A very well balanced engine will keep on spinning up. A Engine not well balanced will come apart quickly.
416, Indy 360-1 heads. 686 roller. 2" tubes. 12.5-1. Heavy steel crank and rods. 829@7900. Best times were achieved a 8000 shift. Shift light set at 7800. Car was heavy. @ 3850 with 200 lb. driver.
You can tell the difference on a solid mount run stand when they are Balanced within 2 grams they are Very smooth. Harmonics will kill an engine.
The last Low mileage stock 340 on the stand you could feel was not balanced. That is the way some were. If your engine is is solid mounted in the car and you can feel it in the chassis holding it a 4000 just shift it where it can handle it. Like I said bad harmonics is what kills engines. Balancing is critical. After starting so many engines you can feel the few built by others that were not balanced.
