11-26-2007 Now don't go confusing me with facts
There are a few things that set the redline such as the loads (reciprocating weight), the piston speed, the strength or stiffness of the block and crank, life expectancy requirements, valve train and such.
On piston speed an 86mm stroke should be safe for extended use to about 8500 rpm, maybe a little more. The load on the block and life would be the only concerns I think…which are not trivial but at least the pistons won’t fly apart. Ti rods or even new steel rods (I’m told they save about 100 grams) would make me feel better about the bearings living a reasonable time at that rpm, but it shouldn’t come apart I don’t think. Heck even the nascar boys run an 89mm stroke all day long at 8000 rpm with steel rods….but I’ll bet the bearings are all done at the end of the day.
I don’t see it spending a lot of time at up there anyway because I think it will stop making hp above 6000 or maybe 6500. The heads flow what they flow and a 6 liter engine will use it up at about 25% less rpm than a 4.8 liter would. I though I could get the 4.8 to pull to 8k, but with the same heads a 6.0 will be done at 6k. Unless I can get more air through the heads somehow 8k will be short burst because I want to hear it, but the real shift point will be around 6500 to maybe 7000 if the heads come out great.
The advantage in my mind to the larger engine is about 25% more torque everywhere and that is really nice in a streetcar. It’s nice to down shift because you feel like it, not because you have to.
I will change the rods if there is anyway to fit it in the budget, if not I'll just keep the revs down to something reasonable most of the time I guess.
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