Thread: Gear Drive, Gear Misalignment

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This question pertains to a gear drive on a BBC but I suppose we could be talking about any engine.

Question is, when the cam and crank sprockets are installed, how much misalignment (if any) is acceptable between the two, once the idler gears are installed? Anyone else seen this? Any ideas on what "acceptable" is? The directions state that they may not align perfectly but doesnt get specific.

And if this type of problem is encountered, what can cause it and how does one go aobut fixing it? (I believe, possibly, that the crank sprocket sticks out further from the front of the block than does the cam sprocket)


Thank you for the knowledge for which you are about to share.

If I remember correctly, to maintain alignment you will need a Torrington bearing behind the cam sprocket, and a button on the front of it.... With all the good timing chain sets out nowadays, I haven't had to run one of the gear drives for better then 20 years... IMO they do more harm then good anyway.....

Originally Posted by 65cayne

This question pertains to a gear drive on a BBC but I suppose we could be talking about any engine.

Question is, when the cam and crank sprockets are installed, how much misalignment (if any) is acceptable between the two, once the idler gears are installed? Anyone else seen this? Any ideas on what "acceptable" is? The directions state that they may not align perfectly but doesnt get specific.

And if this type of problem is encountered, what can cause it and how does one go about fixing it? (I believe, possibly, that the crank sprocket sticks out further from the front of the block than does the cam sprocket)


Thank you for the knowledge for which you are about to share.

you bolt the cam gear to the cam, and drive the crank gear as far as it will go then the chain should make it run true. some motors have cam retainers, some use buttons and some don't use anything except the cam and chain.

Originally Posted by lt1s10

you bolt the cam gear to the cam, and drive the crank gear as far as it will go then the chain should make it run true..

Just to clarify, I have a gear drive, not a chain drive (sorry for the mis-communo). When you say "drive it as far as it will go", what if that is not far enough? Ever encounter that type of problem?
I would assume that, like a chain driven gear set, the gears should align very close, if not perfect, no?

There is a torrington bearing installed (washer-like bearing?) but it does not bring it (the cam sprocket) out far enough.

Originally Posted by 65cayne

Just to clarify, I have a gear drive, not a chain drive (sorry for the mis-communo). When you say "drive it as far as it will go", what if that is not far enough? Ever encounter that type of problem?
I would assume that, like a chain driven gear set, the gears should align very close, if not perfect, no?

There is a torrington bearing installed (washer-like bearing?) but it does not bring it (the cam sprocket) out far enough.

sorry about that. won't thinking gear drive. this is what i found. http://www.edelbrock.com/automotive/timinggear.html

that's okay, I appreciate the info though.

Geez, I know that a lot of folks dont like the gear drives, but I was hoping more people would fess up to using (or, having used) them and offer their perspective

I am just searching for opinions. I am sure that the "mature" hotrodding croud here at CHR would think no less of someone for admitting that they have a gear drive.

Hopefully some more will chime in...

Originally Posted by 65cayne

that's okay, I appreciate the info though.

Geez, I know that a lot of folks dont like the gear drives, but I was hoping more people would fess up to using (or, having used) them and offer their perspective

I am just searching for opinions. I am sure that the "mature" hotrodding croud here at CHR would think no less of someone for admitting that they have a gear drive.

Hopefully some more will chime in...

How old do you have to be to be considered "mature"?
I suppose if I have to ask that means I am not.
In the summer of 86 I had a BBC in a Camaro nothing really that quick in fact I think the best e.t. it had in the 1/8 mile was a 7.06 if I remember correctly.
Dad finally got me to quite the old exhaust down then he was up-set about the sound of the old Summers Brothers gear drive.
He sat me down and talked to me about harmonics and vibration from the valve train going straight to the crank and not to be mad if I had some strange looking patterns on the bearings.
He said even though the timing chains stretch and cause bad cam timing they where like giant rubber bands and would help my bearings to live longer.
I did'nt listen but I keep running them and by the summer of 87 I had some bearing issues in the old BBC.
Guess what old dad was right.
He still can't believe that a 383 I built for his 65 Chevy makes over 500 hp at the crank runs on pump gas and does not require any valve train adustments.L.O.L.

