Curious, I've never come across (atleast I dont recall seeing it in rave or the manual) the factory recommended dne (do not exceed) aka red line or continuous load caution range (yellow). My tach is solid colors with no markers, all I know is peak hp is rated at 4,750rpm so I'm assuming 4900 or 5k would be the magic bullet. (2,600rpm is the torque peak for anyone whos interested)

 

I'm kinda curious myself.. especially since mine hasn't exceeded 3009rpm since I bought it in january.

 

With the Rover engine's long rod and (comparatively) short stroke, these engines are prime candidates for sustained high RPM operation without the potential for self destruction or significant premature wear.

What plagues this engine obviously is that it simply will not flow enough air at high RPM to make any reasonable power up there. Plus the OHV pushrod design is quite ill-suited for sustained high RPM operation, and you run into valve float and other headaches at high RPM, whereas an OHC design would have been much better.

To put it into perspective, the rod/stroke ratio on this engine is over 2.0:1. Simply divide the rod length by the stroke. Rod/stroke ratio determines the rod angle at a given point in the crankshaft's rotation. It's essentially how much force is being applied sideways (toward the cylinder wall) instead of down against the crankshaft. Higher angles = more thrust against the cylinder wall, which you guessed it, causes greater wear.

A high rod/stroke ratio implies that the rod angles are shallow (rod is more vertical through an engine's stroke), and because of this, they will generally tolerate high RPM's much better, with lower wear, than an engine with a lower rod/stroke ratio.

The short stroke of the Rover engine also means the piston speed is lower (less distance to travel in one revolution) for a given RPM than a long stroke engine. The rover engine is VERY much oversqure (larger bore than stroke), so again, an attribute very much in favor of sustained, high RPM.

Most production engines fall in the range of 1.50 - 1.750 rod/stroke ratio. A GM 454 is about 1.48:1, which is at the low end of the spectrum of production engines. That low ratio is not a bad thing on a big block, as it spends very little time above 3k RPM. On the other end, a Ford 460, and many VW engines (like the VR6) fall around 1.75:1, which is at the high end.

You rarely come across a production engine that's over 1.75:1, which is why the Rover is such a jewel in this regard.. It's too bad the engine has so many other problems (like HG, cracked blocks, slipped liners, etc.), because it has all the right attributes for a very low wearing engine (especially ring & cylinder wall wear).

So in essence, I'm not sure this engine has any hard fast "redline." With such low piston speeds and shallow rod angle, you could rev it to the moon and probably not break anything-- but you'll never get any power out of it past 5k or so.

 

i believe in one of the many books Ive read that the V8 ECU has a rev limiter set at 5k -5.2k

 

Generally, the criteria for rev limiter placement is as follows:

a) the point where engine wear / stress becomes unacceptable (piston speed and side loading are some primary concerns)

b) where no more useful power can be obtained by an increase of RPM

Usually both are in the interest of engine longevity. I think the fuel cut on these engines is right after 5k.

 

I think the formula that Land Rover used was more like "we have to warranty this engine, when are we going to shut it down?".