T-III Reliability improvement

[turbovanman²]

Hard to see in the picture, but is that pulley keyed?

Yep, its the same one in the engine pics, I must have the keyway facing the camera.

[omnigoestohell]

Thanks Ken, glad to see you pop in here --- the concept of the amplitude of the differential in spring rates coming into play in shearing the teeth is an interesting additonal aspect to contemplate.

Have you, or do you know anyone who has used an idler-sized tensioner on the front and a increased diameter sprocket as you were suggesting?

Does the additonal tooth engagement (2 teeth?) on the intake cam by using an idler/tensioner up front make enough of an impact that you think it would play a role in fixing the belt problems?

Do you think these changes were well known within Chrysler back in the early-mid nineties (but deemend too expensive or complicated to implement to a fleet of several thousand cars through a TSB) or is this something that was learned through the development of the later twin cam motors and SRT4?

Any thoughts on what is more likely the oil pump killer -- the tension on the end of the belt end of the the intermediate shaft or the speed at which the shaft and pump are made to turn? The front idler addition without changing the sprocket diameter would address the concern of reducing some of the bearing loading on the pump shaft but it seems difficult to determine which is causing the pump failure --- shaft movement from bearing failure or pump failure from over speed/lubrication issues.

Note that valuable belt length is being consumed. To counter-act this without the need for tensioner relocation, compare a production idler pulley to a tensioner-pulley and a significant commonality becomes apparent. The outer bearing race hub OD, on the idler, is incredibly close to the inner bearing race hub of the tensioner-pulley. With careful machining the outer tensioner-pulley OD can be eliminated and an adjustable idler is the result. This modified tensioner can be used in the standard location for an increase in usable belt length and also provides an additional belt/cam angle adjustment point, when installed on the front side of the engine. Adding an idler with minimal reverse flex loading while providing some increase in cam pulley belt wrap is a considerable improvement; while thorough rotational torque load reduction, balance shaft removal, and oil pump speed reduction can secure proven gains in durability.

I hope this helps.
Thanks

[Ondonti]

I would be fine with splitting the difference. If you are unwilling to change timing belts on schedule with a TIII then sell it to someone who will! Rare cars are not for the lazy person who wants to put big mileage on them.
Then do Jackson's pulley mod. I really wouldn't have a problem with keeping the stock install height if the only worry is the timing belt. As long as the intermediate shaft can be made to survive, that is what I would care about.

[Lotashelbys]

Does the additonal tooth engagement (2 teeth?) on the intake cam by using an idler/tensioner up front make enough of an impact that you think it would play a role in fixing the belt problems?
.

Im sure the extra belt wrap helps but I did this idler mod more to put an idler between the intake cam and the I-shaft. I thought it would help on any unwanted harmonics that were created between that run of the belt. I would say it helps out more in the life of the I-shaft and pump teeth and the I-shaft bearing life. I also noticed that I could run less tension when running them with the idler in the front. I would think that would help on bearing life.

Any thoughts on what is more likely the oil pump killer -- the tension on the end of the belt end of the the intermediate shaft or the speed at which the shaft and pump are made to turn? The front idler addition without changing the sprocket diameter would address the concern of reducing some of the bearing loading on the pump shaft but it seems difficult to determine which is causing the pump failure --- shaft movement from bearing failure or pump failure from over speed/lubrication issues.

I really think it more to do with belt tension. Every failure I have personally dealt with(not my own) has proven to be way too loose of a belt. I checked a few of them with the gauge before I pulled them apart and two of them were right at 45LBS. I was almost thinking that there is a certain number that causes just the right harmonics to cause the failure. Almost like how a certain frequecy will break glass I think its the same concept here. I have even seen a few pumps break off at the mounting flange instead of sheering teeth.

Another thing that I have been wondering is has anyone had the warranty shaft ever strip out on them? Its the one starting with the 466 P/N. My first TIII car I owned had a very loose belt for the first few years didnt have any issues but had the 466 shaft in it. I wonder if that saved it?

