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My name is Marc Duclos I'm just try to get a straight answer on what flex plate i must use. I would like to first say I am 46 yrs old and i always had 400 turbo tyrannies. I'm a truck guy. and i have a project that has to get finished. I have a 1986 Chevy four Dore dull 4x4 . And I just had the 400 rebuilt and i bought a ht 383 from crate depot. I never really understood why crate sent me the engine with a 12" flex plate with a weight on it. My sails men told me he could get me the 14" one for my set up. The question is My sails men said to prevent a vibration the crate ht 383 is balanced by the 12" flex plate. and because it has a one piece rear Maine. And he said not to put a after market on this engine. The tranny shop that did the work installed 99-761 and I matched it up with 14088761 under gm parts. I may seem to be a warrior but if the 12" is for external balancing then dose the 761 flex plate do the same thing for us or do we have the wrong flex plate. I got two Traney shops that I use and one is out to lunch and the other got my truck in September and i towed it back to my finishing garage last week march 5Th. I gave the trany guy plenty of time but now we need the truck. I need to no if a 400 turbo fully rebuilt with a empty torque converter should be filled with the carte ht 383 engine running for the first time with the 14" flex plate #14088761. I'm ready to take the trany out and do it my self like I alway do but before I get ahead of my self do you have any suggestion.
 

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Stroked Z28
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I'm not sure I completely follow you, so here is what I understand:

1. You have an externally balanced 383 Engine that came with an externally balanced flex plate. This engine: http://www.gmhorsepower.com/HT_383.html see installation note - external balance...

2. You are asking if the equivalent 14088761 flexplate will work on that engine. This is the flexplate: http://store.summitracing.com/partdetail.asp?part=NAL-14088761&autoview=sku

If that is indeed your question, the answer is NO. While I'm not a slush box guy, it should be safe to say that a flexplate for an internally balanced engine should not be used on an externally balanced engine. Put the HT 383's original flexplate back on the engine and get the appropriate torque converter. I'm not sure if your old starter will still work or not...

If I'm missing something here guys, please chime in...
 

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marc duclos said:
My name is Marc Duclos I'm just try to get a straight answer on what flex plate i must use. I would like to first say I am 46 yrs old and i always had 400 turbo tyrannies. I'm a truck guy and i have a project that has to get finished.

I have a 1986 Chevy four Dore dull 4x4 . And I just had the 400 rebuilt and i bought a ht 383 from crate depot. I never really understood why crate sent me the engine with a 12" flex plate with a weight on it. My sails men told me he could get me the 14" one for my set up.

The question is My sails men said to prevent a vibration the crate ht 383 is balanced by the 12" flex plate. and because it has a one piece rear Maine. And he said not to put a after market on this engine. The tranny shop that did the work installed 99-761 and I matched it up with 14088761 under gm parts. I may seem to be a warrior but if the 12" is for external balancing then dose the 761 flex plate do the same thing for us or do we have the wrong flex plate.

I got two Traney shops that I use and one is out to lunch and the other got my truck in September and i towed it back to my finishing garage last week march 5Th. I gave the trany guy plenty of time but now we need the truck.

I need to no if a 400 turbo fully rebuilt with a empty torque converter should be filled with the carte ht 383 engine running for the first time with the 14" flex plate #14088761.


I'm ready to take the trany out and do it my self like I alway do but before I get ahead of my self do you have any suggestion.
You have to use the external balance flywheel that GM bolted on the 383 crate engine.

The large diameter 13.5" converter for the t-400 will not bolt to the small flywheel ( as I recall) .... the smaller diameter converter typically used in small block applications 12" converter will bolt on.

The trans must have oil in it if you are running the eninge and the converter is bolted up.
 
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