Turbo Dodge Forums banner

1 - 20 of 52 Posts

·
Registered
Joined
·
393 Posts
Discussion Starter #1
I've been playing around with different TIII Alternate Timing Belt routing installation to reduce timing belt slap and hopefully help reduce Oil pump failure. Just need a few parts and minor modification of AC compressor bracket. As you can see this mod does not cut out structural integrity of the AC bracket, but does require some metal removal to make sure you have clearance for the timing belt. This mod leaves the current idler pull in place. I'm using a smaller diameter idler pulley so it will have to work a little harder than the larger idler pulley. I still have to run the car around to see how it works at speed.

Alternate TIII belt routing.jpg

Ron
 

·
Registered
Joined
·
393 Posts
Discussion Starter #4
Idler pulley is off of a Subaru WRX STI 2.5 Turbo (227 hp and 236 lb-ft). I figured it was a similar application to our Dodge TIII 2.2 DOHC 225 hp at 6,000 rpm, 210 lb-ft at 4,800 rpm. I used a Gates P/N T41239 pulley. You will have to modify the pulley by grinding off center shaft to mount to the AC Compressor bracket.

parts needed.jpg

Ron
 

·
Registered
Joined
·
393 Posts
Discussion Starter #5
Does anybody know how to post movie clip ? Took quick movie clip this evening going from idle 900 RPM to 2500 RPM. You can see how this works

Ron
 

·
Registered
Joined
·
393 Posts
Discussion Starter #6
Update on alternate timing belt routing mod. After 50 miles various in town speeds and some highway speeds everything looks good.

Just a quick note, this is a TIII engine I just rebuilt from scratch. So I’m taking my time checking everything out during the engine break-in period. The initial startup had 30 miles on it. The Daytona R/T passed TX state emissions testing up the tail pipe without a hitch. A few days after the TX inspection the Melling oil pump gear went out and took out the intermediate shaft gear. Inspection of the new I shaft bearings that were installed in engine block looked good after the oil pump incident so I did not change out. Timing belt tension was 95 – 100 lbs with a new TBelt before and after the oil pump went out.

The fix, purchased Cryo I shaft from FWD (thanks Cindy for supporting these cars) and found new Chrysler oil pump. Reading the various forums on TIII oil pump failures and timing belt slack and tension needs I decided to try this mod. It took some time to find a small idler pulley that would work in the limited space on the AC bracket. It’s different from Jackson’s but really servers the same purpose to stabilize the timing belt slack issue. I’ll update the progress as I get more miles on the engine.

Ron
 

·
Registered
Joined
·
393 Posts
Discussion Starter #8
I'm leaving the original idler pulley in it's original position. This mod adds a smaller pulley onto the AC bracket.
 

·
Registered
Joined
·
393 Posts
Discussion Starter #10
I'm guessing you are talking about the main crank sprocket. This is the TIII sprocket normal configuration. It is made different than a 8 valve main crank sprocket.
 

·
Registered
Joined
·
36 Posts
Has there been any evidence that reducing slap will prevent I-shaft shenanigans? Though im not downplaying the fluctuations in torque it really seems like the majority of the issue is the much higher rpm.
 

·
Registered
Joined
·
331 Posts
Has there been any evidence that reducing slap will prevent I-shaft shenanigans? Though im not downplaying the fluctuations in torque it really seems like the majority of the issue is the much higher rpm.
Jackson and a couple other daily driven TIII's are pretty good arguments that this will solve the issue. Along with modified retainers.
 

·
Registered
Joined
·
393 Posts
Discussion Starter #15
Ron

It sure looks to me like you have the round tooth timing belt thats made in the UK on there. I would change it to the correct trapizoidal belt if that is the case...
Jackson,
You are right it is a round tooth. Brand new Clevite TB-206 made in UK written on Timing Belt. Still have box it came in, the box label say's in small letters (Not of Our Manufacture). That's just great.

OK, my guess the round tooth can slip a cog throw off timing? Would it have anything to do with original oil pump failure ?

Something else to write down and look for on the TIII engine. "Trapizoidal belt tooth/cog"

Back in the garage, dam I getting good a tearing this engine apart. I'll probably be able to set the timing in record time.

Thanks,

Ron
 

·
Holset Booster
Joined
·
3,535 Posts
Ron
Yes i would get a Gates T206 belt for it and make sure it says "Made in Italy" on the box and belt. That would be the correct tooth pitch. That was not the cause of your failure as much as tension I wouldnt think but that belt "matches" the teeth on the pulleys better.


