LA top end rebuild question

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https://www.hotrod.com/articles/looking-into-a-617hp-brazilian-nextel-cup-motor/

A modern, well engineered, high-strung small block which needs maximum power and durability uses a gear drive, especially to survive heavy engine braking. Strange. Maybe someone should tell him that they're 80 yr old chrysler is better designed.

There's also no modern manual transmissions using a chain or belt instead of gears... wonder if the designers know how much torque they're wasting? 4 chains must surely be better than 4 gears, right? Maybe we should be driving our rear ends with chains too - get rid of all those nasty gears robbing our torque.

Gear noise is a result of pressure angle. With proper design, a near-silent performance can be had with the proper pressure angle. Larger pressure angles are cheaper to produce/manufacture. Wonder why crap gear drives are loud? Proper pressure angles also allow the designer to avoid undercut gear teeth (which wear fast, are hard to cut, and are weaker).

Gears are near 100% efficient at transferring power when lubricated properly. Excess oil gets 'pumped' by the gears which takes power and causes heat. But addressing that is pretty trivial. Proper design gets around oil film issues.

The real troublesome part is proper gear alignment. A simple cost-effective method to adjust the idler is tough, and hitting perfect tolerances for a gear drive is a challenge but can be done by any competent machinist. Arriving at the proper setup can also be a challenge and requires highly accurate measurement of the engine block. Not hard if you know what you're doing though.

It's only when factory tolerances and field serviceability are taken into account that chains and belts begin to even make sense. We run them because they're cheap. They work well *enough*, but even at their best they're a compromise to deal with tolerance stacks and serviceability - and they do that part of the job better than gears.

The real question the OP needs answered is where on the quality spectrum does the Milodon system land? I'd be inquiring with Milodon about the pressure angle, and if it falls between 10 and 20 degrees it should be good to go - if it's noisy, then it's setup wrong if that's where the angle is set. The next question would be how hard is it to setup, and what is involved and what the typical failures are.
 




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Good Day everyone.
I am in progress of rebuilding/ replacing the top end on my 340. I plan to replace from the cam up. My question is - has anyone experienced installing a Milodon gear drive and if so how did it come out? Was it a worthwhile upgrade? I was toying with the idea of replacing my double roller timing chain and gear set with one of these. I know it is quite a bit more $ than the typical chain/ gear. I was thinking about the longevity of a gear set vs a chain/ gear set. My current timing chain is a bit stretched and should be replaced anyway.

Thoughts?

Thanks in advance.
72mopah, use this if the budget allows,
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Or this 'cause it's good
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But don't use this, 'cause it may be a deal, the deal is, it will look like this shortly
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Thanks for watching.
 
So by your logic: A manual transmission is faster than a new state of the art Automatic transmission right?

Those autos must be magic to work without gears. Let me know if you ever get to the point. Christ..

If gears are so horrible, why would a nextel team expend considerable resources and cost to run one? Because it sounds cool? Please..

Whether the gear drives available for Mopars are good versions would be an apt discussion, but instead this is all hot air internet "wisdom" being repeated as fact without any supporting evidence because no one has shared any so far.

Gears don't take more torque to turn and can be made quiet when designed right. It's simple engineering math and most machinists handbooks even have good guides. So, again, are any on the market designed right? Or are they designed to be noisy to be "cool"?

Everyone seems to wants to argue the basic concept (poorly) instead of answer the OP. The pertinent information is whether the milodon drive is a good one or not. I'd define good as both quality and quiet, because there's no engineering need to let it be noisy. All the videos and bloviating about "noise" has conveniently side stepped which brands are being shown or accused of excess noise. So, is the milodon drive good, or is it noisier than it should be?

I'm curious if @yellow rose has any input on which drives he would suggest and if all the available ones are noisy, or if there's a trick to proper setup?

But by all means, if everyone wants to just keep up with the chest thumping, I'm sure the OP will be entertained even if members here only further prove how worthless internet "advise" can be.
 
Th.

If gears are so horrible, why would a nextel team expend considerable resources and cost to run one? Because it sounds cool? Please..

Most everything under the hood of my car was done at a local NASCAR Shop. Tony Hirshman's. is a good friend and his son Tony is the spotter for Kyle Bush. My first small block in the Duster came from Ray Everingham racing from an old mopar NASCAR truck. They were all using chains. Why make up stories? Recently Kyle was trying the new gatorback belt drive belt timing sets. Due to harmonics because of switching to EFI. They tried but never used gears because of the power/torque loss off the turn.

