tunnel ram on my 305? I think it looks cool, and will it help me get a rough idle?