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Discussion Starter #1
All,

Narrowed down a 408 stroker kit and think I want to put a 4R70W transmission behind it but don't know what flexplate to get. I have a 164 tooth stock flexplate now that was on the original engine. Should I just get a 164 tooth flexplate that they tend to offer on a lot of the kits? Tried a google search but can't seem to narrow it down.

Brian
 

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Use whatever the stroker kit vendor recommends - for two reasons. First, they should be able to help you with the 157/164 tooth choice. Secondly, they will tell you what the balance will be on the new engine - some are internally balanced and take a zero-added weight flexplate, and others will either use a 28oz or 50oz.
 

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Discussion Starter #3
Thanks Cougrrcj...I guess the reason I've asked is because the place I'm contemplating getting the 408 kit didn't want to guess as to what flexplate to sell us because he didn't know. I figured that the torque converter was the determining factor in what flexplate to use. I want to use a stock coverter as this will only be street driven in traffic. I also figured that the 164 tooth flexplate was what to use since it's what came on my car. Are the flexplate mounting patterns for the converter different on various flexplates or are they all the same? Sorry for the question but I'm green on automatic trannys!
 

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4R70W converters come in both stock- and high-stall factory versions. Crown Vic Sport and Police, as well as Marauder used the high-stall version. Stock is ~1700rpm, high-stall is around 2400. Since the 4R70W trans has an electronic lockup of the converter in D and OD, gas mileage will not be adversely affected with the high-stall converter.

With an overdrive trans of almost any sort, you can run a steeper rear end gear and still maintain low-rpm cruising down the highway. With 3.55 rear gears and a 27.3" tire, my engine is turning around 1800rpm at 60mph in OD.

You'll still need to know what imbalance the engine kit is balanced in order to get the right flexplate!
 

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Discussion Starter #5
Cougrrcj,

Makes sense. I suppose if I tell the 408 supplier that I'm going to run a 4R70W with a stock torque converter he should be able to tell me what flexplate is needed as I believe he uses the 28oz way of balancing and not the 50oz. Thanks!

Brian
 

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Discussion Starter #6
Ok guys,

Got a message back from the 408 supplier. He needs to know the following information: "For the flex plate I will need to know what torque converter you will use and what bolt pattern it will have."

I plan on running the 4r70w tranny with a stock torque converter. Does anybody know what the pattern is for that particular tranny? Looks like I need to supply him with that info so he can get me the right flex plate.

Cheers,

Brian
 

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If you tell him 'stock' he should know!
 

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Discussion Starter #8
Thanks Cougrrcj,

That is what I thought. Maybe he was thinking we were gonna run a different conv with different stall or something.

Brian
 
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