Dump the gear and go timing chain?

[Alky V6]

My set is so quiet that I broke out the stethoscope. Even with a stetoscope I couldn't pick out any noise that I could call as coming from the gearset. Amazingly quiet. Maybe the harmonics that people talk about with gearsets has more to do with torsional harmonics than with noise related harmonics. Crankshaft tortional harmonics transferring more easily to the valvetrain due to the more solid connection established by the geardrive. Just my thoughts on the subject.

Geardrives that whine a lot are a sign that the gear mesh clearances are too excessive and/or are not stable. Which could easily be the case with a floating idler.
In any machinists handbook that explains gear mesh clearancing, with the style of gear that you have with a camshaft geardrive, you will find that excessive noise is a symptom of excessive clearance. Too little clearance, you get gear wear and possibly other mechanical issues.

 

[norbs]

My set is so quiet that I broke out the stethoscope. Even with a stetoscope I couldn't pick out any noise that I could call as coming from the gearset. Amazingly quiet. Maybe the harmonics that people talk about with gearsets has more to do with torsional harmonics than with noise related harmonics. Crankshaft tortional harmonics transferring more easily to the valve train due to the more solid connection established by the geardrive. Just my thoughts on the subject.

Geardrives that whine a lot are a sign that the gear mesh clearances are too excessive and/or are not stable. Which could easily be the case with a floating idler.
In any machinists handbook that explains gear mesh clearancing, with the style of gear that you find with a camshaft geardrive, you will find that excessive gear mesh clearance will cause excessive noise. Too little clearance, you get gear wear and possibly other mechanical issues.

Interesting , how were you spinning it?

 

[Alky V6]

Interesting , how were you spinning it?

How was I spinning it? The engine was running on its own.

 

[norbs]

SOrry, confused which motor is this?

 

[Squid4life]

SOrry, confused which motor is this?

Norbs, I assume he is talking about the Stage I motor before he pulled it to go Stage II heads. I have talked to Donnie a little bit about how he set his up to make sure the gear mesh was spot on with good clearances, etc. Good info.

 

[HouseofSpeed]

Good topic....had this discussion many years ago with Smokey Yunick....the God of Combustion put cam drives in this order..... 1)Belt (Jesel-drive) 2) Chain and 3) Gear.

 

[turbobitt]

Good topic....had this discussion many years ago with Smokey Yunick....the God of Combustion put cam drives in this order..... 1)Belt (Jesel-drive) 2) Chain and 3) Gear.

What, this whole time I thought Tom Hoover was the God of Combustion......
Allan G.

 

[Alky V6]

"I see no reason to ever use a chain to drive the camshaft in a racing engine! In my opinion, the only sensible way to turn the cam is with a two-gear drive. Every pure racing engine I've ever seen-Offenhauser, Cosworth, or almost anything else you can name-uses some sort of gear arrangement to drive the camshaft or, in multiple-cam engines, the camshafts. In some racing engines the location of the cam(s) may require a multiple-gear arrangement, but in the typical V8, the camshaft is relatively close to the crank, and there's just nothing that is as simple and reliable as a two-gear drive."
He goes on to explain some testing he did with chains and comes to this conclusion. "I'm not about to say that a gear drive is completely bulletproof, but I'm dead certain that it is foolish to drive the camshaft in an endurance engine with chain!"

ref: Power Secrets by Smokey Yunick with Larry Schreib. ISBN 0-931472-06-7 S-A Design. Copyright 1989

This information I found in Smokey's book is part of the reason why I went with a geardrive.

 

[HouseofSpeed]

Can only tell you what the man said in person at a roundtable discussion at PRI in the late 90's....probably because of improvements in technology from when Power Secrets was published. What is interesting is that he doesn't mention belt drives there at all....but that has been the norm in Cup racing for years.

 

[geno]

[quote="Alky V6, post: 3157338, member: 2722
Copyright 1989 That was 24 years ago Donnie Im pretty sure things have changed and belt drives is a good way to go as well.

 

[Alky V6]

Can only tell you what the man said in person at a roundtable discussion at PRI in the late 90's....probably because of improvements in technology from when Power Secrets was published. What is interesting is that he doesn't mention belt drives there at all....but that has been the norm in Cup racing for years.

