How do you determine red line?

[REDSC400]

Back in the day, (Ahem) there was a great book that I just cannot find right now that was written by a guy named Bell. It was called _Performance Tuning in Theory and Practice. The author suggested, at that time, what were considered some of the performance RPM limits for three classes of engines. The first class was standard stock cast-iron cranks and connecting rod engines. The second class was forged crank and heavy duty rod and engine bearing cap and the third class engine was the all out drag racing or blueprinted race engine.

The rev limits were a function of Mean Piston Speed.

The first class of engine should not exceed 3500 Feet per minute, while the second class should not exceed 3800 to 4000 F/m while the last class could attain speeds of 5000 to 6000 F/m for just a few seconds.

Mean Piston Speed, which is a measure of Feet per Minute is an esoteric calculation of

(2 X Stroke in Inches X RPM)
------------------------------------
12

or simplified as

stroke in Inches x RPM
-----------------------------
6

Therefore, if you know your engines stroke, and you enter into the equation the RPMs of your "theoretical redline guestimate", then you can calculate the Mean Piston Speed.

Once you get the Mean Piston Speed, you can then, based upon the discription of your engine, ie: (stock, forged, race) see how that compares to the suggested limits.

Now, you should err on the conservative side. I take no responsibility for your results. I do not know how valid Bell's guidelines are regarded by todays technology.

Bell, was also one of the first folks to write about using "seasoned" old blocks for racing vs new blocks. His theory was that the seasoned old block, having gone thru many many thermal cycles of hot and cold, had all of the casting stresses relieved. Thus the old block could and would maintain cylinder hone tolerances better that a new block which still had stress.

I do not know about that theory of his?

Hope this data helps?? If not it is at least interesting.