RPM limiting on a Performance Rebuild...

As engine rpm increases, the bleed down rate inside the lifters may be too great. There may not be enough time to refill with oil between each valve cycle, causing the lifters to collapse. Or if the bleed down rate is too low and the lifters retain too much oil, they can pump up and over extend the valves. Either way you can end up with valve float, misfiring and a loss of power.

Maybe an aftermarket Mallory. .. or something similar. .. that lets you set the max rpm desired...a shift light. ... definitely don't want to see you blow that beautiful new motor up buddy.

As far as I know, hydraulic lifter roller cams have less rpm capability of regular hydraulic lifters?

I am reading in many cam specs an rpm peak of 6,300 rpm. I think the issue is what RickP just described.

In the case of the roller lifter assembly they have more mass and that's what limits the rpm.

I do remember turning my engine into the low 7000s with a Crower hydraulic "280" lifter cam, anti-pump up lifters and triple springs with no signs of valve float.

If this is the case, the lifters are going to be your rpm limiter.


My friend owned the Flip's Speed Shop Pro Stock Camaro in the late 80s. The hardest thing in the world to find out was at what rpm they would launch the car and what rpm they would shift it.

Kenny Delco was the driver.

Flip would never tell me the launch rpm but what he said was that Kenny would shift the car when the nose of the car would dip down, i.e., the end of the power curve.

I'm not sure they actually knew the exact rpm that was either? The vibration in the car was so violent that my eyes couldn't focus on anything. I don't see how Kenny could read a tach under those conditions either?

They could just follow the "blurry light to the end of the tunnel", so to speak?

Thought I'd add that just for color?

Thanks, Rick and Doug.....

Me either.

intake valve float is not destructive, it is the natural limit of an engine assembled well. Exhaust valve float is TROUBLE.

Lifter collapse is the reason why hydraulic cams are not expected to rev beyond 6500 rpm, and one of the reasons why yours truly prefers to extend the rpm range with lightweight intake valves rather than heavier springs.

(the other reason is heavier springs equate to accelerated wear too)

By the way Rocky

Petronix manufactures a stand-alone rev limiter, employing the "random spark stealing" method of rev limiting, called the "Digital Rev Limiter".

$137 on amazon dot com.

There are two basic types of rev-limiters. The first simply cuts ignition power at some selectable rpm. This one will cause the car to lurch and radically increase a drivers heart-rate while possibly fouling plugs and generally being hard on components. Late GM cars cut the electric EFI pump off at around 5500 rpms.

The second type cuts only one cylinder, slowing the engine enough to get your attention. The more sophisticated of this type randomly cuts a different cylinder each crank revolution so all the plugs stay hot. Both work. I like rev limiters on 351-Cs; cheap insurance for my natural tendencies.

If you want to rig a 'Valet' switch on your car, connect the Holley's electric choke to the hot side of the ignition coil with a selector switch. This effectively rev-limits rpms to about 5200 no matter what other hi-buck parts you use.

FWIW, stock hydraulic flat tappets and stock valve springs conspired to rev-limit stock Panteras to about 5900 rpms even on the best- tuned motors. Changing springs raised the rev limits enough that otherwise stock engines started blowing up. Your real 'red line' is the strength of stock con-rods & stock two-piece intake valves, combined with stock unbaffled oil pan volume and the duration you keep your foot in it. Practically speaking, revving more than a few hundred rpms past the power peak of your cam in any gear only makes more noise, not more speed. This is where bad, noisy things start to happen.... Changing springs, con-rods, pans and carbs/cams starts you down the slippery slope of how-far-up-the-tach-scale-can-I-go-before-I-see-my-con-rods-outside-the-block. Good luck.

Well put BOSSWRENCH and comical last paragraph. It's always amazing to go to a drag race and witness the different stock classes at the starting line revving the engines so tight that one can hear the clattering of internal components. Luckily enough, the lights turn green just in time to put some torque against the over revving engine to bring some RPM down.

Pantera Electronics has a engine management system that has a built in rev limiter.
Engine Controller
Jeff

These heads are said to be good for at least 14,500 RPM......if you can get them. https://www.youtube.com/watch?v=ijj_E7TXsPE

quote:

Originally posted by OSOFAST:
Pantera Electronics has a engine management system that has a built in rev limiter.
Engine Controller
Jeff

Apparently this is one of the best kept secrets of this century? You tell Pantera owners about Pantera-Electronics and they just stare expressionlessly at you, then ask the same question again, and again? Scotty, beam me up. There is no intelligent life left on this planet?

quote:

Apparently this is one of the best kept secrets of this century?

Not to hijack this thread, but two new features of the Pantera Electronics Ignition Controller are a dedicated output for fuel injected ECU's (for precise timing of fuel and spark) and an engine oil pressure monitor that detects loss of oil pressure (and shuts off the ignition).

John