Regarding solid timing gears.

[TOBASH]

For those of you rebuilding these engines and such:

FYI:

A P400 build utilizing a Leroy’s solid gear setup has failed in a routinely used but not abused H1 DS4 rig. Low mileage. P400 was purchased new from RubberDuck.

(was NOT my rig.)

The dogbone broke apart.

 

[sbgarage]

That is a shame. I'm going to assume it took the engine out.

 

[87cr250r]

The gears and plates don't look heat treated in the advertisement picture, they're too bright. The failed gears are obviously not hardened because the edges of the teeth are rolled over. A properly heat treated gear should break a tooth with minimal plastic deformation.

It's also a big risk adding bushings and gears to a system designed for a splashed lubed chain. Gear drive conversions have been around for the gas engines for some time. Has anybody actually put miles on an engine with one?

Straight cut gears introduce a lot of vibration.

 

[TOBASH]

That is a shame. I'm going to assume it took the engine out.

Yes

The gears and plates don't look heat treated in the advertisement picture, they're too bright. The failed gears are obviously not hardened because the edges of the teeth are rolled over. A properly heat treated gear should break a tooth with minimal plastic deformation.

It's also a big risk adding bushings and gears to a system designed for a splashed lubed chain. Gear drive conversions have been around for the gas engines for some time. Has anybody actually put miles on an engine with one?

Straight cut gears introduce a lot of vibration.

Agree 100%

I wonder if the gears are manufactured in the East in a hostile Asian country with a five letter name.

 

[Mogman]

As a general rule these kits that replace chains with gears are a failed venture.
They cause harmonic vibrations that end in failures like these and even breaking the drive end of the camshaft off.
If for some reason you want to run these a very good fluid damper is mandatory but does not guarantee that harmonic failure will not occur.
This has been a well known issue in the hotrod community for a couple decades at least.

 

[87cr250r]

There is a reason OE timing gears are helical and not straight cut. Vibration.

 

[TOBASH]

Interesting discussion here.

Seems to me that for anything other than a tractor pull on an engine that is repeatedly rebuilt after limited use, chains are the way to go. Yes, they occasionally wear and stretch and even break. Still OE chains seem to be the best way to go overall.

EDIT - read my post #10 below.

 

[FlameRed]

I watch all those hot rod show on the tele and every once in a while I see them throw in these timing gear sets instead of chains.

They always mention how hard they are to find, and they used to be widely available back in the 80's. Now I know the reason why they are so hard to find! Another oddity is that these shows don't usually spend a lot of time talking about parts that the show is not paid to promote. I guess the reason is the cool factor is supposed to be is they sound like a supercharger when installed. They don't care what blows up off screen!

 

[gringeltaube]

...... The failed gears are obviously not hardened because the edges of the teeth are rolled over. ..........

..... Or is it that they just didn't bother to deburr those edges, after milling ?? Meaning these simply are some el-cheapo aftermarket parts... (!)

For what it matters, shape of teeth still looks normal to me. If they really were "rolled over" I think edges would look different, drive vs. coast side of each tooth. Not ?

Seems to me that for anything other than a tractor pull on an engine that is repeatedly rebuilt after limited use, chains are the way to go. Yes, they occasionally wear and stretch and even break. Still OE chains seem to be the best way to go overall.

Totally agree! Although I've yet to find a 6.2 or 6.5 which actually broke its timing chain.

BTW, I would love to hear which manufacturer/ brand is the best our money can buy, nowadays. (??)

 

[TOBASH]

..... Or is it that they just didn't bother to deburr those edges, after milling ?? Meaning these simply are some el-cheapo aftermarket parts... (!)

For what it matters, shape of teeth still looks normal to me. If they really were "rolled over" I think edges would look different, drive vs. coast side of each tooth. Not ?

Totally agree! Although I've yet to find a 6.2 or 6.5 which actually broke its timing chain.

BTW, I would love to hear which manufacturer/ brand is the best our money can buy, nowadays. (??)

Apparently our 6.2 and 6.5 Detroit Diesels are somewhat atypical. I was just taught that most Diesel engines are solid gear designs. (Yeppers, I don’t know everything and I still can learn).

Our units use chains for reasons of sound reduction, size reduction, weight reduction, and cost and because this engine is an attempt to use an OHV 8 cylinder block similar to a BB Chevy as a Diesel engine.

I now understand the drive to place a solid gear design and the reasons behind why we have a chain drive instead.

