6 replies to this topic

[mariner]

 A nice video of a 5.7 litre two valve per cylinder pushrod small block Chevy running up to 11,000 rpm.

 

https://www.enginela...-rpm-dyno-pull/

 

The builder admits that peak power is down at 9,000 rpm but it can reach 11K under its own power.

 

Maybe we should put videos like this a soundtrack archive to remember the noise when all cars, road or racing, are electric!

[Bikr7549]

Wasn't the DFV only limited to this (by regulation) in the first F3000 series?

[sblick]

I have talked to dyno techs at Roush who would think 11,000 rpm is not much.  If rumor is true NASCAR motors, before the RPM/Speed restrictions, were doing 14k RPM.  The tech I talked to said it idled at 7, and warmed up at 9.  Go back to old restrictor plate races and listen to them wind out.  I would say 2004-2006 era IIRC.

I would admit 11k for a street build is impressive

[Fat Boy]

A flat crank V-8 has a nasty harmonic about 96-9700 RPM, I believe. I ran a Judd in an LMP675 car quite a while ago, and it was an issue. You either had to do with the lower revs or be prepared to operate significantly above it. It would break the bolts in the clutch basket from the vibration. The present LMP2 engine only turns 8900 for a similar reason.

[Charlieman]

In the early days, DFV rev limits were defined by vibration in the valve gear train. The problem was resolved in the early 1970s for F1 cars and the DFV became a possibility (at lower than F1 revs) as a sports car engine. 

[Bikr7549]

Came across an interesting DFV article on running it in vintage races.

 

https://primotipo.co...ry/restoration/

 

His comments on operating it are:

• 11,000 rpm limit = 3 to 4 hours of run time and a $10-15k repair bill (2011)-this was probably how they were run in competition (maybe a race and then few practice sessions?)
• 10,000 rpm limit = 1000 miles of use before overhaul needed
• running it on a dyno he had a dyno driveshaft failure at 9200 rpm-just about the speed that FB mentions as being a problem with flat crank engines

Edited by Bikr7549, 26 November 2019 - 03:11.

[Charlieman]

I looked up a report of DFV practice for 1967 when the engine was first raced. Primary vibrations set in at 8,600 rpm but could be driven through. Secondary vibrations arose at 9.600 rpm. Lotus operated a rev limit of 9,500 rpm while Cosworth worked on mitigations.