I just thought it would be interesting to add what Smokey thought at the time, of the drive systems that have been available from the beginning, up to 1989. His information on his studies on timing chains with strobe lights is very interesting. You should pick up a copy and read it sometime.
Something else that is very interesting. A lot of high end, purpose built endurance engines still are designed to this day with gear drives.
Is Nascar allowed to use a gear drive system? I would bet they aren't.

 

[Alky V6]

[quote="Alky V6, post: 3157338, member: 2722
Copyright 1989 That was 24 years ago Donnie Im pretty sure things have changed and belt drives is a good way to go as well.

The thing that many don't realize is that belt drive systems are prone to the same sort of whipping around as chain drives are. Just watch a supercharger belt system in slow motion, or any belt system in slow motion for that matter.

 

[HouseofSpeed]

I just thought it would be interesting to add what Smokey thought at the time of the drive systems that have been available from the beginning, up to 1989. His information on his studies on timing chains with strobe lights is very interesting. You should pick up a copy and read it sometime.
Something else that is very interesting. A lot of high end, purpose built endurance engines still are designed to this day with gear drives.
Is Nascar allowed to use a gear drive system? I would bet they aren't.

I have read it...knew the man pretty well actually. That was my point, I have assembled Cup (NASCAR) engines and they use Jesel (belt) drives...and have for a long time. If a gear drive were superior...they would be using it. I have also assembled some LS based engines for off-road endurance applications (King of the Hammers) and they use chains.....offshore powerboat engines supplied by Sterling and Mercruiser use belt drives as well. Gear drives create harmonics that are damaging to lots of components found in a competition environment.

Again I think it depends on application....

 

[HouseofSpeed]

The thing that many don't realize is that belt drive systems are prone to the same sort of whipping around as chain drives are. Just watch a supercharger belt system in slow motion, or any belt system in slow motion for that matter.

Donnie, a supercharger belt and accessory belt drives don't operate under the same tolerances as a cam drive. An S/C belt is designed around a certain amount of slippage...and the distance between the crank snout and the blower drive is far greater than the relationship between the cam and crank sprocket. If a belt drive were so prone to flailing around (and yes they do move around....as do the gears in a gear drive when observed on a Spintron) with a negative affect...they would not be found in 10k RPM race engines that are the norm for most sanctioning bodies.

Again, its all about application.....I have never been a gear drive fan based on my experience as an engine builder.

 

[Alky V6]

I have read it...knew the man pretty well actually. That was my point, I have assembled Cup (NASCAR) engines and they use Jesel (belt) drives...and have for a long time. If a gear drive were superior...they would be using it. I have also assembled some LS based engines for off-road endurance applications (King of the Hammers) and they use chains.....offshore powerboat engines supplied by Sterling and Mercruiser use belt drives as well. Gear drives create harmonics that are damaging to lots of components found in a competition environment.

Again I think it depends on application....

I really don't have anything against a belt drive, except that any whipping around of a component is going to cause fluctuations in cam timing and anything else being driven off of the cam sprocket.
Since this thread is primary about comparing a chain drive to a gear drive, I have a few questions.
Do you know if a gear drive would be legal to use in NASCAR?
When the BUICK V6 was used in NASCAR during the 80s, did they use chains or gear drives?
Weren't BUICK V6s built for Indy Lights duty supplied with a gear drive? Why didn't they use chains?
Can you more clearly explain the type of harmonics that goes on with a cam gear drive? What valvetrain components get affected by it?

 

[Alky V6]

Donnie, a supercharger belt and accessory belt drives don't operate under the same tolerances as a cam drive. An S/C belt is designed around a certain amount of slippage...and the distance between the crank snout and the blower drive is far greater than the relationship between the cam and crank sprocket. If a belt drive were so prone to flailing around (and yes they do move around....as do the gears in a gear drive when observed on a Spintron) with a negative affect...they would not be found in 10k RPM race engines that are the norm for most sanctioning bodies.

Again, its all about application.....I have never been a gear drive fan based on my experience as an engine builder.

