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Thread: Center oil drain-back mod

  1. #1
    boostaholic
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    Center oil drain-back mod

    I just wanted to tell everyone about the next "trick" to make a TIII motor live long and prosper. This something I have been doing since this spring on about 5 or 6 engines now. What you do is drill the center oil drain-back hole in the TIII head just like what all the 8valve heads had from the factory. The only reason I see it not being done from the factory is to utilize that poor excuse for a PCV vent in the front of the block without oil blowing everywhere. The interesting thing is that center drain-back hole runs right down on the I-shaft right next to the teeth that so often like to strip off. I seen to think having oil poured on the teeth whenever the engine is running would really help things stay happier much like the 8valve and Masi shafts seem to be. Anyways here are a few pics that will be worth a 1000 words.

    Pic of a stock head that is not drilled. A circle is drawn where the hole would be using an 8valve head gasket. This will line up with the center drain thats in the block already....





    Here is a pic with the new hole drilled. I have been using a 7/16" bit to do this. the reason being is the little shelf on in the head that would be covering half the hole if it was drilled centered. I stay to the front edge of the drawn circle. You would of course drill the head gasket the same way as the head was drilled....




    Next is the new block drain that you will need. I drill and tap the center of the area that the dist hole would be on an 8valve block and make it a 3/8NPT. Then, install a 3/8-5/8" hose barb fitting....




    Rest of the pics and info on next post.......

  2. #2
    boostaholic
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    Re: Center oil drain-back mod

    Continued from first post since I keep getting forbidden message.....

    This is how the breather/separator setup will look now underneath the intake. I use about 7.5" of 5/8" silicone oil hose and make it arc right around the intake. You will have to either cap the old block vent or pull the fiting and install a frost plug there now......




    And last here I have a light shining through the center drain-back hole in the block to show right where it lines up with the I-shaft. I have pulled the B/S box off on a car with this done and looking in the factory block port could see a "waterfall" of oil running down this new hole with it just at idle. I can just about imagine how much better having all that oil running on the shaft teeth must be for things.



    I really cant see how doing this can hurt a TIII in anyway. I have this done on 2 of my cars I have driven alot this past summer and one was my 89 CSX that was run hard most of the summer including at the SDAC 24 event. What does everyone think???

  3. #3
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    Re: Center oil drain-back mod

    Quote Originally Posted by Lotashelbys View Post
    Continued from first post since I keep getting forbidden message.....

    This is how the breather/separator setup will look now underneath the intake. I use about 7.5" of 5/8" silicone oil hose and make it arc right around the intake. You will have to either cap the old block vent or pull the fiting and install a frost plug there now.....
    And last here I have a light shining through the center drain-back hole in the block to show right where it lines up with the I-shaft. I have pulled the B/S box off on a car with this done and looking in the factory block port could see a "waterfall" of oil running down this new hole with it just at idle. I can just about imagine how much better having all that oil running on the shaft teeth must be for things.
    I really cant see how doing this can hurt a TIII in anyway. I have this done on 2 of my cars I have driven alot this past summer and one was my 89 CSX that was run hard most of the summer including at the SDAC 24 event. What does everyone think???
    Jackson,
    I understand your effort here but please consider the speed in which the gears are rotating will centrifugally sling the oil from the top of the oil pump before it's ever allowed to penetrate the gear surfaces.
    Lubrication is not as much an issue while the gears are over-driven by the reduced T-III cam pulley size.
    A simple but effective sleeve will allow the T-III cam sprocket to be used on the intermediate shaft and therefore adequately support the cam belt width while reducing the shaft speed to the standard level.
    This considers the source of the issue and the fact that the gears are run too fast and the oil (centrifugally) has no opportunity to provide proper lubrication, even when splash fed by alternate means.
    Even the melonized gears provided through the dealership TSB system were a band-aid at best while the true issue was over-driven speeds.
    A proven consideration is the high volume (not high pressure) oil pump while running it at cam speed.