Still, I’m not comfortable with the fact that there are reportedly and allegedly failures in the Leroy system. Chris at Twisted Steel posted on another forum that he has seen a few failures. To be fair, others say the failures are due to incorrect installation.

I’ll just keep my chain until a major player like AMG or Detroit Diesel or GM designs and manufactures one in the USA.

 

[Mogman]

Apparently our 6.2 and 6.5 Detroit Diesels are somewhat atypical. I was just taught that most Diesel engines are solid gear designs. (Yeppers, I don’t know everything and I still can learn).

Our units use chains for reasons of sound reduction, size reduction, weight reduction, and cost and because this engine is an attempt to use an OHV 8 cylinder block similar to a BB Chevy as a Diesel engine.

I now understand the drive to place a solid gear design and the reasons behind why we have a chain drive instead.

Still, I’m not comfortable with the fact that there are reportedly and allegedly failures in the Leroy system. Chris at Twisted Steel posted on another forum that he has seen a few failures. To be fair, others say the failures are due to incorrect installation.

I’ll just keep my chain until a major player like AMG or Detroit Diesel or GM designs and manufactures one in the USA.

It is not a matter of who makes it, the issue is common to all "kits" that use this design gas or diesel, the only alternative would be to build a type of gear drive with two gears one on the crank and one on the cam which is what all factory gear driven cams but for the two stroke diesels use, it is not a V8 issue.
The problem with a gear drive like the V8 Ford Power Stroke uses is the cam and oil pump would have to be re-designed because it would turn them backwards as the cam and crankshaft turn in opposite directions, this is why you cannot use any of the IPs off of them on a 6.2/6.5L.

Cam chain failures is not a big concern on the 6.2/6.5L as there are plenty of other shortcomings to worry about.

The 2 stroke Detroits us an intermediate gear set so that engine is easily converted from right hand to left hand rotation, part of the genius by the engineers that designed it.

IMHO if it were not for environmental regulations the 2 stroke diesel would still rule the highways and waterways.
The old Chris Craft Roamer I owned in the 80s had twin 8V53 Detroits one right and one left hand turn and it was bad to the bone.

 

[Mogman]

Unfortunately GM has always been ruled by the need to have a "quiet" engine.
This is the reason for a cam chain on a V8 GM engine, to make it even worse they made it quieter by having nylon teeth on the cam gears, that is why they would fail at about 100K in the early gas motors, this is also why GM decided on indirect injection on the light/med duty diesels as it was quieter than the mechanically injected direct injection diesels.
Dodge went to Cummins and all their engines were direct injection, this is the biggest reason you can turn up the earlier mechanically injected Dodge engines.
Ford followed GM somewhat by using IDI on the 6.9L and the early 7.3L and that is why those engines have a very limited power potential.
In 1994 the 7.3L went to direct injection and that is why they are sought out for mods.
BTW all International V8 engines that were first introduced in 1955 had gear driven cams and a 360 rear seal, GM did not introduce the 360 seal on their V8 auto engines until the late 80s when extended factory warranties started to cost the FACTORY money to replace them.

 

[TOBASH]

Thank you for the interesting info Mog

 

[87cr250r]

The GM engine was intended to be a light duty engine. It needed to be inexpensive. It also needed to run like a gas engine with a broad torque curve. It didn't make a lot of torque but it could rev out to 4k rpm which the DI engines couldn't.

The single hole pintle nozzles were inexpensive to produce. I wonder if the aerospace alloy, possibly Nimonic combustion chambers offset that price?

 

[sbgarage]

There is a member on diesel place that is looking for one of these units to study and improve if someone is willing to donate their timing set or has one on a shelf

 

[sue]

From the picture it appears that the “gear teeth “ have a very poor fitting or
engagement. Straight cut gears should wear in a “wiping “ movement.
These don’t appear to engage at more that half?

 

[87cr250r]

Involute gear teeth don't slide against each other, they roll. Here is an article on how properly constructed gears fail.

Google Image Result for x-raw-image:///6170dd5931167da9bed2df9c41b9a2687bc264c9d840695bcbda83183e39d7df

See "Plastic Flow" on page 10.

I operate a fleet of tugboats and during my career we have moved away from conventional gearboxes with helical gears to z-drives which are exclusively palloid gears. The helical gears were 18-24 inches wide and extremely sensitive to misalignment. We experienced a lot of corrective pitting due to misalignment from bearing outside race rotation wearing away the housings. Now, with palloid gears (helical bevel) they are extremely tolerant of misalignment and we no longer see pitting. Instead the shafts start moving around so much radially the lip seals can't keep the water out of the gearbox.