Can someone ‘splain to me….

Daryl · Mar 20, 2024

I tapped on to an email from LMR, like I usually do, and started poking around the fuel injector page then the Drivetrain area. Here’s my questions:

1. How do you determine what lb injector to use? And which version with this? without that? Adapters or no?etc etc; and

2. Harmonic balancers: 26oz? 50oz? Which one? And why?

I know I have Accel 24lb injectors that Full Throttle Kustomz put in for me while the motor was being stroked. But WHY 24lb? And what do the weight differences on harmonic balancers mean? (or represent).

Even a Layman’s understanding would suffice for me. Always willing to learn… and not afraid or too embarrassed to admit my journeymanship!

Cheers and thanks everyone!

duh09 · Mar 20, 2024

Generally on injector sizing, you're going off of what power level that injector will support. There's a little bit of math you can do if you really want to dive in to figure injector size, but generally speaking the more lb/hr, the more power potential you can make. You want your injector to be in a happy duty cycle range for better efficiency in controlling fuel, so you won't oversize too far out, but a good tune can bring a oversized injector in line usually.

Here's a good little read on injector sizing: https://www.holley.com/blog/post/how_to_properly_size_fuel_injectors_for_your_engine/

The changes in body styles of injectors over the years are why you see so many variations in them. There's a height difference and a connector difference between the different styles, but they all do the same thing, adapters just allow the connection to plug up securely. You sometimes have to get creative to make sure the fuel rails are fully seated and held down with the longer injectors but it's not a major deal.

Harmonic balancers different oz are to match the imbalance in your crank. HO302s are 50oz, older motors are 28oz, you're matching whatever imbalance your crank is machined to. Stroker cranks can be built to whichever balance, some even have a 0oz neutral imbalance. The imbalance exists to cut down on on the vibrations created from the crank spinning.