[Lotashelbys]

Ken
What are your thoughts on the idler relocation? When we talked at SDAC 19 it was almost like you didnt think it would work or have any advantages. I should of showed you in person cause we brought 3 TIII cars down from WI that had that done to them......

[Pat]

Im sure the extra belt wrap helps but I did this idler mod more to put an idler between the intake cam and the I-shaft. I thought it would help on any unwanted harmonics that were created between that run of the belt. I would say it helps out more in the life of the I-shaft and pump teeth and the I-shaft bearing life. I also noticed that I could run less tension when running them with the idler in the front. I would think that would help on bearing life.


I really think it more to do with belt tension. Every failure I have personally dealt with(not my own) has proven to be way too loose of a belt. I checked a few of them with the gauge before I pulled them apart and two of them were right at 45LBS. I was almost thinking that there is a certain number that causes just the right harmonics to cause the failure. Almost like how a certain frequecy will break glass I think its the same concept here. I have even seen a few pumps break off at the mounting flange instead of sheering teeth.

Another thing that I have been wondering is has anyone had the warranty shaft ever strip out on them? Its the one starting with the 466 P/N. My first TIII car I owned had a very loose belt for the first few years didnt have any issues but had the 466 shaft in it. I wonder if that saved it?

Did those two with pump/ishaft failure also have stock retainers in them?

[Lotashelbys]

Did those two with pump/ishaft failure also have stock retainers in them?

Those did IIRC. Although I have heard of a few that failed with Titaniums in them. I checked with the owners of thoe and they told me that they didnt use a gauge and the belts were in fact loose.

[5DIGITS]

Ken
What are your thoughts on the idler relocation? When we talked at SDAC 19 it was almost like you didnt think it would work or have any advantages. I should of showed you in person cause we brought 3 TIII cars down from WI that had that done to them......

Good to hear from you!

I support the idea of having something to touch the belt as it doesn’t take much contact to have an impact on belt resonation/oscillation. On the other hand packaging does come with its limitations and does contribute to where it should or could be placed.

Additionally, I saw a post asking whether the added contact, on the intake cam, was worth it. This would rely on the extent of valve-train modification. If the spring rates have been sufficiently addressed, the impact is reduced. On the other hand, it would be greatly welcomed on an engine with upper-tolerance spring rates and corresponding load.


Keep in touch.

[5DIGITS]

Got it...thanks for clarifying.

I see the advantage lowering that spring pressure further, but at what closed pressure and rpm does float become a concern? Based on the valve size and lift, is there a closed spring pressure that you're targeting?

I've run the raised retainers the vendors sell for years, which I think raises the spring height .070" and have had no belt, oil pump or I shaft bearing issues. I've also had no valve float issues running to 7000 or so. I'm wondering at what point does the float risk outweigh the benefits of lightening the spring.

The best target is the lowest level of differential spring rate that provides the greatest return for the modification being made.


Stock CLOSED valve pressures:
The 8V roller installed spring rate: 110-120lb.
The T-III roller installed spring rate: 115-127lb.

Stock OPEN valve pressures:
The 8V roller peak spring rate @.430”: 200 - 215lb.
The T-III roller peak spring rate @.335”: 250 - 275lb.

Please notice that the following occurrences are based on nominal spring rates.
An 8V spring goes from approx. 115lbs @ 0” lift to 207lbs @ .430” lift.
This is a differential pressure of 92lbs

A T-III spring goes from approx. 121lbs @ 0” lift to 262.5lbs @ .335” lift.
This is a differential pressure of 141.5lbs

The aggressive characteristic of the T-III spring realizes a greater change in pressure as the valve is compressed and less change in pressure as it nears its free-length and therefore is able to exceed twice its spring pressure, within a shorter travel distance. This is accomplished even though the springs are within 6 lbs of each other when the valve is closed. The impact level of .075” and the considerations of increased offsets are now realized.

It would not be unreasonable for the smaller T-III valve to be run near the early T-II spring spec of approx. 90lbs due to spring characteristics, having a lower peak lift and being a smaller valve.

