Timing Gear Drive

[POS Dakota]

What he said...I agree.

Not for nothing and not to invalidate this all-too-often repeated statement...where are the examples of these elusive "harmonics" that we constantly hear about but never see examples of? Where it the proof?

Does anyone have any evidence to support it?
And again, not like I am concerned with it in my application because I do not have any piston-to-valve issues and I am not turning 7000 rpm.

As far as I'm concerned, if there are no examples, let's not hear this anymore. You guys can enjoy your chains, and we'll enjoy our geardrives.
Fair enough?

Masturbating is supposed to make you go blind. I guess this means everyone on this board has taken an oath of abstinence.

In short, you cant believe everythng you hear.

A far better argument would be something like how flat tappet cams have a high failure rate (for a multitude of reasons) where roller cams don't. That would be because there is sufficient enough evidence to back the claim that I can search and read here.

I see no evidence to support the whole geardrive claim.
I do however see that the people on here using both the milodon and the cat geardrive like them and find them to be pretty good stuff.

 

[Badart]

Sorry it took a while to see this POS Dakota. I have been really busy getting this Fury together. I don't recall if my crank sprocket was misaligned like yours or not. I would not be afraid to run it. My car now has 3,000 miles on it with no issues. 0 change in sound, 0 metal in pan and oil pressure has not changed.

There have been builds on this site that have spun bearings and wiped cams with timing chains with less miles. LOL

 

[ne57]

I have to agree POS Dakota. For most its a hobby so do what makes you happy(as long as its safe!). Not that tech input isn't appreciated or valueable. If everyone were to adhere to conventional wisdom we'd all be driving much the same vehicles and all dragsters would still be slingshots. I think at its base, hot rodding is about identity. Maybe that sounds artsy fartsy but why else would we aggravate ourselves with tinkering when we could just BUY a fast car? Just to go fast? Eh, I think its more than that. Its about the doing. I know I get grief about anputting 'old hemi' in a sixties car, it doesn't 'look right'.

Hot rods are the quintessentially American folk art.

 

[RustyRatRod]

Absolutely no need for the rude potty mouth references. Everyone here seemed to be engaged in a really interesting conversation. I spoke what I know to be true......that is that the majority of serious racers do not run gear drives. I also gave the reasons. I could provide proof, but it wouldn't make any difference. You'd simply say it was not the fault of the gear drive. Hay, it's your money and your ride. Build it the way you want and have fun. But there's absolutely no need to get insulting and crude. I thought we were pretty much above that. All I did was offer an opinion based on experience of what I've seen. I offered that in good faith and with good intentions to provide another viewpoint. Simple as that. I didn't slam anyone for choosing to run a gear drive. I was civil in what I said. I expect the same in return.

 

[rickstershemi]

OK....I'm confused (not uncommon) this topic on "Harmonics" is it in reference to "Gear Drives" or "Masturbation"....?????

Rickster

 

[POS Dakota]

OK....I'm confused (not uncommon) this topic on "Harmonics" is it in reference to "Gear Drives" or "Masturbation"....?????

Rickster

haha! um both!

Rick, I attribute my longevity to amsoil!:cheers:
I've watched your car thread on moparts and I love what you're doing.
Welcome!

Seriously though guys...I mean no disrespect to anyone. I'm just kidding.
But fundamentally I hear a lot of things that it turns out simply just dont hold any water.

Same goes for cast cranks. I have heard for years how horrible they are, yet Brian H is building some damned good cast crank engines and putting people in the 10s, Not for a weekend either...with reliability!

The same can be said for anything. Elmiminate all of the variables that can cause something to fail that ordinarily wouldnt and you come to find that a lot fo things arent anywhere near as bad as people make them out to be through the rumor mill.

I am still waiting to see some evidence of how bad a geardrive is, and while I am waiting for that, all I am seeing and hearing is how good they are.:read2:

On my last motor I used a mopar timing chain which was supposed to be good. Well when I pulled it apart, it was hanging off the lower sprocket like a raw egg on a nail. It was all stretched out, I'm willing to bet if for some reason I turned the motor backwards it would have skipped teeth and gave me a really bad day...before the oil pressure issue would have. LOL

Let's get some more time with these things and see how bad they are. Thi way we have solid data if something is good or bad as opposed to pseudo-scientific speculation. I understand the theory trying be conveyed, but in practice I'm just not seeing it. Maybe on a very high revving engine "harmonics" can be a problem. That's definitely plausible, but on a 500hp 408 turning under 6500, I doubt it.

