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Old 08-12-2008, 09:04 PM   #1
Tiger II
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Default even fire vs odd fire

So a discussion came up regarding odd and even fire. Supposedly the Viper V10 is odd fire and the Ford Triton V10 is even fire. Any of you smart folks out there explain the difference.

Thanks
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Old 08-12-2008, 09:13 PM   #2
btbsandman
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Default Re: even fire vs odd fire

Well I have the 198 V6 oddfire Baby Nailhead in my 1962 Buick. The oddfire has more "rumble" that can be felt in the car when idling at a stoplight. It has a more throaty sound from the exhaust.

I took this from a Buick Board that describes the oddfire issue in the V6...

"The firing interval that proved best was every 150 and 90 degrees for each crankshaft throw with a cylinder firing order of 1-6-5-4-3-2, alternating between the cylinder banks. "That was a little bit different than people were accustomed to, and if you sat in the car at idle you had a kind of little dance that you went through, so we said it had a personality of its own."

I have no clue about the evenfire stuff....
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Old 08-12-2008, 09:19 PM   #3
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Default Re: even fire vs odd fire

Simply put the even fire engine fire in even degrees of crankcase rotation etc. The odd fire engine are uneven spaced firing events.
Chevy and buick both made some odd fire engine over the years as well , the odd fires ran ok but were a little rough at idle.
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Old 08-12-2008, 09:20 PM   #4
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Default Re: even fire vs odd fire

Kind of Depends on the angle of the V of the block. V8's are even at 90°, V6 and V12 are even at 60°. When a V6 is based on a V8 block, they are 90°, so they are odd-fire, unless the crank has the pins offset to make it even. Both the V-10's mentioned are 90° blocks, Ford uses offset crank pins, Dodge does not.

Here is an even fire 90° V6 crank. Funky stuff going on with journal offset.


Last edited by Relic Stew; 08-12-2008 at 09:32 PM.
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Old 08-12-2008, 09:34 PM   #5
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Default Re: even fire vs odd fire

Chrysler/Dodge ran the 3.9L v6 which is an odd fire engine for years, actually until 2003 I think in Dakota pick-ups. Just did training for Chrysler cam in block engines and they mention nothing about odd firing engines on the new Viper 8.4L. It does have variable valve timing though, which is insanely awesome in it's simplicity. Kinda makes me angry none of us thought of it first.
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Old 08-12-2008, 09:46 PM   #6
hotroddon
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Default Re: even fire vs odd fire

Since you asked about V-10's
The Viper uses common crank pins which creates a 54 degree -90 degree firing order as that's when the pistons come up due to the common crank throws, hence ODD Fire.
The Ford uses split crank pins that bring the pistons up every 72 degrees, hence EVEN fire.
At least that's how I understand it.
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Last edited by hotroddon; 08-12-2008 at 11:00 PM.
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Old 08-12-2008, 10:52 PM   #7
no55mad
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Default Re: even fire vs odd fire

As said above, with the Buick V6's, the odd fires had two rods on one crank journal like the V8's. The even fire V6's had a seperate crank journal for each rod.
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Old 08-12-2008, 11:55 PM   #8
RAG66
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Default Re: even fire vs odd fire

Oh man,
You guys on here scare the crap out of me with all the smart thinking & tech knowledge! Great stuff I didn't know I needed to know!
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Old 03-12-2009, 11:43 AM   #9
BeatnikPirate
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Default Re: even fire vs odd fire

I dug up this old thread because the new "Street Rodder" mag has an artical on a 32 Ford modified with an "Indy inspired" odd-fire V6.
It says that AJ Foyt and others used Buick and Chevy powered race cars using an odd fire arrangement to create lots of horsepower.
The artical says that ,with the odd-fire design "groups of two cylinders are separated by 90 degrees of rotation (like in most v8 engines) with other groups separated by 150 degrees of rotation (it's 1-6-5-4-3-2 firing patern requires 720 degrees of crank rotation for all cylinders to fire)."
I don't get it. Does this really produce more power? If so, can someone please explain how this is and how come more engines aren't set up this way? Thanks
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Old 03-12-2009, 11:56 AM   #10
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Default Re: even fire vs odd fire

i could be wrong but seems to me all motors take 720 degrees of rotation to fire all cylinders
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Old 03-12-2009, 11:57 AM   #11
r759ca
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Default Re: even fire vs odd fire

oops edit that, that is unless they are two stroke engines
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Old 03-12-2009, 12:38 PM   #12
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Default Re: even fire vs odd fire

The other issue is strength, common rod journal (odd fire) cranks are stronger
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Old 03-12-2009, 12:57 PM   #13
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Default Re: even fire vs odd fire

Here is my 259 inch 1979 Buick even fire v5. it was the protype for the Indy and nascar stage 2 motors. it had 1.88 inch intakes and made 350 hoesepower on gas. it also has a dry sump oil sPhotobucketystem. the lower end is good for over 8000 rpms.
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