    I will post the adapter sleeve pics as soon as they become available.

  4. #4
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    Re: Center oil drain-back mod

    Ken
    I totally understand where you are coming form about the speed that the TIII shaft spins compared to 8valve. I have often thought about that and I have ran a machined out outer TIII exhaust can gear and an 8valve inner hub to run it an cam speed. The only thing I dont like is there is not enough timing belt now to run an idler on the front run between the intake cam and I-shaft. If we had a longer belt from some other application that would be a great modification. I was just thinking any other "splash oil" from the center drain would help for lubrication on the teeth. I would think some oil being ran on top of the teeth would be better than almost none at all like how the factory setup is. Even if nothing is gained here I cant see how it could cause any harm to the engines I have already done this to.

    For the record,I have seen at least 5 of the TSB "melonized" shafts have enough wear on the teeth that I would not want to run them again.

  5. #5
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    Re: Center oil drain-back mod

    Quote Originally Posted by Lotashelbys View Post
    Ken
    I totally understand where you are coming form about the speed that the TIII shaft spins compared to 8valve. I have often thought about that and I have ran a machined out outer TIII exhaust can gear and an 8valve inner hub to run it an cam speed. The only thing I dont like is there is not enough timing belt now to run an idler on the front run between the intake cam and I-shaft. If we had a longer belt from some other application that would be a great modification. I was just thinking any other "splash oil" from the center drain would help for lubrication on the teeth. I would think some oil being ran on top of the teeth would be better than almost none at all like how the factory setup is. Even if nothing is gained here I cant see how it could cause any harm to the engines I have already done this to.

    For the record,I have seen at least 5 of the TSB "melonized" shafts have enough wear on the teeth that I would not want to run them again.
    I also get what your trying to do - give it something more than it currently gets!
    Possibly an inner baffle or gutter (much like the 5th gear gutter in the manual trans) that can deliver the oil to the meshing point rather than being slung from the top of the oil pump could be very effective.
    In addition to any oil delivery method that concentrates the oil at the mesh point rather than the top of the oil pump, is "gear indexing" during the engine assembly process.
    Have you ever done this?.. It works !

    After failing a shaft and/or gear or two myself - I started looking very closely at the two gears and realized that several of the oil pump gears I tested were non-concentric along with the intermediate shaft counter-part.
    It only takes .002-.003" of run-out on each shaft to realize a variation in rotating torque, especially when the peaks of each align within rotation and produce a minor level of bind.
    After insuring that the rotating torque is constant throughout 360 degrees of rotation, I have not failed a gear set since.

    BTW
    The T-III adapter I had machined cost $25 to complete.
    I need to pull the pulley off of one of my recent engines to take a pic but it basically looks like this with a notch for the key.
    It's simply there to take up the difference in ID vs OD and center the pulley - tighten the bolt and it just goes along for the ride.
    Have you considered using a modified T-II tensioner to give you additional belt for the front idler while using a T-III intermediate pulley?
    Just a thought - don't know if it'll give you the belt slack you need for the larger pulley.



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  6. #6
    Supporting Member II Turbo Mopar Contributor DOHCRT's Avatar
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    Re: Center oil drain-back mod

    Ken, What are your thoughts on Warren's gun drilled intermediate shaft that directly oils the gears while meshed. See Post #100

    http://www.turbo-mopar.com/forums/sh...ing-back/page3


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    Re: Center oil drain-back mod

    Quote Originally Posted by DOHCRT View Post
    Ken, What are your thoughts on Warren's gun drilled intermediate shaft that directly oils the gears while meshed. See Post #100
    http://www.turbo-mopar.com/forums/sh...ing-back/page3
    I like that - it delivers the oil to the critical meshing area.
    The hole diameter specified shouldn't suffer this but has there been any occurrences of debris blockage?
    Are the gear holes offset to minimize stress risers?

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