 

[rickstershemi]

haha! um both!

Rick, I attribute my longevity to amsoil!:cheers:
I've watched your car thread on moparts and I love what you're doing.
Welcome!

Seriously though guys...I mean no disrespect to anyone. I'm just kidding.
But fundamentally I hear a lot of things that it turns out simply just dont hold any water.

Same goes for cast cranks. I have heard for years how horrible they are, yet Brian H is building some damned good cast crank engines and putting people in the 10s, Not for a weekend either...with reliability!

The same can be said for anything. Elmiminate all of the variables that can cause something to fail that ordinarily wouldnt and you come to find that a lot fo things arent anywhere near as bad as people make them out to be through the rumor mill.

I am still waiting to see some evidence of how bad a geardrive is, and while I am waiting for that, all I am seeing and hearing is how good they are.:read2:

On my last motor I used a mopar timing chain which was supposed to be good. Well when I pulled it apart, it was hanging off the lower sprocket like a raw egg on a nail. It was all stretched out, I'm willing to bet if for some reason I turned the motor backwards it would have skipped teeth and gave me a really bad day...before the oil pressure issue would have. LOL

Let's get some more time with these things and see how bad they are. Thi way we have solid data if something is good or bad as opposed to pseudo-scientific speculation. I understand the theory trying be conveyed, but in practice I'm just not seeing it. Maybe on a very high revving engine "harmonics" can be a problem. That's definitely plausible, but on a 500hp 408 turning under 6500, I doubt it.

Totally agree and also with your comments on cast cranks....I'm went cast, for what I'm building that's all I need (not a fan of wasting $$$$) Proper part selection, accurate machining, balancing and assembly, builds longevity 8)

Now in my 565" Stroker I run top of the line $$$ parts....Jesel valve-train & Belt Drive at the top of the list 8)

Rickster

 

[POS Dakota]

Totally agree and also with your comments on cast cranks....I'm went cast, for what I'm building that's all I need (not a fan of wasting $$$$) Proper part selection, accurate machining, balancing and assembly, builds longevity 8)

Now in my 565" Stroker I run top of the line $$$ parts....Jesel valve-train & Belt Drive at the top of the list 8)

Rickster

Absolutely...in that roadster of yours with that power level the selection of parts necessary is a complete game changer.

I had Brian H at IMM do my heads and balance my assembly.
Based on his lack of **** talk and his positive delivery of results on the track, I have no doubts that this largely street driven engine will be just peachy.

 

[POS Dakota]

Absolutely no need for the rude potty mouth references. Everyone here seemed to be engaged in a really interesting conversation. I spoke what I know to be true......that is that the majority of serious racers do not run gear drives. I also gave the reasons. I could provide proof, but it wouldn't make any difference. You'd simply say it was not the fault of the gear drive. Hay, it's your money and your ride. Build it the way you want and have fun. But there's absolutely no need to get insulting and crude. I thought we were pretty much above that. All I did was offer an opinion based on experience of what I've seen. I offered that in good faith and with good intentions to provide another viewpoint. Simple as that. I didn't slam anyone for choosing to run a gear drive. I was civil in what I said. I expect the same in return.

I'm just having fun. I have no intention of being rude as you seem to know what you're talking about, and I do respect you. Don't take things out of context. But let's not cloud the distinction between a 500hp street engine, and a 750 hp race engine.

They are indeed two different animals and have completely different sets of requirements. Geardrive aside from it all, I would be using different heads, valvetrain, pistons, rods etc....

But even so...I know a few people making that 750 number at the wheels and they are using for example a stock block which is something largely frowned on. But it lives!!!! And I can prove it!

 

[POS Dakota]

Hey stroker scamp...

This is quite possibly an example of the elusive "valvetrain harmonics" issue....

But then again, this is a cast cam in a cummins diesel making 1191 hp and 2000 ft lbs of torque (looks more like 3000, but the dyno couldnt handle it) by a friend on my other forum. I would link you guys to it, but It's definitely not a family friendly group of people there. They're a pretty wild bunch of outspoken people, but indeed people who have a lto of experience making SERIOUS power.

