Tach redline question C2s

[Donald H.]

Probably a dumb question and I did a search of the TDB but didn't find an answer.

The C2 base engine, i.e. 327/300HP, tach is referred to as 5500 redline; however, the red range starts at 5300 and runs to 5500.
The 327/350HP tach is referred to as 6000 redline, and does start at 6000 and runs to 6200
The 427/425HP and the 327/365HP tachs are referred to as 6500 redline and the range does start at 6500 and runs to 7000.

So why is the base engine tach referred to as 5500 redline when it really starts at 5300?

The reason I ask is that I am going to look at a car hopefully this weekend if we don't get another dumping of snow. The car is advertised as a 350HP car. Its a 66 with a 67 block and stamped as as 67 300HP (V instead of F leading character on the pad) from the few pictures I have seen. The owner know little to nothing about numbers and specifics of C2s.

Thanks,

Don

[Duke W.]

Re: Tach redline question C2s

Probably a dumb question and I did a search of the TDB but didn't find an answer.


So why is the base engine tach referred to as 5500 redline when it really starts at 5300?

Don

Because a lot of guys just don't pay attention to the details. The OE redline is the point where the red zone starts, which is 5300 on a 327/300, however the practical redline is where the engine no longer produces useful power, and a shift to the next gear provides greater power. On an OE 327/300 this is about 5000 revs.

Conversely, if a OE 327/300 engine is rebuilt with better connecting rods, massaged heads, A McCagh Special camshaft, and careful attention to installed valve spring height it will look and idle just like an OE 327/300, but it will make useable power to about 6500 with lifter pump-up at about 67-6800.

The "design speed" of an engine is determined by maximum safe stress of the cranktrain and/or valvetrain components, but depending on configuration the engine may run out of useable power below this speed, or it may be still making useable power above the design speed.

Duke