489 BBC internal balance harmonic balancer?

[urbex]

I'm building a 489 BBC with a Scat stroker crank. I ordered the rotating assembly to be internally balanced. I know the 454 balancer and flex plate won't work now because they're externally balanced. I also know that the 396/427 BBC is internally balamced. Can I run a factory style 396/427 balancer on the 489 crank, or do I need to step up to something like an aftermarket ATI balancer now?

It's a budget build kit, utilizing one of the lower end Scat rotating assembly kits. I don't recall the part number off the top of my head...basic cast crank, forged rods and pistons. It was supposed to just be a basic refresh on the 454 stuff, but after dropping and bending a piston, I found the stroker kit to only be a few hundred more than the basic 454 rotating assembly, so I figured why not, lol.

It's going to be a double duty street and light trail truck, it will never see racing duty, and I don't intend to spin it any faster than 5500...more than likely will never go past 5000rpm.

 

[Bent77]

Personally I’d spring for an aftermarket one. Typically the factory balancers have enough wear that they can be a liability more than a cost saving method

@folkenheath May have some good input

 

[urbex]

Factory "style", not an actual 40 year old factory unit.

 

[folkenheath]

I used a factory one on my 489 ten years ago and had a factory one on my 388 for 20 years, the SB one was used when I installed it. I think if you are keeping it at 5-6k or under it should be fine. I would trust a GM unit (new or good used) over a chinese piece. You can feel the quality difference and the material is critical when spinning at RPM. I don't trust the imported stuff on that.

What I do recommend is to use a razor blade to shave off the access elastomer to make sure everything is flush and square on the front surface. Then take a paint marker to put a line on the front of it from the inside hub across the elastomer over to the outside ring. Then if it ever moves you can see it, if it ever moves it needs to be replaced. A new GMPP 427 balancer is not that expensive.

I do use an ATI super damper on anything that's over 6k RPM, there are a lot of gimmicks out there, that one is simple, effective, and rebuildable. Also, I typically upgrade to an SFI flexplate over 5500 RPM, just because the consequences can likely be more severe if it seperates, as your feet/toes won't win that battle and they are pretty inexpensive usually, I get the Pioneer brand (USA made) for low HP stuff(under 6500 ~600hp), and upgrade to ATI for the higher power high RPM stuff.

 

[urbex]

Cool, thanks. I just couldn't find any good info on whether the 396/427 units would physically fit/function on the 454/489 crank snouts, and I don't have anything here but 454 cranks to measure/compare to.

 

[folkenheath]

Cool, thanks. I just couldn't find any good info on whether the 396/427 units would physically fit/function on the 454/489 crank snouts, and I don't have anything here but 454 cranks to measure/compare to.

Yes it will. Although many aftermarket units have to be honed to fit so you don't snap off the install tool. They make them tight on purpose so they can be fit to the crank.

 

[AJs72K5]

Yes it will. Although many aftermarket units have to be honed to fit so you don't snap off the install tool. They make them tight on purpose so they can be fit to the crank.

I learned this one the hard way. Broke the install tool when putting on my ATI balancer the first time.