Anyway just to make you feel better and recognize that I am not dismissing what you say, that if anything, this is probably attributable to valvetrain harmonics. But look at how much power the engine makes...

It's off the chart!!!! hehe
granted that's a cast cam core making that much power and if it took that much pounding to break something I'm not worried at all. That's my whole point.
Then again, I am unsure if a timing chain, or belt would live under that either.
So it's kind of a moot point. The gear looks pretty good though, dont you think? hehe

 

[POS Dakota]

Here's the actual vid of it in action...he was pushing 60 psi!!!!
watch the exhaust fan...LOL!

[ame="http://www.youtube.com/watch?v=tT7ukAyVyIc"]YouTube- ‪1191hp cummins‬‎[/ame]

 

[ne57]

Gear drives are no more accurate than a good timing chain. The crank and cam sprokets will stay in sync and in phase as long as the chain does not skip a tooth. PERIOD Because of the design of the chain and the nature of how the engine runs, it's impossible for the cam timing to vary from the crankshaft. While the engine is running, even of there's slack in the chain, which there is, even on a new one, the chain is always tight on the driver's side of the engine, because the crankshaft is pulling the chain and cam gear right along. There's no slop on the drive side of the chain. Want proof? Fire that pup up without the timing cover and see for yourself. I've done it quite a bit in diagnosis. Gear drives have only one advantage over a chain. They last longer. And with a high end chain and gearset, even that becomes arguable. A chain will eventually fail, although a good high quality billet double roller will probably not fail in your lifetime. Also, another known problem with gear drives is that they set up some freaky harmonics back through the entire valvetrain and can cause havoc with some forms of electronic ignition up through the distributor gear. They have even been known to cause some frequency interference with valvesprings at high RPM. THAT is something you don't wanna play around with. Can you say dropped valve @ 7K? Even computerized engines cannot run them because of this phenomena. They will slap booger up the knock sensor. What do the big boys run? Pro Stock, Funny Car and Top Fuel all run belts and chains. Ask around even the smaller classes. Nobody seriously into racing runs a gear drive, because the serious racers all know. Gear drives are nothing more than a gimmick fad to get into your wallet. I'll take a good chain anyday. Simple as that. Thank you. Drive through.

"They last longer". To me, that's not only about general condition before you have to replace it but also relative valve timing after alot of miles. The example you cite(tight on the pull side), while true when its new, I don't believe would still be true once the chain has worn. The springs would act as a drag and pull the cam retarded to the limit of the chain stretch.

BTW, I'm not sold on the idea that chains 'stretch', where the individual links grow longer due to ductility and tension. I think its more likely that the clearances on each wearing surface slowly open up due to friction and gives the impression of stretching. So, if that's true, and I can't swear to it, just a theory, what does that say about the oiling under the timing cover? Maybe the oil isn't getting where it should? And if the chain is wearing, where are those metal bits going? Scraping up the inside of your oil pump, opening those clearances too? Like said, I don't know for sure. But to me its reasonable that given that possibilty, if there's something you can do to reduce or eliminate that situation, at a low cost, maybe its worth doing.

So I'm going with the gear drive and adding in a more positive oiler, one that will spray directly on the moving parts, rather than 'hope' that the oil cloud will get where it needs to be.

Basically boils done to 'couldn't hurt'.

 

[ateam]

Gear drives, noisy/less noisy. Noisy is usually 20 deg. pressure angle(gear talk). Less noisy is usually 14.5 deg.(stronger). In the real world, as timing chains wear, the camshaft becomes more retarded. One need only look at all the tensioners included at the oem. level to attempt compensation of chain wear and "reverse accelleration", especially prevalent in 4 and 6 cylinder engines,(more room between the cam lobes). Let's look at the long term wear of the gen III hemi chain. I have have heard of straight 30 wt. oil will cause them to slap. Onward, ateam.

 

[rickstershemi]

Nothing against gear drives, some just want the blower drive sound....lol Me, not a fan and have run Cloyes DBL Rollers forever and to date have never worn one out ro had any timing issues......as stated previously, if it's an all out race effort I ould go straight to a belt drive......just my .02

Rickster

 

[POS Dakota]

Nothing against gear drives, some just want the blower drive sound....lol Me, not a fan and have run Cloyes DBL Rollers forever and to date have never worn one out ro had any timing issues......as stated previously, if it's an all out race effort I ould go straight to a belt drive......just my .02

Rickster

I definitely like the sound of gears rick. Since I was a kid in my chevy engines I have used the pete jackson. Always thought they were way cool.

