Damper Size for 327

[Mitch]

Hi guys
I just sent my short block out to get redone. new rods ( scat), pistons .060 over racetec. small journal 327. ARP everywhere.
I had a 8in performance damper and the guy doing the work ( one of the best in the area) said the 6in is what he recommends.
He will of course rebalance the whole assembly.
I have read all sorts of threads on the subject but cant really find a definative answer.
this will be a street/ strip car. 4 speed. 4:71 gear.
any input?

 

[Grumpy]

Size It Up: Selecting The Properly Sized Balancer With Fluidampr

Getting the right sized harmonic balancer is more than just finding one that fits on the end of your crankshaft. We talked with Fluidampr to get some info on what you should look for in sizing a harmonic balancer.

www.dragzine.com

https://www.motortrend.com/how-to/hrdp-1009-6-or-8-inch-balancer-for-small-block-chevys/#:~:text=Low%2Dperformance%20327s%20tended%20to,of%20their%20relatively%20long%20stroke.

how dampers work

TAKE TIME TO READ THRU THESE A harmonic damper is a device fitted to the free (accessory drive) end of the crankshaft of an internal combustion engine to counter torsional and resonance vibrations from the crankshaft. This device must be an interference fit to the crankshaft in order to operate...

garage.grumpysperformance.com

ATI - Super Dampers® for Chevy Engines

ATI harmonic Super Dampers add horsepower and torque to race, street and truck engines.

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connecting rod & rod length too stroke info

I build mostly BBC engines, but most of this info also applies to SBC connecting rod selection, I was asked if stock rods were ok or should they swap to better ARP bolts or BUY the BETTER RODS WITH THE UPGRADED BOLTS, the first thing Id point out is that, in most cases, when I diagnose engine...

garage.grumpysperformance.com

for that application a STEEL 8" damper is your better option.
look at the specs a 8" steel damper counter weight on the 8" ati damper
,( LOOK AT THE LINK) it is about 4 times as massive as the damper weight on the 6 3/4" version
keep in mind as RPM's increase the inertial loads, on the rotating assembly very rapidly increase's.

Low-performance 327s tended to use the smaller 6 3/4-inch balancers, while the high-performance or Corvette motors (because they were driven aggressively and at higher rpm) used 8-inch balancers. Nearly all 350s came with an 8-inch balancer because of their relatively long stroke.

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it comes down to the LEVERAGE , or the level of inertia the damper can absorb then return, that energy to the crank in rotational inertia TORQUE
larger diameter dampers have a distinct advantage in both mass and leverage.

racing 302 engines and the 327 engines in the road racing corvettes all tended to use the 8" dampers
verify the timing tab TDC location matches the damper TDC location