One of the other ideas behind my original timing mod is for more belt wrap on the intake and I-shaft cam gears. Your idea does not quite give it as much and I think they need even more than running it my way. The other thing to keep an eye on is the speed that the smaller idler will be running. If its a "re-greaseable" bearing that you can pull the rubber seal out I would re-grease it every so often. I also dont think that the factory idler needs to be there right next to another idler(the tensioner) like many have argued with. The only reason for keeping it would be so that the factory lower timing cover fits un-modified. I dont mean any offence toward what you are trying if that looked like it came out that way.
 

·
Registered
Joined
·
3,447 Posts
Yea, umm, that definitely looks like the wrong belt. It definitely won't be happy like that.

Performing this timing belt routing modification provides two main benefits. One being that it makes the belt wrap around the cam gear more. Why this actually helps is still a mystery to me, but after just looking at most all other DOHC timing belt routing designs, they are doing this same thing.

And the other item, which I believe to be more important than pulley wrap, is that adding an idler in this area stops the belt flutter. I really think that this belt flutter that we all are aware of is what causes those oil pump gears to eat themselves. Consequently, a tighter belt means less flutter and will make those gears last longer. With the flutter, the oil pump drive gears are constantly hammering away at each other due to the constant and rapid rotational speed fluctuations that the intermediate shaft is experiencing, and gears do not like that.

The timing belts of the 8-valve engines will flutter in this same area with less trouble, but it could very well have something to do with the size of the intermidate shaft pulley (and resulting speed), valve spring pressure, and mass of the intermediate shaft sprockets in the T-III that creates a critical "flutter frequency" that kills them. Adding a pulley here alters this possibly-resonating flutter frequency to a point where things are safe.

Regardless of whether my theories hold any usable amounts of water, the fact doesn't change that it is proving to make things last substantially longer.

Also, it is not unheard of someone using an old chewed up intermediate shaft gear on a new oil pump. People do this with the distributor gears on their old school pushrod V-8's as well. "Wow. That distributor gear didn't last long! Let's stuff another distributor in there and see if the milk un-sours itself." This isn't the case all the time, but I'll bet vital parts of my anatomy to the fact that it is a contribution to the reputation of these engines over the years. I can't help but notice how some people eat up oil pump gear after oil pump gear and then someone like Jackson gets a hold of it, and the curse is broken. Coincidence?
 

·
Registered
Joined
·
393 Posts
Discussion Starter #18
Ron
Yes i would get a Gates T206 belt for it and make sure it says "Made in Italy" on the box and belt. That would be the correct tooth pitch. That was not the cause of your failure as much as tension I wouldnt think but that belt "matches" the teeth on the pulleys better.


One of the other ideas behind my original timing mod is for more belt wrap on the intake and I-shaft cam gears. Your idea does not quite give it as much and I think they need even more than running it my way. The other thing to keep an eye on is the speed that the smaller idler will be running. If its a "re-greaseable" bearing that you can pull the rubber seal out I would re-grease it every so often. I also dont think that the factory idler needs to be there right next to another idler(the tensioner) like many have argued with. The only reason for keeping it would be so that the factory lower timing cover fits un-modified. I dont mean any offence toward what you are trying if that looked like it came out that way.
Jackson,
No offense taken, this is just a new idea for an old problem. That’s what this forum is all about, ideas that keep the 2.2 DOHC cars running.

Original Chrysler Timing belt routing does have its quirks. I know when the engine is running you can usually see some belt slap or vibration in the timing belt from the intake cam sprocket to the oil pump sprocket. Probably the main reason a lot of people will over tighten the TIII timing belt in the first place is to reduce the belt slap or frequency VPS (vibrations per second).

I talked to a mechanical engineer about the belt slap and oil pump failures seen on the TIII cars and his suggestion was to change or reduce the belt vibration frequency VPS. This could be done by placing a idler pulley in the 11 inches belt path from the intake cam sprocket to the oil pump sprocket. The idea is to change the vibration frequency VPS versus stopping it.

With the large pulley up front I’d say you’re reducing if not eliminating belt slap. It probably moves some of the belt slap to the belt path between the timing belt tensioner and exhaust cam where it does not matter as much. The timing belt does cross the bolt head path that holds the power steering pump in place so you have to grind the bolt head to gain clearance for the timing belt path.

With the smaller idler pulley installed the belt vibration frequency is reduced and /or changed. With the engine off you can usually press your finger on the timing belt between the intake cam and oil pump and see the belt deflection. That’s all this mod does with minimal changes to the original design. Having the original large idler still installed with the smaller pulley should keep the timing belt tension more stable across its path while the engine is running.

The large pulley mod has been successfully installed in quite a few cars since you came up with the idea back in 2008. Probably using some of the same thought process as mentioned above. The smaller pulley is a new idea for the original oil pump problem; time will tell how well it works.

Ron
 
1 - 20 of 52 Posts
Top