67King

I've never heard of ANY DAMB system using roller "buckets". Does such a creature even exist? RFF, sure. Pushrod, sure. Not buckets, though (to my knowledge).

George D

This is the biggest reason the factory lifter system is good enough. I believe LR has an oiling solution for higher RPM's, but most of what these motors have to offer is prior to 7K.

There are PLENTY of other options for a well sorted/high RPM car that is fun to drive and track.

I have a few friends that installed solid lifters in their 3.0 motors, and thought lifter noise was piston slap. When I asked their RPM limit of the build, one stated, "Once I get the oiling issues figured out....???? Now he has another piece of his car that has to be monitored, adjusted, and kept up to spec. Not worth the hassle.

There was an article in one of the recent European Car rag that had a 800hp daily driven TT. They went through three engines to get the RPM up high enough to get the power. They found that around 7800rpm, the oil started going backwards. They fixed the problem, but THREE custom built motors, engineering time, and dyno time is about the cost of one decent modded TT with reliable 600WHP purchased new then modded.

These cars are fun, but wanting more than engineered into the system will COST many times more than just getting the right car up front. There are plenty of killer sports cars that will rev well past any 951.

Know, RPM does not mean faster. Diesel technology is kicking serious ***. Look at their max RPM. Someone stated, "TQ wins races and HP sells cars."

George

TurboTommy

So what is the official RPM limit of our oiling system?
Let's call it in 3 stages:
1) to what RPM limit can you take our engines and always be safe even in relatively sustained situations?
2) to what higher RPM can we take our engines to for brief bursts and still be okay?
3) after what RPM is engine failure to occur in a very short time?

V2Rocket

Seriously...my friend has an Excursion with the 6.0PSD with nothing but a factory ECM re-flash and a 4" turbo-back exhaust on it and puts out 400HP/600TQ, yet revs to 3500RPM max...

George D

Trust me, my GMC 2500 in 4X4 with a boost load on the brakes will kill my 951 to about 30mph. All tires smoking is fun as hell. This is at 8500'.

TonyG

I raced for several years, two cars, both of which made big power up top, and both shifted at over 7000 rpms for years without oiling issues. All I ever had was a boxed oil sump and "ringed' oil pickup tube, and a cross drilled crank. Other than that the oiling system was stock.

And these engines used bone stock hydraulic lifters too.


TonyG

333pg333

How would dry sumping help?

Chris White

The ‘official’ RPM limit would have to be were Porsche set the redline!
OK, here is my view on the whole thing…which will not get you an exact RPM answer!
The stock 951 engine will rev quite high without an immediate mechanical failure if it is with all other good operating parameters. My guess is that you could see higher than 7500 without something breaking. However, there are many issues that will pop up. –
• The entire system (induction, cams, head, valves, guides, exhaust, turbo and engine management) is designed for midrange torque – so optimizing for anything over 6500 will require major changes to the design.
• The oiling system is crank driven and it is not designed for high rpm use. The pump is known to have a cavitation issue when run outside of its design parameters.
• The valves are relatively heavy and the guide wear goes up exponentially over 6500 rpm.
• The rods and pistons are quite heavy and not conducive for high rpm use.
The most likely failure for high rpm use is an oiling system failure – and that has so many variables that you can only set a very conservative ‘red line’ if you want it to be ‘fool proof’. What are the variables? –
• Oil temperature (changes viscosity)
• Air entrainment in the oil (foaming due to crank contact and windage)
• Lateral and longitudinal G forces (oil pick up exposure is not as big a problem - displaced oil being whipped up by the crank is a problem for track cars)
• Less than optimal oil passages in the crank – by itself this is not serious, but with the above issues it becomes a problem.
If I had to quote limits for a stockish engine I would say that you could run 7500 on an engine dyno with nicely controlled conditions. On a track you are at risk anytime you are over 6500. If your other parameters are well under control (temp and foaming) then you can run 7000 without substantial risk.

All that being said there is a big contradiction – running a stockish engine over 6500 does not provide any real power benefit since its outside the power band. Once you start making major mods you have changed so many parameters that a general statement about ‘redline’no longer applies….

Chris White

Yes.

TurboTommy

Yes I realize this.
I'm assuming all mods to provide sufficient air flow are in place (in order to WANT to run higher RPMs). So, I wondered at what RPM our stock oiling issues would hold us back.

very informative

TonyG

Exactly.


When you have a engine that is capable of making HP at the RPM point where solid lifters are a necessity, you no longer have an engine that is remotely close to stock.

TonyG

gt37vgt

the most cost effective way to increase breathing and rpm of the head is to bolt a 16v on

333pg333

Yes...or just remove the valves completely...

MooreBoost

so would i need solid lifters if my engine was spending most its life in the 4k to 8k range? i would like to make my shift point around 7500. rods, dry sump, ti stuff are on the list. i was told that the hydraulic lifters will work..

m42racer

My friend, with all due respect, you have a truck engine and an old one at that. You can throw all of the latest gagets and gismos at your engine and it still will be a clunker. As long as you understand this you will be fine. There is a saying that has silk purse and sows ear in it.

These engines unless you spend huge amounts of money and change the whole bore and stroke sizes, fit multi Valve heads, the engine will be limited to RPM. You have one of the heaviest 4 Cyl Cranks known to man and 100.00mm Pistons just slightly lighter than a 1gal can of Lowes paint. The RPM will be limited by the manifold and heads ability to flow enough air for high RPM's. The stock Oil Tappets are good for well above the RPM these engine are good for. Ti Valves are good if you can afford them, but I would take the bet that they will never gain you a dime of performance if the stock Crank is still rotating within your engine. Maybe if you were to reshape the valves for better air flow they would help, but not for any recipocating gains. Solid tappets are worthless unless you have changed a whole lot of the other parts. You will be absolutely fine with the hyd ones. Make sure the engine is well built first, then start adding in the fancy parts. There are too many customers sucked into buying parts off the internet from vendors who don't know their *** from their elbow. I can think of one but if I named them this post would never be read.