Actually, I was thinking of a cogged supercharger belt drive. Like what is normally found on a Top Fuel car. Not the type that would allow any slippage.
Distance between sprockets doesn't make a whole bunch of difference. If that were the case, then an idler pulley on a cam belt drive would be unnecessary. Additions of idler pulleys to belt drive systems that used to be run without an idler pulley seems to be the new thing lately. The idler pulley is obviously there to help control and stabilize the belt. So you see, belt systems are not perfect either.

Since you did know Smokey better than most of us, I'm sure, maybe you can explain why the 180 degree change on his opinion on chain drives versus gear drives. When you read his book, he obviously had a very bad opinion on chain drives. And that was for a V8. I'm sure his opinion was worse when you factor in the fluctuations associated with a V6, particularly if high spring pressures are being used. Much of that explained very well by Jim Ruggles.

 

[Alky V6]

[quote="Alky V6, post: 3157338, member: 2722
Copyright 1989 That was 24 years ago Donnie Im pretty sure things have changed and belt drives is a good way to go as well.

That's easy to say, but have things really changed? If so, how have they changed? It sure seems to me that people are still managing to break chains with relative ease. And I don't think aligning sprockets is a revolutionary idea.

 

[Cheeseburger]

That's easy to say, but have things really changed? If so, how have they changed? It sure seems to me that people are still managing to break chains with relative ease. And I don't think aligning sprockets is a revolutionary idea.

Are the ones who broke chains using aluminium blocks or iron blocks?

 

[HouseofSpeed]

I really don't have anything against a belt drive, except that any whipping around of a component is going to cause fluctuations in cam timing and anything else being driven off of the cam sprocket.
Since this thread is primary about comparing a chain drive to a gear drive, I have a few questions.
Do you know if a gear drive would be legal to use in NASCAR?
When the BUICK V6 was used in NASCAR during the 80s, did they use chains or gear drives?
Weren't BUICK V6s built for Indy Lights duty supplied with a gear drive? Why didn't they use chains?
Can you more clearly explain the type of harmonics that goes on with a cam gear drive? What valvetrain components get affected by it?

There is no rule against a gear drive....but no one uses them. Little known fact, Ford's FR9 Cup engine places the damper / balancer behind the timing belt to further isolate crankshaft vibration / harmonics from the timing components. In fact, about the only "class" I can think of that runs gear drives much are sprint cars....but even there, some builders run chains...and not belts. I am attaching a photo of a front cover that is supplied by Roush-Yates for the pre FR9 engines which shows how they eliminate chain bounce....

All of the Busch motors that I have seen in original form...some still marked with lash settings on the valve covers....were equipped with chains. Typically the open wheel stuff will lean toward gear drives because of RPM and the fact that often the drives are exposed and utilized as part of the accessory drive system for other pumps and such. Chains can see the same duty though, because the cover that I am showing you here has a very heavy duty chain setup behind it that is responsible for also carrying a 5 stage oil pump, vacuum pump and the power steering pump.

Not just valvetrain components that are affected...but rather the "stacking" of harmonics throughout the engine that will rob power and cut down on longevity of components. Any vibration...at any frequency...that can be reduced or eliminated produces power.

 

[Cheeseburger]

There is no rule against a gear drive....but no one uses them. Little known fact, Ford's FR9 Cup engine places the damper / balancer behind the timing belt to further isolate crankshaft vibration / harmonics from the timing components. In fact, about the only "class" I can think of that runs gear drives much are sprint cars....but even there, some builders run chains...and not belts. I am attaching a photo of a front cover that is supplied by Roush-Yates for the pre FR9 engines which shows how they eliminate chain bounce....

All of the Busch motors that I have seen in original form...some still marked with lash settings on the valve covers....were equipped with chains. Typically the open wheel stuff will lean toward gear drives because of RPM and the fact that often the drives are exposed and utilized as part of the accessory drive system for other pumps and such. Chains can see the same duty though, because the cover that I am showing you here has a very heavy duty chain setup behind it that is responsible for also carrying a 5 stage oil pump, vacuum pump and the power steering pump.

Not just valvetrain components that are affected...but rather the "stacking" of harmonics throughout the engine that will rob power and cut down on longevity of components. Any vibration...at any frequency...that can be reduced or eliminated produces power.

View attachment 181996

Interesting tensioner setup...