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Milodon Gear DRive |
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White70JavelinSST 
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Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4867 |
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 Posted: Feb/20/2019 at 8:17am |
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Well, that does it, I guess I got screwed over royally by buying a relatively unused gear drive for less than 1/4th the cost of new. Live and learn... |
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70 Javelin SST, second owner, purchased 1972
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needafasterAMX
AMC Addicted 
Joined: Feb/20/2008 Location: TLH,Florida Status: Offline Points: 724 |
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Posted: Feb/20/2019 at 6:29pm |
they are junk. you wasted you $$$$ I'll take it off your hands
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74 AMX, 401
Viper spec T56 6 speed trans Hydroboost brakes with rear disks from a Avenger 3:73 TG rear,now Trutrac with 3:15 A Turbo is in my future. |
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Buzzman72
AMC Addicted
Joined: Sep/15/2009 Location: Southern IN Status: Offline Points: 2726 |
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Posted: Feb/20/2019 at 7:03pm |
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International Harvester used gear drives on every one of their V8's. Unlike Pete Jackson gear drives, they used helical-cut gears, and no idlers. They weren't particularly noisy, and the recommended engine redlines were 4400-4500 rpm. Many of these engines ran past 200,000 miles with regular maintenance. So just the fact that it's a gear drive isn't the biggest problem. The problem is, these engines were engineered with a gear drive in mind (camshafts are "reverse rotation," compared to chain or belt driven cams, for example), and most passenger engines are not.
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Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.
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SC397
AMC Addicted
Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5480 |
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Posted: Feb/20/2019 at 7:55pm |
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Well, IH didn't use gear drives on the V8 engines that they bought from AMC..
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Buzzman72
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Joined: Sep/15/2009 Location: Southern IN Status: Offline Points: 2726 |
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Posted: Feb/20/2019 at 8:08pm |
True. Which brings us full circle.
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Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.
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amcenthusiast
AMC Addicted
Joined: Jul/02/2012 Location: SW Atlanta GA Status: Offline Points: 1778 |
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Posted: Feb/20/2019 at 8:44pm |
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My first thought is the gear drive setup is for steel billet roller cam with triple valve springs...
...where the double roller chain would be known to be stressed past the rated limit. I learned this while doing research in order to make a roller timing set for Rambler V8; reading all info I could find about chain drive systems on websites like Morse Chain. -The way the rollers on a roller chain enter a well designed sprocket is made for smoothness and long lasting durability. A lot of science goes into designing chains and sprockets for their expected load and rpm. -makes a stock type link belt look silly by comparison. Concern for harmonic transmission between the crank and camshaft explains why so many engines came with a nylon toothed upper cam gear. Straight cut gears are known to be more harsh running than helical cut gears. (Studebaker V8 design has 'short deck height' with helical cut direct drive cam gears... apparently like the International Harvester blocks) I've got more to say on this topic but I'm gonna take a break and see if I can find the excellent website having extensive roller chain information... |
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443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/ |
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Red Devil
AMC Addicted
Joined: Jul/10/2007 Location: Canada Status: Offline Points: 1743 |
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Posted: Feb/20/2019 at 9:30pm |
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IIRC, the GM 2.5 Iron-Duke in my '80 Spirit had timing gears and no idler - direct drive from crank to cam ... helical not spur gears. RPMd higher than the stock AMC 6 cyl or V8.
Timing belt is likely best, but only seen pictures of one or two custom ones on AMC V8s.
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amcenthusiast
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Joined: Jul/02/2012 Location: SW Atlanta GA Status: Offline Points: 1778 |
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Posted: Feb/20/2019 at 9:32pm |
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Video on chain technology 101;
= there's only so much chain that can fit inside the stock timing cover* & when the rated limit is exceeded, a gear drive system may be an option. *smaller rollers and smaller links actually have higher rpm capability. Therefore to get more strength, multiple rows are added. This makes the chain become wide. Eg: a double roller chain vs a single wide chain.
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443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/ |
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amcenthusiast
AMC Addicted
Joined: Jul/02/2012 Location: SW Atlanta GA Status: Offline Points: 1778 |
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Posted: Feb/20/2019 at 9:43pm |
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Basically chains are 'the opposite' of what a 'newbie' might guess to be 'high performance' -where 'big links' are rated for slower rpm and 'small links' are rated for higher rpm... check out Martin Sprocket charts: www.martinsprocket.com/.../sprocket-engineering-data---horsepower-ratingsfeccaacbf-so when a smaller link chain is needed for higher rpms, more rows are added, which increases the width of the chain (and adds more sprockets)
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443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/ |
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amcenthusiast
AMC Addicted
Joined: Jul/02/2012 Location: SW Atlanta GA Status: Offline Points: 1778 |
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Posted: Feb/20/2019 at 10:00pm |
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A roller chain will reduce friction compared to a stock type link belt; the rollers are like wheels that turn as they enter and exit the teeth on a sprocket.
The friction reduction raises engine oil quality -less shearing, less heat input. The straight cut gears with higher valve spring rates will demand high EP (extreme pressure) quality oils, to prevent excessive wear, potential galling. Juxtaposed to a helical cut gear set, since there is very little scrubbing action between the teeth of a straight cut gear set, there is reduced mechanical action to draw in lubricating oil -for cooling the contact surfaces where the gears mesh together. -the calculated scrubbing action of a spinning 'flat tappet lifter' (convex lifter face surface area) upon a cam cut with lobe taper is an excellent example of this lubrication tactic, also a rocker tip scrubbing back and forth on the tip of a valve stem: without the scrubbing action, new cool lubricant would not be drawn into the scrub area, the oil would suffer thermal and molecular breakdown, with galling from metal to metal contact very likely.
Edited by amcenthusiast - Feb/20/2019 at 10:03pm |
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443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/ |
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White70JavelinSST wrote: