Re: Harmonic balancer info

Posted by Anthony Pallett On 2014/4/8 1:39:07

David, I am by no means an expert on engine harmonics but from what I do understand the balancer must be reasonably matched to the operating RPM of the engine. One that is set up to work with the 2000-2500 RPM range of the post war L8 is likely fine for that range, in my build I am attempting to stretch that to 4000-4500 RPM if possible and I feel that the stock style balancer wont be up to the job.

In the V8 Chevy world they have 2 common balancers (6 inch and an 8 inch if memory serves) the 6 inch was generally fitted to the 327 and smaller engines which had a stronger stiffer (all other factors equal) crank due to more overlap between the rod and main journals in the casting/ forging thus creating a crank less prone to flex where as the 350 and 400 CI engines (though the 400 was externally balanced) had the larger balancer, less overlap of the main and rod journals more flex and vibration equals the need for a bigger/ heavier balancer.

In the L8 engines where you have a proportionately long stroke, IE my 327 has a longer stroke than a 427 Chevy it will be more prone to flex and vibration than say a shorter stroke 288 or a more modern oversquare engine (big bore short stroke). Drag racers tend to use the smallest balancer available myself included when I ran small block Chevy engines due to the reduced rotating mass (think lightened flywheel)they were able to rev faster thus getting you into your power band quicker during launch and as you went through the gears. In the L8 no matter what I do it will never be a quick revving engine in the modern sense so I am not as concerned with the rotating weight as I am keeping the potentially severally damaging harmonics at bay.

I am a racer at heart as many of you know and in the racing world any engine that was slightly warmed over from stock it was advised to use a more sophisticated balancer that a stock cast two piece unit with a rubber isolater between the two. Properly controlling engine harmonics will increase power and longevity in any engine out there.