after searching i'm still not sure. is a stock lt1 flex plate neutral balanced?
thanks

 

Yep...

The LT-1 is internally balanced so you have a neutral balanced flex plate.

You use a counter-balanced flexplate/flywheel on an engine that is externally balanced due to long stroke / big piston/rod combo, such as a 400 small block or a 454/502 cid (or bigger) Big Block when you don't have enough room in the block for a large enough counterweight on the crank to offset the rod/piston/throw weight.

-Dave C. '97 Z28

 

Actually, GM made the move to externally balanced flexplates in '86 on the small blocks...the same year they began installing the 1 piece rear main seals. The LT1 is externally balanced.
Kevin

 

Then which flexplate would be the best flexplate for the LT1?

 

I think I'm pretty much the subject mattter expert here as I have done EXTENSIVE reserch on this with my stroker rebuild. Don't believe me, do a search and you'll see me asking a million questions on this First, as bad79z28 said they are externally balanced, or have weight added to them. If you're running stock sized internals then any SFI approved replacement flexplate would be a good choice. You only need a neutrally balanced flexplate if you internally balance your motor, like perhaps with a stroker. And the ONLY one I have found is the ATI one. If you want the part # and where to get it just let me know. Hope that helped.

 

But the LT1 doesnt have a standard flet plate bolt pattern for the crank. the bolt pattern is smaller than most 350's (due to the one piece rear main seal)

Which flexplate (specifically) will work for the LT1? THank you.

 

Very true. I would imagine that if you bought any replacement LT1 flexplate you'd be just fine. There's a particular part number for the LT1 specific stock flexplate, so those are not hard to find. It's when you're trying to get a neutral one that it becomes a pain. Anyway, I know that Advance Auto sells a heavy duty version as well.

 

okay, the engine is a stroker and the build sheet specifically says internally balanced must use neutral balanced flex plate. so you say the stocker is not and ati is the only one making one? could use a part# if you don't mind.
thanks

 

I've called DOZENS of places and ATI is the only place I know that makes/has them. Besides, it's a quality piece too. The part number is 915533. My advice is to call ATI directly to get it. Summit and others has them but they are on backorder and are like 30-40 dollars more. They told me that they don't usually sell to individuals but just tell them that you really need it and that everywhere else is on back order. They sold it to me for $160 which is $35 less than summit. Hope that helps.

 

thanks for the info.
seems kinda strange with all the lt1's running around it's that hard to find one

 

I was thinking the same thing when nobody was able to help me out. I know there are some people out there that simply remove the weight from the stock piece, but I really wasn't comfortable with that as it wouldn't ever truly be made neutral when you take into account the welds, etc. Anyway, glad that all my work paid off for me and someone else. Good luck on your project.