TF727, offset dowel pins...
#1342174
11/27/12 01:33 PM
11/27/12 01:33 PM
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Joined: Dec 2010
Posts: 208 Norrland, Sweden
Swedcharger67
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Hi all, I'm doing a complete overhaul of both engine and the 727. The 727 is totally worn out in all bushings and the thrust washer between input and output shafts is in a really bad condition. I see that offset dowel pins, for accurately lining up the engine with the auto, are available from several wellknown sources. How can I predict what offset I need, and can I measure it somehow?? Cheers, Martin
Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection
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Re: TF727, offset dowel pins...
[Re: Swedcharger67]
#1342175
11/27/12 03:54 PM
11/27/12 03:54 PM
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Joined: Jan 2003
Posts: 25,967 Rio Linda, CA
John_Kunkel
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The only way to know for sure is to bolt the actual (empty) case that you're going to use to the block and dial it like you would a standard bellhousing using the pump housing bore.
Case alignment would affect some of the bushings but if all the bushings are bad I wouldn't suspect case alignment....probably lack of lube.
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Re: TF727, offset dowel pins...
[Re: Swedcharger67]
#1342178
11/27/12 08:04 PM
11/27/12 08:04 PM
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Posts: 25,967 Rio Linda, CA
John_Kunkel
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The year of the case is irrelevant, all 727 cases are (supposed to be) machined to the same center relative to the dowels.
Gross misalignment is due to accumulated tolerances, i.e. dowel holes to the extreme tolerance in one direction and the the crank bore to the extreme tolerance in the opposite direction. Doesn't happen that often and usually results in cracked flex plates.
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Re: TF727, offset dowel pins...
[Re: John_Kunkel]
#1342179
11/28/12 07:03 AM
11/28/12 07:03 AM
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Joined: Dec 2010
Posts: 208 Norrland, Sweden
Swedcharger67
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Yes, I don't expect a big problem here. But I'm spending a lot of money on both engine and trans, it would be a pity not to make sure that they mate together perfectly. A perfect aligment will probably be good for longevity, smooth running, and it would make me feel good!
Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection
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Re: TF727, offset dowel pins...
[Re: Swedcharger67]
#1342182
11/29/12 03:38 PM
11/29/12 03:38 PM
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Joined: Jan 2003
Posts: 25,967 Rio Linda, CA
John_Kunkel
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If you intend to dial in an auto trans case the question becomes what do you use for a tolerance for runout. Auto trans will forgive more misalignment than a standard trans due to the auto trans' flexplate.
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Re: TF727, offset dowel pins...
[Re: John_Kunkel]
#1342185
11/30/12 04:06 PM
11/30/12 04:06 PM
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Joined: Dec 2010
Posts: 208 Norrland, Sweden
Swedcharger67
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Quote:
So if it's .002" out you're gonna correct it?
I will certainly do my best to, if possible, eliminate all misalignment. If I have done the best I can then that's ok with me. With all internals and bearings/bushings new in engine and trans, and a "stiffer" flexplate to handle the significantly increased engine output, I think this issue has become important and I will do whatever it takes to get it right.
Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection
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Re: TF727, offset dowel pins...
[Re: Swedcharger67]
#1342186
11/30/12 08:17 PM
11/30/12 08:17 PM
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Joined: Jan 2003
Posts: 25,967 Rio Linda, CA
John_Kunkel
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So, your goal is zero misalignment?
Let's take a practical look at that; suppose you dial the case dead nuts center but the center hole in the pump housing is off center to the right the maximum allowable tolerance and the input shaft support is off center the maximum allowable tolerance also to the right. Then suppose your case was offset to the right but you corrected it to center....what you have done is taken a set of tolerances that resulted in perfection and made them imperfect.
My point? Mass production doesn't make for perfect parts, they have a deviation tolerance and those tolerances can work for you or against you. Bottom line, leave it alone...you're overthinking it.
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Re: TF727, offset dowel pins...
[Re: John_Kunkel]
#1342187
12/01/12 10:12 AM
12/01/12 10:12 AM
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Joined: Dec 2010
Posts: 208 Norrland, Sweden
Swedcharger67
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I see it this way: Everything has manufacturing tolerance + or -. In this case we have: 1. the position of the crank in the block 2. the position of the dowel pins in the block 3. the position of the dowel pins in the bellhousing 4. the position of the pump bore in the bellhousing 5. the position of the center in the pump housing.
If I line up the crank with the bellhousing pump bore, with little or no misaligment, I have cancelled out all the manufacturing tolerances 1-4, no matter what they are. What I have left is number 5, the position of the center in the pump housing. Since I guess the outer perimeter of the pump housing is getting finished in a lathe with the center hole as the reference, and I must assume this is pretty accurate and centered.
I cannot see any other conclusion than that the alignment efforts are well worth doing?
Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection
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Re: TF727, offset dowel pins...
[Re: Swedcharger67]
#1342188
12/01/12 04:12 PM
12/01/12 04:12 PM
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Joined: Jan 2003
Posts: 25,967 Rio Linda, CA
John_Kunkel
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#5 assumption is iffy and you forgot #6 the center of the reaction shaft support.
Worth doing? An exercise in futility IMHO but have at it.
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