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4r70w flexplate?

Cobra11

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Full Member
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Jun 28, 2008
Messages
520
Loc.
West Hollywood, CA
just looking for thoughts and opinions for what type of flexplate i should spring for. i know i need a 28oz 164 tooth...but i was looking at summit and they have what looks like a bottom dollar or stock type for about $50. then it jumps to about $125-200! there's nothing in between, so im wondering if need to spend the extra money or not. i know i def don't want to cheap out and pay for it later though!! thanks guys

btw...its going on a remanufactured 351w.

also, does it matter if its 28oz or 28.2oz and external or internally balanced?

http://www.summitracing.com/search/...alance/External-28-oz-imbalance/?Ns=Price|Asc

just thought i'd throw in a pic of my new motor!!
 

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Broncobowsher

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Joined
Jun 4, 2002
Messages
35,673
It looks like just about any of those will do.
No difference between 28 and 28.2 for the balance. Just a matter of if they print the decimel point or not.
You want the non-C6 version

I ran a rockauto search and found ATP Z105 and Dorman 04352 as other part numbers for stock replacment.
 
OP
OP
C

Cobra11

Contributor
Full Member
Joined
Jun 28, 2008
Messages
520
Loc.
West Hollywood, CA
It looks like just about any of those will do.
No difference between 28 and 28.2 for the balance. Just a matter of if they print the decimel point or not.
You want the non-C6 version

I ran a rockauto search and found ATP Z105 and Dorman 04352 as other part numbers for stock replacment.

does it matter where its balanced though? internal or external
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
35,673
Any time an oz-in (imbalance factor) is listed for a flywheel, flexplate or damper it is externally balanced. It isn't that the (pick one, I call flywheel) flywheel cares if the inbalance comes from adding weight on one side or if metal is removed from the other. What it is actually refering to is the crankshaft. An internally balanced engine has 100% of the counterweighting done in the crankshaft. Externally balanced engines don't have all of the counterbalancing internally, a small portion of the counterbalancing is done external to the crankshaft. That final balancing is the external balance.

As for the number itself. OZ-IN is ounces of weight multiplied by inches of radius. So 28 ounces at 1 inch from the crankshaft centerline would be the same as 14 ounces 2 inches away. 7 ounces at 4 inches, even half an ounce at 54 inches is all the same.

The $50 parts are stock replacment which are fine for a stock engine
The $200 are race parts that carry certification stickers that say the part won't blow up when racing. Not needed and can actually cause other issues. Sometimes they are thicker and don't flex as well as a stock replacment which puts a lot more force on the thrust bearing on the crank.
I did the $70 B&M flexplate for my warmed up 351 (11:1 compression, aluminum heads, etc.). A stock replacment should be fine for you. It would have been fine for me as well. I ran a stock flexplate on the 330" stroker 5.0 I built up for the Ranger and it was a lot more RPM happy then the 351 was.
 
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