Going Odd Fire

[CTX-SLPR]

Howdy,

As some of ya'll may have seen, I'm in the planning stages of a LSR build. Now I'm going to have to use a stock block to start with as I don't have the funding for a Stage or TA block especially since I have to run a block with stock deck height and cam location to be considered for Production classes. However since I'm going to be running a carb and am seriously considering going oddfire, I figure this is the place to ask questions.

I understand that the oddfire crank is stronger than the even fire by virtue of it's paired rod journals. This could be an aftermarket unit or a stock 225 unit if I decide to race with the "big" 184-260cid motor. I have a few questions though.
What are people running for a distributor? I'm theorizing that since the firing pattern is like a V8 with 2 cylinders gone, I could take a V8 unit and just remove the terminals and/or the reluctor teeth to get one to work. Otherwise is it just a Jeep points unit converted or an early 231 HEI?

Are oddfire rods "on center" or "off center" and what is the rod journal size for most of the aftermarket units?

I know the cam is different both in nose and lobe configuration but are there any other valvetrain hang ups?

How is the high rpm stability of the oddfire compared to the evenfire? Is it anymore stressful to the block?

By chance does anyone know if the production oddfire stuff takes V8 (300-340-350) balancers and flexplates?

Thanks,

 

[HighPSI]

What are people running for a distributor? I'm theorizing that since the firing pattern is like a V8 with 2 cylinders gone, I could take a V8 unit and just remove the terminals and/or the reluctor teeth to get one to work. Otherwise is it just a Jeep points unit converted or an early 231 HEI?

Because it's odd fire, the cylinders fire 90-150-90-150-90-150, not every 120 like an even fire. Because of this, you can't just remove terminals and reluctors. If you are using the distributor for your crank signal, you will need a distributor with the reluctors spaced 90-150-etc... There are two ways to do the cap. The best way is to adapt one off an AMC with the post spaced 90-150-etc.. Then your rotor phasing will be much better. The other method is to use a standard cap with a rotor with a long tip on it. This method is prone to misfire if you have a wide range of timing you are trying to run

Are oddfire rods "on center" or "off center" and what is the rod journal size for most of the aftermarket units?

Rods are "on-center" and the rod jornal size is usually stock.

 

[CTX-SLPR]

Because it's odd fire, the cylinders fire 90-150-90-150-90-150, not every 120 like an even fire. Because of this, you can't just remove terminals and reluctors. If you are using the distributor for your crank signal, you will need a distributor with the reluctors spaced 90-150-etc... There are two ways to do the cap. The best way is to adapt one off an AMC with the post spaced 90-150-etc.. Then your rotor phasing will be much better. The other method is to use a standard cap with a rotor with a long tip on it. This method is prone to misfire if you have a wide range of timing you are trying to run.

When I said removing reluctors and/or terminals I was reffering to a V8 distributor, not an even fire. The AMC you are reffering to is the Jeep 225 Dauntless V6?

 

[HighPSI]

When I said removing reluctors and/or terminals I was reffering to a V8 distributor, not an even fire. The AMC you are reffering to is the Jeep 225 Dauntless V6?

I knew you were talking about a V8 distributor. That won't work because the reluctors in the distributor are 45 degrees apart. You might be able to get two cylinders correct, but the other 4 will be in the wrong place. A V8 distributor will have a pickup at 0-45-90-135-180-225-270-315. An odd fire V6 will have a reluctor at 0-45-120-165-240-285. The same goes for the cap spacing.

Yes, I was referring to the Jeep

 

[Mike E]

Removing terminal from a v8 distributor won't work. The v8 crank has rod journals 90 degrees apart and cylinder banks are 90 degrees apart. The odd fire v6 has the journals 120 apart. But, since the banks of cylinders are 90 apart, you get 90 degrees between firings for the two cylinders that share a common rod journal. Then it's another 150 degrees before the next cylinder fires.

Lto R: Even fire v6, Odd fire v6, v8

 

[HighPSI]

BTW: If you elect to go fuel injected, I have an odd-fire XFI flash that allows you to run a stock 87 crank sensor and pickup along with a standard distributor just using an AMC cap.

 

[CTX-SLPR]

Thanks, I'm not sure why I wasn't able to put all the pieces you listed and I knew together into the right picture for an oddfire setup. Sounds like if I do buy the 225 oddfire crank from the local guy I need to get his prestolite distributor as well.