In this case:
A T-III spring now goes from approx. 90lbs @ 0” lift to 190lbs @ .335” lift.
This is a differential pressure of 100lbs
This equates to a 30% reduction in differential loading while functioning within 8V specifications.
This also explains how a smaller valve realizing less lift can support 7000+RPM while improving belt durability.

Thanks

[turbovanman²]

Stock one's I measured were 120 closed, 240 open.

The springs on my head are 78 closed, 150 open.

I was looking up SRT specs and most aftermarket ones are around 188-220 ish open.

[Pat]

The best target is the lowest level of differential spring rate that provides the greatest return for the modification being made.


Stock CLOSED valve pressures:
The 8V roller installed spring rate: 110-120lb.
The T-III roller installed spring rate: 115-127lb.

Stock OPEN valve pressures:
The 8V roller peak spring rate @.430”: 200 - 215lb.
The T-III roller peak spring rate @.335”: 250 - 275lb.

Please notice that the following occurrences are based on nominal spring rates.
An 8V spring goes from approx. 115lbs @ 0” lift to 207lbs @ .430” lift.
This is a differential pressure of 92lbs

A T-III spring goes from approx. 121lbs @ 0” lift to 262.5lbs @ .335” lift.
This is a differential pressure of 141.5lbs

The aggressive characteristic of the T-III spring realizes a greater change in pressure as the valve is compressed and less change in pressure as it nears its free-length and therefore is able to exceed twice its spring pressure, within a shorter travel distance. This is accomplished even though the springs are within 6 lbs of each other when the valve is closed. The impact level of .075” and the considerations of increased offsets are now realized.

It would not be unreasonable for the smaller T-III valve to be run near the early T-II spring spec of approx. 90lbs due to spring characteristics, having a lower peak lift and being a smaller valve.

In this case:
A T-III spring now goes from approx. 90lbs @ 0” lift to 190lbs @ .335” lift.
This is a differential pressure of 100lbs
This equates to a 30% reduction in differential loading while functioning within 8V specifications.
This also explains how a smaller valve realizing less lift can support 7000+RPM while improving belt durability.

Thanks

Great info...thanks.

[5DIGITS]

Thanks Ken, glad to see you pop in here --- the concept of the amplitude of the differential in spring rates coming into play in shearing the teeth is an interesting additonal aspect to contemplate.

Have you, or do you know anyone who has used an idler-sized tensioner on the front and a increased diameter sprocket as you were suggesting?

Does the additonal tooth engagement (2 teeth?) on the intake cam by using an idler/tensioner up front make enough of an impact that you think it would play a role in fixing the belt problems?

Do you think these changes were well known within Chrysler back in the early-mid nineties (but deemend too expensive or complicated to implement to a fleet of several thousand cars through a TSB) or is this something that was learned through the development of the later twin cam motors and SRT4?

Any thoughts on what is more likely the oil pump killer -- the tension on the end of the belt end of the the intermediate shaft or the speed at which the shaft and pump are made to turn? The front idler addition without changing the sprocket diameter would address the concern of reducing some of the bearing loading on the pump shaft but it seems difficult to determine which is causing the pump failure --- shaft movement from bearing failure or pump failure from over speed/lubrication issues.

Idler tensioner and front sprocket:
Yes and the adjustment capability served well by supporting multiple purposes.
The popular use of an 8V pulley does work and it has been successfully utilized.
The added steps required to use the various adjustment pulley parts is entirely up to the desired level of component accuracy. Knowing the parts exist to accomplish this is a good foundation for a potential future item.

Additional concepts tested:
A center idler was an approach that had the belt coming down between the sprockets. This used a much longer belt for obvious reasons.
The “squeeze” assembly did not use the current tensioner and had a bracket with two idlers at each end and was located above the block mid-line. This looked like a bar-bell with pulleys or as one side of a roller skate.

Tooth engagement:
This is determined by the valve-train hardware. If the hardware is stock, the returns of increased belt-wrap are greater. Likewise, the return of added belt-wrap on modified valve hardware is reduced.

