On a 455 making under 500HP, how reliable/safe are the stock OEM style Flexplate & Harmonic Balancer?

 

I see no issues with using stock.

 

Stock flexplate that doesn’t have sloppy holes for the converter or flexplate to crank flange can hold a decent amount of power, probably close to 500hp, if the balance weight is welded on well and it doesn’t get a stress crack.

The stock or rebuilt factory dampers are the most likely things to fail at higher HP /higher RPM with the outer ring spinning or moving on the elastomer isolator.

I have bought rebuilt stock balancers and seen the rings slip several degrees when checking timing and comparing true TDC on less than 400hp 455’s.

ATI and BHJ make great dampers for our Olds engines.... reliable, rebuildable, and effective with true SFI sticker

I went with a Speedmaster 79 Billet Flexplate with bolt on external weight and it was a nice piece and SFI approved also.


buy once, cry once

 

The balancer is not a item you want to try and save money on. Go cheap on the valve covers and air cleaner. When I'm checking total advance ignition timing, I do not want to be struck by shrapnel from an exploding balancer.

 

ATI also makes an Olds-dedicated flexplate, SFI approved 166 tooth. Have one on behind my 350 and it's a stout piece - I believe p/n = ATI915565

 

I'm appx 420 ish HP with my sbo. Stock balancer and flex plate spun to 7k rpm

 

Your block will give up before flexplate and balancer.