Max rpm for valvetrain?

[DMotorsports]

I know the limiting factor in the stock engine seems to be the rods. I was just wondering with a built short block what rpm are the heads (namely, the valve springs) good for?

 

[Robertt305]

I been pushing my KB car to 65-6600 no problems with 700rwhp

 

[F8L SN8K]

The valve springs are ok till 7,200 before losing control. The roller figure followers are stable until 8,000rpm(John and mike at MP ran stockers to 9+ but also was pulling covers to check and sometimes re-install the ones that popped off on the 4.6 after every run) . Stock head flow will not support that cfm and the stock oil pump gears will be an issue at those harmonic frequency. Mind you at 7,200 rpm you have mean piston speed the same has an F1 car at 19,000rpm(5,000 ft per minute). A 5.4 at 9,100 rpm mean piston speed is the same as Prostock in NHRA(10,000 rpm 6,300fpm). And at 9,800 rpm(6,800fpm) you are actually "out running" the flame front and reducing BMEP(effective pressure).

Remember none of that really matters if you don't have the head flow and proper cam duration to support the required air supply to fill the cylinder. You can only draw in or force in so much air through an opening before it starts to take more energy to fill the cylinder then the extra amount produces. Diminishing returns.

 

[DMotorsports]

The valve springs are ok till 7,200 before losing control. The roller figure followers are stable until 8,000rpm(John and mike at MP ran stockers to 9+ but also was pulling covers to check and sometimes re-install the ones that popped off on the 4.6 after every run) . Stock head flow will not support that cfm and the stock oil pump gears will be an issue at those harmonic frequency. Mind you at 7,200 rpm you have mean piston speed the same has an F1 car at 19,000rpm(5,000 ft per second). A 5.4 at 9,100 rpm mean piston speed is the same as Prostock in NHRA(10,000 rpm 6,300fps). And at 9,800 rpm(6,800) you are actually "out running" the flame front and reducing BMEP(effective pressure).

Remember none of that really matters if you don't have the head flow and proper cam duration to support the required air supply to fill the cylinder. You can only draw in or force in so much air through an opening before it starts to take more energy to fill the cylinder then the extra amount produces. Diminishing returns.

Great info. Thanks. :beer:

 

[na svt]

I've used stock oil pump housings and GT lash adjusters/followers on 8500rpm engines. I know of two NMCA engines spinning 9000rpms with GT adjusters/followers. John's NMCA engine runs a stock type pump, 4.0 followers and stock (non-GT followers).

With boost the heads are not a restriction, not even close.