> From: akguc!tdm@akgua.att.com
> Date: Fri, 22 Oct 93 09:01 EDT
>
> "Is it even-fire or odd-fire?" I obviously don't understand this.
> My MGA seems to do a little of both. Would you explain ?
>
>
The ideal V-angle for a 6-cylinder, four stroke engine is 60 degrees.
(also 120, 180, etc.)
The idea V-angle for an 8-cylinder engine is 0, 45, 90, 135 degrees, etc.
V6 engines with a 90 degree split, and common rod journals, (normal on a V8,
see early Buick 231) are "odd-fire" because there is no way to time the engine
with the exact same angle of rotation between power strokes.
V6 engines with a 90 degree split, and "split" journals, (two rods on the same
journal are not concentric, see late Buick 231) are "even-fire" because the
"wrong" angle used for the V is corrected by the split crank. They have
120 degrees between every power stroke.
Engines with the correct V angle are inherently even-fire. No correction is
needed. (they can have common/concentric rod journals)
Later,
Kevin
P.S. the reason I asked is: When Buick "split" the crank on the 231, they
had no choice but to make the main bearings narrower to make room.
This makes them a very bad choice for performance. (low surface area)
P.P.S. Does anyone know how reliable the main bearings/oil system is in the
3.5 aluminum V8? I know the Buick V6 is basically the Buick 215 V8
with 2 cylinders lopped off, but I've never heard anything good or
bad about the mains in the odd-fire V6. (The even-fire V6s are terrible)
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