You must be talking about the cloyes billet chain setup...the one with the holes only drilled in one side of the gear, right? I think they are around a buck fiddy if memory serves correct. If so, those are good.

I also like the JP rollmaster by I think Romac...the australian one.
I've used them before and it was good. I'm gonna use it in my wife's motor. Got it sitting right here on my desk.

But you're right, some like the gear sound and I also like the fact that I will never open the cover to find the chain hanging there and that my valve timing hasnt changed ove time. Granted that happened with a mopar chain, but it was enough where this is what I'm gonna stick with on this motor I plan on driving hard.

Belt drive...on a race motor, sure, since on a race motor, you're frequently performing checks on things all the time and if it's bad here or there, it can be replaced rather easily. Nice thing about those too is that you can change the timing pretty easily and get to it easily too.

But it's my thought that if you dont wanna go back in there on a motor you drive a lot, the gear is the way to go, at least for me it was. And like I said, I'm not planning on hitting 7000 rpm on purpose. I dont care about the harmonics. I care more about the cap walk! lol:read2:

 

[POS Dakota]

Well, looks like these crank keyways are 3 degrees +/- each.
I initially installed my cam in the straight up gear keyway and was 6 degrees off.
I pulled the gear (with a puller), reheated it, and installed it 2 keyways to the left and I am now sitting at a 106 degree ICL.

I also checked the intake opening and closing degrees @ .050 per the cam card and I am dead on. Now I know it will run the way it's intended. No offset keys necessary like stated by someone earlier to get to 106. To get 105 like Mad Dart needed would require it, but I honestly wouldnt care about 1 degree. 6 degrees off is enough to affect how it runs in a noticeable way though so I had to make sure. now I'm confident it's good.

The straight up keyway on the crank is the one with the little cat logo over it.
two to the left from there is +6 degrees. just so people know. I know I asked and no one knew. So there it is.

We're all good on the degreeing...time to get this ***** together....

When I installed the crank gear again I am still getting the .030 feeler in the space between the gear and crank step all around. I wish it would fit flush, but if other people are running 'em that way with no probs, I guess I will be no exception.

 

[POS Dakota]

WARNING!!!!

Make damned sure your crank gear is flush with the crank shoulder like so.

If you dont have it like this, the snout is going to snap off the crank!
If you go to the scat website and go into their FAQs IIRC they outline this.
I pulled my gear and chamfered it so it properly seats against the crank.

And yes I know some of you have had no problems and all that...that doesnt mean you WON'T!

Don't argue, just check it out and if you can fix it before you put your motor together or if you can easily get to it, fix it ASAP.

It will score a line around wherever it's binding against and snap the snout off right there.

Do this and you're good. If you look and find a scored line, polish it out, or it wont make a difference.

Also, notice now how mine is perfectly centered under the idler...this is how it's supposed to be.

This is how it was before and this is a problem! It had to be fixed. I chamfered the gear to clear the crank radius and now all is good. I recommend you do too.

FYI...don't wait until it happens to you.

 

[Mad Dart]

WARNING!!!!

Make damned sure your crank gear is flush with the crank shoulder like so.

If you dont have it like this, the snout is going to snap off the crank!
If you go to the scat website and go into their FAQs IIRC they outline this.
I pulled my gear and chamfered it so it properly seats against the crank.

And yes I know some of you have had no problems and all that...that doesnt mean you WON'T!

Don't argue, just check it out and if you can fix it before you put your motor together or if you can easily get to it, fix it ASAP.

It will score a line around wherever it's binding against and snap the snout off right there.

Do this and you're good. If you look and find a scored line, polish it out, or it wont make a difference.

Also, notice now how mine is perfectly centered under the idler...this is how it's supposed to be.

This is how it was before and this is a problem! It had to be fixed. I chamfered the gear to clear the crank radius and now all is good. I recommend you do too.

FYI...don't wait until it happens to you.

What did you use to do the chamfer?? Lathe or what?