The world of Outlaw cars use gears because they run the oil pump on the front of the cam, Power steering and "methanol manual fuel injection pump not EFI"off of the back of the cam. Running those accessories off of the cam you need a gear drive for 50 to 100 laps max. A good friend and neighbor runs a 410 sprint car. You are talking to a 64 year old man who has been around all types of race cars including Top fuel. since I was 18 yrs old. But it is out with the old and in with the new. I saw the light.

Bottom line is gears drives suck on a street car. The gears may last but the Harmonics/vibrations will destroy a motor over time. Including the gears as shown above. God gave us all a brain to use . Engage yours and the lights will turn on for you also.

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To the op pay a little more and get a quality chain and gear set. This is mine roll master vernier type !
 
Why make up stories?
What stories? You obviously did not read my link.

Recently Kyle was trying the new gatorback belt drive belt timing sets. Due to harmonics because of switching to EFI. They tried but never used gears because of the power/torque loss off the turn.
Loss of torque to drive the gears, or because of efi issues? I'm betting the latter.
If it was the gears, should be easy to overcome, especially with a dry sump. Gears can only take more power away if they're pumping oil. Tons of engineering math goes against gears taking more torque to drive otherwise.
EFI issues would probably have more to do with the spec electronics than the gear drive and would also explain the quick change to something else that "just works".
Electronics are finicky that way and NASCAR is known for not being so state of the art.

The world of Outlaw cars use gears because they run the oil pump on the front of the cam, Power steering and "methanol manual fuel injection pump not EFI"off of the back of the cam. Running those accessories off of the cam you need a gear drive for 50 to 100 laps max. A good friend and neighbor runs a 410 sprint car. You are talking to a 64 year old man who has been around all types of race cars including Top fuel. since I was 18 yrs old. But it is out with the old and in with the new. I saw the light.
None of this ^
Is relevant to this:
Bottom line is gears drives suck on a street car. The gears may last but the Harmonics/vibrations will destroy a motor over time. Including the gears as shown above.

How? No one has ever explained how, yet it keeps getting repeated. Makes zero sense from a design standpoint. Lots of folks run them successfully and quietly and report no additional wear resulting from them.

Being around others or knowing guys who run gears grants zero authority on engineering and design matters. I'm sure those sprint teams aren't tossing gear drives every race.. So I'm willing to bet they last longer than implied.
It also makes sense to run gears to deal with the increased load on the cam from accessories - but that only implies that they'd be overkill on the street - NOT that they'd turn an otherwise high output engine into a time bomb.
Why would they use a cam drive system that would be slowly killing such an expensive engine? My bet is that it doesn't kill the engines, otherwise they'd just gear down an external accessory drive for those items. A small planetary box could easily drive off the crank at half speed and still keep the engine package tight. Hell, it could also lower CG... But since they don't do that, my guess is that using gears and cam drive is not such a risk as you suggest.

God gave us all a brain to use . Engage yours and the lights will turn on for you also.

If I used my brain twice as much as you, I'd hope they'd pull the plug on me.
 
Well since the moderator cleaned up this thread (for the most Part), good.
It seems to me the ones with the most racing and engine building experience have pretty much said what I said.
I'm no engine builder just a DIY kinda guy, but I've rebuilt maybe 5-6 motors in the past 20+ years, and all of them didn't "blow up" or "fail" because of chains.
2 of those motors are high performance and one was in a Ramcharger that towed a 5000 lbs trailer alot.

Do chains stretch out? Well duh yeah but that takes awhile, but it's not rocket science to check your timing.
Here's another example: Why are almost all the Superbikes chain driven? Cruisers are mainly belt driven now, quite a few of them did away with shaft driven gearbox.
Kinda makes you think...