Design changes/issues:
There were many things that were known risks. With the T-III, it started as a complete engine that Lotus had prepared and eventually ending up with what we have today. That is a substantial deviation from what was intended. Unfortunately, the valve train hardware was developed for their higher revving engine and was never revisited after there engine concept was thrifted, due to cost and complexity.

Gears and shaft wear:
Much of this can be answered with “yes”. Tension and speed aggravate the front intermediate shaft bearing while speed and the increased pump gear resistance causes the gulling that fails the gears. The TSB shaft and pump addressed the dissimilar gear surface issues but failed to address the root cause - The design was a bad idea and pushed the assembly beyond its limit.

Thanks and I hope this helps.

[TurboRon25]

I really think it more to do with belt tension. Every failure I have personally dealt with(not my own) has proven to be way too loose of a belt. I checked a few of them with the gauge before I pulled them apart and two of them were right at 45LBS. I was almost thinking that there is a certain number that causes just the right harmonics to cause the failure. Almost like how a certain frequecy will break glass I think its the same concept here. I have even seen a few pumps break off at the mounting flange instead of sheering teeth.

I've never owned or worked on a TIII so I maybe way off base. Anyway.

Is it possible that the I-shaft bearings wore enough to cause the belt tension to drop to 45LBS?

It's like the chicken and the egg, right?

Ron

btw. great thread!

[turbovanman²]

I've never owned or worked on a TIII so I maybe way off base. Anyway.

Is it possible that the I-shaft bearings wore enough to cause the belt tension to drop to 45LBS?

It's like the chicken and the egg, right?

Ron

btw. great thread!

Nah, that would be a ton of slop and things would get messy fast.

[iTurbo]

What kind of wear are you guys seeing on the I-shaft bearing? All the messed up ones I see are cracked with large chips missing.

[tsiconquest88]

i will full in with my failure details tomorrow morning when i drop the pan/pump. (have a post in the help section on this ordeal). 495 miles and mine lost oil pressure this afternoon. BTW jackson i seen you post the first 3 numbers in that warranty p/n thing, do you know the rest? i wouldnt mind finding that kit. Just seen one on ebay a few days back but it was missing the I-shaft and pump, as the guy said he used them, but through an a new oem pump lol. No i-shaft still though he said, but included some other parts the kit has. Something around 4 or 5 or so, parts.

[Lotashelbys]

What kind of wear are you guys seeing on the I-shaft bearing? All the messed up ones I see are cracked with large chips missing.

That sounds about right. EVERY TIII I have ever had apart with the factory bearings in it still looked this way.

[Simsy]

That sounds about right. EVERY TIII I have ever had apart with the factory bearings in it still looked this way.

not the two i had apart

[turbovanman²]

i will full in with my failure details tomorrow morning when i drop the pan/pump. (have a post in the help section on this ordeal). 495 miles and mine lost oil pressure this afternoon. BTW jackson i seen you post the first 3 numbers in that warranty p/n thing, do you know the rest? i wouldnt mind finding that kit. Just seen one on ebay a few days back but it was missing the I-shaft and pump, as the guy said he used them, but through an a new oem pump lol. No i-shaft still though he said, but included some other parts the kit has. Something around 4 or 5 or so, parts.

Just use an 8 valve int shaft, stock oil pump that's in good shape.

[tsiconquest88]

well i was thinking of getting the cryo shaft from fwd. I was trying to find that warranty recall kit which has the i-shaft, pump and some other pieces. But the chrysler p/n C3940462 from the moores mopar site isnt matching to anything when i google, the moores mopar site even has the whole bulletin on the site and how to do the recall and all still listed under spirit r/t tab. But i guess that kit isnt available anymore, it came from the national depot's i found out, and i went to their main site and left an email about it and see what they can come up with. Jackson mentioned a p/n for the recall parts under a 466 but cant remember the rest of it. Maybe thats the same kit but changed to the 466 numbers after a while.