Odd vs. Even fire. Why?

[Jerryl]

What are the performance advantages and dis-advantages of either?

 

[Front Mount]

I'm sure others can explain this better then me, but my understanding is even fire makes the engine run smoother by spreading the firing pulses of a 90 degree engine block v6 to 60 degrees. Unfortunately they had to notch the rods to clear the crank or modify the crank - can't remember, and this makes them a little weaker. (At least this is what I was told by an old FORD mechanic a long time ago. I could be remembering incorrectly or even misunderstood him.) The odd fire has an odd firing order and may sound a little like a Harley with a not so even firing pulse but should have a stronger bottom end. Now maybe someone on here can explain it to me too, as I never really understood it or looked at engine parts to see if any of that is true. There may also be an offset of the cylinders with the even fire offset and odd fire directly across from each other in the V. Hopefully somebody on here will explain to both of us.

 

[delcowizzid]

oddfire fires at differing times its not at TDC every 120 degrees it has a shared bigend journal like a 350 chev its probably stronger at the crank journal but not very smooth. sound v8 ish.evenfire has split crank journals making tdc at 120 degrees on all cylinders but it near halves the material at the crank journals for the bigends from the offset.neither are as smooth as straight 6 or 60 degree v6 which once again has a shared journal for 2 bigends but the V angle being 60 degrees makes it even fire

 

[we4Mateo]

Interesting. Thank you.

 

[Jerryl]

Both have made plenty torque. I think to know the answer, but was wondering: Which is capable of producing greater output and why?

 

[HighPSI]

The even fire crank is weaker. On an off center block the rods aren't centered over the bearings. The odd fire requires some serious ignition mods. The odd fire idles slightly rougher. 99% of Buick owners would never need the added strength of an odd fire crank. I have yet to do back to back tests, but believe the odd fire might make slightly less hp.

 

[Jerryl]

Thanks Cal for confirming my thoughts.

 

[turbofabricator]

According to Dr. Duttweiler the even fire crank is on its last leg around 1600hp. The odd fire crank will live at 1,980 HP on his dyno. The #5/6 crank pin is where the even fire cranks fail. It is little football shaped area that is trying to transfere all the power of the other cylinders to the flywheel flange. Pretty amazing that you can run 1600 HP through that tiny section of crank. Very amazing. Chinese cranks need not apply here.