i have had guys come in the shop and want me to build a big block . i say ok then they walk in with a Gear Drive .i have told more than one guy that i will not build them ANY THING with one in it . thats all i will say on this. erik. dave and me have posted on why not to use one. i sure there are more that just us that do not like them . when some wants to add harmonics to any engine (gear drive) is not really building the best engine that they can.but they are hot seller on e-bay

Geez, I know that a lot of folks dont like the gear drives, but I was hoping more people would fess up to using (or, having used) them and offer their perspective

Dave did just that, and so did Pat. I've used them too, and they suck. You're essentially asking folks how to fix something they wouldn't use themselves, so if they're probably going to toss in their opinion free of charge.

I don't think any less of you because you want a gear drive, but then all I'll tell anyone on this board is what I think . . . not what they want to hear.

GEAR DRIVES ARE FREAKIN COOL!!!!!! For about a month.

Ok,
I have a gear drive. I have had this engine since the early 90's, gear drives were a little more popular back then. I then read about the gear drives adn all of the harmonics they put back in the cam and crank. My next venture will be an external belt drive, one day.

Okay people....I had a feeling this would happen. I am well aware of how many of you feel aobut using gear drives. What I am asking, is NOT HOW YOU FEEL ABOUT USING them. What I am asking for is your opinion, as mechanics, as machinists, gear heads, motor heads, axle greasers, etc...on the nature of my gear misalignment. What could cause it ? how much is too much? how to fix it?

You all may think that the gears in my head are misaligned and that is just fine.. I just want your technical expertise because a lot of you know a heck of a lot more than I do and have probably seen more gear drives than I have (in real life, on an engine). I gave you all (the CHR croud) a "mature" label. My wife says that when I hammer the throttle in our car that I am not being "mature". If that defines mature, then well... am pretty sure you all are "not mature" right along with me. Fact is, when it comes to technical issues, you guys are all business (i.e. very mature) which is what I was talking about and I like that. I know, I know, how much gear drives suck and all that, but I have one and I am not changing it in the near future.

So thanks to all of you folks for chiming in. Can some one talk to me some more about the misaligned gears?

if you shim it out more you maybe be asking for troulble. you need to know if the gears machine right .there should be two washer for the torrington or may be caged with the torrington trap in side the washers or some use one brass washer to. was the block you have been machine in front for a washer on the block? this is the face were the cam top gear rides wore in ? if the cam is back to far in or out there a good chance the lifters may not turn .try a old timing set and see were you are if that looks good then you will know that you have to do you may shim it. alot of the older block will eat the cam so if you did do have any cams go out before then i would try not to move it . with the gears you could be in or out as long as they do not run off the whit of the face of the gear

Is it 1/16" out of alingment ,1/8",1/4"?

Well I didnt read all the way down so sorry for replying if your question was already answered lol.
When I put a gear drive on my SBC 350 it called for a bearing behind the gear on the cam shaft, and a button on the front. The bearing was "rounded" to a degree (0, 2, 4, 6, 8) they came in a color coded set with my gear drive.
I -believe- the degree of the cam bearing was direct with what degree before TDC you wanted the engine to run. I used 0 degrees. in a stock setup.
Then the cam gear bolted on, and when you install the timing cover a button goes right in the center and has to have a tiny amount of back pressure againt the timing cover (to much will eat a hole threw the cover)

Installing the idler gear, I can't remember which way the dog bone faces but the idler gear should have freeplay on one side and not the other. When I installed mine I but the Harmonic Damper on the end of the crank with some bolts in it so I could turn the crank slightly, allowing the idler gear to slide into place with the light tap of a hammer.

:P if you got the loud cut gear its REALLY loud for about 2k miles, after that it quiets down a bit.. but its still loud enough to wear my friends can her me coming down the street quite a ways.