 

[POS Dakota]

Nah, just some careful patient grinding with a carbide cutter, then a ruby stone to put a nice smooth radius all around. Then I test fit it a few times. Took some patience for sure.
but when I couldnt get a .001 feeler in there I knew it was good.

The way it is out of the box with that little angled bevel...soon as the balancer presses on it, it will eventually score a line into the radius on the crank snout and the balancer and pulley load will help snap the snout off.

With the gear keyed properly onto the crank only by the inside diameter and the back of the gear pressed against the shoulder, any improper stress of the crank snout is eliminated.

I just wanted to throw this out there before it happens to someone. I dont want it to happen to one of the guys who helped me, so I'm just returning the favor.

Dont be afraid to put a nice big round radius on there. Like I said, as long as it's properly keyed to the crank and pressed against the shoulder, you're good! That gear is strong.
Compared to a chain gear these things are some beefy stuff. So dont worry about being super precise, just make sure the radius is clear and you'll never have an issue.

the whole reason that radius is there on the snout is because a sharp 90 degree angle would cause it to snap off.
If there is a gear pressing into the radius and is scores a line, the whole purpose of the radius as a strength measure is eliminated.

 

[ne57]

POS Dakota, thanks very much for that. I will definitely check out my crank gear for that. Even though it seems to fit right looking from the outside, it couldn't hurt to check inside with some mach blue or something.

I must be blind but I couldn't find cat's FAQ page.

 

[comoxian]

Thanks for all of your input, POS.

ne57, I think that he meant he was looking at the "Scat" faq, the crank manufacturer.

But I don't understand how it could score the crank snout. The crank turns, the gear is pressed on and turns with the crank, not on the crank. How would it score a line on the crank snout?

I must be missing something.

And thanks for figuring out the keyway puzzle, POS.

Now to get back to building my engine.

 

[ne57]

Dohhhhh! there was speck of pizza on my monitor, didn't see the s in scat. :sign6:

Just a guess, but when the balancer gets torqued it maybe presses the gear into the crank and while not a wear pattern from movement might still make a slight groove or indent just from the clamping force. Who'd a thought that could be so deadly?

Still can't find the FAQ page, but then I'm web challenged.

 

[ne57]

Well finally! Here's some pics of my setup. I mentioned earlier about making an oiler for the bearing. While I was at it I made it squirt the teeth too. The two holes are .009". I had to grind down a .020" drill as that was the smallest I had.
The oil line was a brake line with the zinc stripped off, that I laser welded into the cam plate after drilling intersecting holes, so it feeds from the lifter gallery, I put a small hole in the gallery plug, I forget the size but somewhere around .020. A little oil resistant sealer on the back of the plate. After i lasered it i thought I might as well silver braze a fillet around the joint, extra insurance against a leak. Pulled the bearing for that. I lost the plating near the weld so I just removed the whole thing. I had to grind down the side of the cam plate near the bottom hole to clear the aluminum cover.
The crank gear fits flush and the gears all line up nicely. I did have to have the recess in the plate deepend by my machine shop, Now I have perfect cam end play. He did this gratis but what the hell I had just spent $2500 on machine work.

Timing the cam was tricky, since there's no dots and I don't have a cam card. I heard about a neat way to phase the cam... Find TDC on #1. Install two identical length lifters in the number six lifter bores. Slide a straight edge over the lifters. If exhaust lifter is higher then the cam is retarded, if intake lifter is higher the cam is advanced.
So what I did was install the stock chain and sprockets dot to dot, which puts me pretty close. Double checked with the #6 lifter trick. then pulled the stock set, installed the CAT without budging the cam. Here I had to eyeball which keyway would line up. You can see its not the 0 offest keyway with the cat logo. So after all that I checked the #6 lifter thing again and it was still where it was before. I then checked all the opening/closing points of the cam and the lobe centers. It looks like I'm maybe retarded ONE degree, which is nothing to worry about... still want to triple check all that. duration @ .050 is about 234 and lift is .450" at the valve. Looking at simliar cams I think I'm in the right ballpark as far as phasing the cam to the crank.

 

[ne57]

screwed that up. let's try the pics again...

 

[ne57]

well guess you can't see the cat logo, glare. The keyway that lined up was the second counterclockwise from the logo.

what else can i screw up here?