Revving it up
Well for most hi rpm production V-8's (american), due to mass production balancing methods, and materials used, and the assembly methods, it seems that somewhere between 6-7000 RPM is about all the factory parts will handle with any reliability. After that, inherrent imbalances, start becoming serious and come into major play. Generally, production parts arent designed to handle those kind of RPM with reliability.
Getting over 8000 RPM, does require, mainly, serious balancing of the parts. While this isnt the complete story, imagine 5 grams variation of weight at 0 rpm. Due to rigidity of the crank and block, this isnt a big problem, but when you start turning that crank up 8000 rpm, that 5 grams of weight, start taking on centrifical weights of very large proportions, for the same reason that generally an RPM ceiling of 6-7000 rpm starts tearing stock engines apart. Rod bolts stretch, pistons start separating at the ring lands, valve trains start to float, You get the picture.
Now turning over 8000 RPM, you run into other things like the centrifical weight of the crankshaft itself. The counter weights start taking on weight proportions that are tonnace.
Main cap bolts start stretching due to the forces on them and the next thing you know, a crank ventilates the oil pan.
Hense, to get into those kind of RPM's does require balancing and stronger fasteners. Other factors are the oiling systems ability to recover lubricant, without airiation, to maintain its ability to keep the bearings and steel from coming int metal to metal contact.
As I mentioned in my previous epistle, I did turn these higher RPM's with production parts, albeit with a good balancing job, and the proper fasteners. This even included running production rods and pistons. Turning an engine into the ionosphere does put a lot of wierd stresses on it, from the foundering of the block, as well as all the moving parts. Thats why you see guys putting special alloy rods, cranks, pistons etc in their engines for reliability, as well as installing main stud girdles, windage trays, oil scrapers, etc.
It not difficult to turn an engine 9000 RPM if you have the basic parts to do it, like cam grind, valve springs, lifters, carburation, air flow etc, but if you do this with an engine running assembly line internals, you are asking for a hand grenade with the pin pulled out. The trick is to keep the engine together when you do it.
Harmonics is another equation. When you start turning things hi RPM, ( take a stick and tie it to a string and spin it around your head sometime at variing speeds, you hear different tones), these can tend to cause crystalization of the metals in your engine, causing failure. If youve ever wound a 4 or 5 main inline 6 up anykind of RPM, you will know what I mean, as you can start to feel them, at relatively low speeds. The reason that you will feel them in a 4 or 5 main inline before you will in a 4 main V-6 or a 7 main inline is because due to the lesser crankshaft support of the fewer mains, you will have more crankshaft flexing and at lower RPM. The reason this isnt such a serious problem with V-6's, is due to the shortness of the crank, and having as a rule 4 mains to support it. More rigidity.
