High Engine RPM Weakest Link

[Born30YrsLate]

Got a question for you engine builders out there. What is the weakest link when building a high rpm big block...let's say 7000rpm range. My initial thought was the stroke, but I was told by another person that it was bore diameter because the larger the bore diameter the lower the natural frequency. I really don't want to go through all the calculations of shear stress and strain or for determining natural frequencies so I thought someone has to have lived it or have some working knowledge of this subject.

[Salvatore]

I would say the valve train may be the weakest part.

[larry_csa]

I would have to say rods. The bigger the bore the heaver the piston the more stress on the rods. 396s are turning 8,000 to 8,500 427 are in the high 7s. I have a L-88 coming off the Dyno this week or next and I'll let you know the HP range

[3macs1]

I'm with Sam. Any big block we destroyed racing usually valve train started the distruction. Years ago stock engines were known for dropping valves.

[larry_csa]

10 deg valve locks and good valve springs will stop that. Valve flutter is what drops valves

[3macs1]

Agree 100%. I was referring to stock BBC. They ate valves.It was rare to see a rod failure come back to the shop unless stock bolts were used in the rods. Oil pump pick ups cost a lot of high rpm engines as did the plastic coupler on the pump drive shaft.That was years ago however not up on it today.