And yes I used to be part of the 4X4/jeep crowd. If you're not doing any extreme rock-crawling, Moab running, or mud-racing, the chain transfer case is just fine.
Chain driven Transfer cases are still used by 70% of the offroad Jeep crowd. (Now if your counting the grocery couriers and mall cruisers that number jumps to over 90%)
And yes I used to be in these forums: NAXJA (North American XJ Assoc.) Pirate 4X4. and RCC (Ramcharger Central).
For that crowd if your rig is mainly general purpose let say 60/40 (street/offroad) or 70/30 or more, most of them stuck with chains.
For a trail only trailer queen yes most of those are gear driven transfer cases.
I would not advise Pirate4X4, there were a lot of douche-bags in that forum but again that was 10 years ago.
The "big 3" of Jeep Transfer cases is the venerable Dana 300 (Gear), the NP/NV 231 (Chain), and the latest I heard is the NP241OR "Rocktrac" (Also chain)
The NP241OR is reputed to be the strongest of the jeep TF's (Reputed to withstand the torque of a Cummins)

There was maybe only one geared timing, I heard in person that wasn't bad. But he drowned his out with true dual exhausts with Flowmaster 10's dumped before his rear axle, in his 400 SB 73 El Camino.
Riding for 20 minutes at 2500+ rpms with no ear-plugs. I needed a Tylenol after that. Yes I'm getting old

I really want to see a video of these so-called quiet gear driven timing, as well as know their setup. Curious to know what options us Mopar crowd have, which isn't much.
 
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Question was anyone set one up and how did it go and was it a worthwhile upgrade? Ill say yes to both. It takes a motor on a stand to install correctly as you have to mock it up and then mark the bolt you have to drill and tap. You also have to get the backlash correct (iirc 6-8 thou) and its no fun in the car. To set backlash they use a piece of newspaper between the gears and then you press the gears together and then tighten top bolts, then you drill and tap the new bottom hole. Bottom hole is more for saving your lash and very small adjustments. using a mic afterwords to make sure your between 6 and 8 thou. CAT used to make a decent one but its long out of production. IIRC Milodon is the only game in town for the LA Mopar.
 
I guess I'm stupid, but what's the lock collar you keep talkin about?
I believe a lock collar is a **** ring for your distributor shaft. It prevents the distributor/oil pump drive from walking up and down on the cam helix, altering the distributor timing. Has jack to do with valve timing.
 
72mopah, use this if the budget allows,View attachment 1715405134
Or this 'cause it's good
View attachment 1715405136
But don't use this, 'cause it may be a deal, the deal is, it will look like this shortly
View attachment 1715405137
Thanks for watching.
Pete Jackson gear drives are a joke. The fact that the idler assembly moves with the direction of force (the have a drive gear and a coast gear) makes it a noisy affair even at idle. single idler systems are superior as there is no floating gears. These are popular because they are $69 for a SBC. Ran one on a Cleveland and a 451 Mopar. Both had a blower drive sound to them. Milodon gears are cut much better and the material is superior.
 
Question was anyone set one up and how did it go and was it a worthwhile upgrade? Ill say yes to both. It takes a motor on a stand to install correctly as you have to mock it up and then mark the bolt you have to drill and tap. You also have to get the backlash correct (iirc 6-8 thou) and its no fun in the car. To set backlash they use a piece of newspaper between the gears and then you press the gears together and then tighten top bolts, then you drill and tap the new bottom hole. Bottom hole is more for saving your lash and very small adjustments. using a mic afterwords to make sure your between 6 and 8 thou. CAT used to make a decent one but its long out of production. IIRC Milodon is the only game in town for the LA Mopar.
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Newspaper to set backlash.
Never heard that one.
I remember back in the day everyone used a match pack to set their points.
 
Its legit, right there in the manual:
"....You can now proceed with the backlash adjustment. Use a single strip of newsprint (not gloss magazine paper) 1/2" wide x 6" long, and wrap the newsprint around the idler gear, between the cam gear, idler gear and crank gear. Press the mounting plate and idler gear assembly firmly by hand toward the cam and crank gears , being sure the newsprint is in place. This centers the idler gear between the other two gears as well as sets the lash between two pairs of gears all in one procedure. A dial indicator while appearing more high tech, can not accomplish all these procedures...."
Although in the end they say if you want to check backlash with a mic, it should be .006-.008 on each pair of gears so is that .012-.016 measuring the cam gear to the stationary crank gear? IIRC I got mine .007 from crank to idler. I think this setting is all you can adjust. Ooh, i just found my vid still on my phone from over a year ago! Along with the general area of the tapped bolt hole. Someone tell me if this is correct or do I measure off the cam gear? It's still apart so no harm done.
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I'm now questioning my placement of the dial indicator on the gear itself to measure backlash..maybe more at 90 degrees from mesh and to dial probe?
 
Someof the gear drives were made noisy intentionally because street punks back in the day thought it was cool. Pete Jackson units come to mind
Like Thrush stickers in 1/4 windows.
easy :icon_fU:

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