I'm doubting I'm going EFI as that pushes me into competition with the likes of the R35 Skyline GTR and the 2JZ-FE Supra depending on displacement but worth knowing.

 

[BlownV6]

Because it's odd fire, the cylinders fire 90-150-90-150-90-150, not every 120 like an even fire. Because of this, you can't just remove terminals and reluctors. If you are using the distributor for your crank signal, you will need a distributor with the reluctors spaced 90-150-etc... There are two ways to do the cap. The best way is to adapt one off an AMC with the post spaced 90-150-etc..

Cal, Are you saying that AMC had an oddfire cap , with oddfire pole spacing?? If so I certainly wasnt aware of that. but would very intrested in a part number or a pic. I use a Volvo oddfire cap that I custom made my combo fuel pump/distributor setup with that cap. Msd made oddfire distributors but used a standard evenfire cap. With a locked in timing setup there is no problem with spark crossfire as the spark occurs just before 3 terminals and just after the other 3 terminals. Mike

 

[HighPSI]

Argggg. You are correct Mike. It is a Volvo cap not an AMC. It's been a while since I messed with an odd fire set up. Sorry for the mis-information.

 

[BlownV6]

Argggg. You are correct Mike. It is a Volvo cap not an AMC. It's been a while since I messed with an odd fire set up. Sorry for the mis-information.

Since I was an AMC guy before becoming a Buick guy. Actually I put a Buick v6 in my Supergas Gremlin. I though you had one on me!!! No harm no foul!! Thanks Mike

 

[fuzzyGN]

I have a complete Odd-fire 231 if you are looking for an engine, about a 1976 or 77 I think. 2bbl carb and everything. Still have the distributor, pullies, etc. I even have a stock 4bbl intake and carb from a 4.1l too. Let me know if I can help. I am in Southern NM about 30 miles from El Paso Tx.

 

[CTX-SLPR]

I might be interested though at this point I think I'm going to be doing a 2.66in stroke 181cid motor to keep my initial expenses down by racing against slower records with less safety requirements. Still a possiblity that I'll go with an oddfire motor but that'll take an aftermarket crank for sure since the 181 was evenfire only from the factory and the 196's stroke is too long.

 

[CTX-SLPR]

Oddfire crank purchased! Now I've got to assemble the supporting cast. Know I'm going to use a TA chain and tensionser and I'm going to hunt the junkyard this weekend for a Buick oddfire V6 distributor.
Since this is a BMS piece should I expect a neutral balance unit and need to hunt up a BHJ or the Indy Lites balancer?
Any other parts specific to the oddfire (BMS crank specifically) that I'll need to hunt up?

Thanks,

 

[BlownV6]

I have stock buick oddfire distributors on my shelf I will sell one for $25.00. There is also an MSD oddfire distributor on e-bay right now that goes in a couple days item #281083116737 Mike

 

[daves87gn]

i have one of those BMS hubs if you need it $75

 

[BlownV6]

I have stock buick oddfire distributors on my shelf I will sell one for $25.00. There is also an MSD oddfire distributor on e-bay right now that goes in a couple days item #281083116737 Mike

Well I just looked in my distributor pile , and I have that exact same MSD distributor. So I could also fix you up!! Mike

 

[CTX-SLPR]

Mike, Did you have any problem fitting rods in your oddfire engine? With the BMS stage 1 pistons I have and traditional SBC rods the small end of the rod would run into the pin boss before the rod would fit on the crankpin. Even with offset SBC rods (0.035in offset to the center) it would be tough fitting them.

 

[BlownV6]

Thats why I originally suggested using a BBC chevy rod for a 2.100 crank pin. That rod would be .990 wide and you could easily narrow it to .940 wide and get the beam centered up on the piston. Yes it requires a bit of machining but thats what it going to take !!! Mike

 

[BlownV6]

Also I use an on-center block. My rods are perfectly centered on themselves as far as no offset whatsoever. This puts the center of the small end within a few thousands of being exactly centered in the piston. Mike

 

[CTX-SLPR]

Yeah,

I have a rules committee ruleing that On-Center blocks are not legal in the production classes which is going to be my primary home. I've got a few RFQ's out for 0.100in offset SBC rods.

Going to be digging through the yard for an oddfire distributor today but how much do you want for your MSD?

Thanks,