Odd or Even 231?

I got a hold of a 231. By block casting # it is a 77. Is there any way to tell if it is odd or even fire without checking the crank #? The distributor is not with it.

 

If you don't have the distributor the best way is to check the crank. If every connecting rod has its own journal it's an even fire. If each journal is shared by 2 connecting rods it's an odd fire. '77 was the transition year. First part were odd fires and last part were even.

 

Thinking SBC?

 

I'm no expert on this, but I understood that the simple crank on the odd fire is what makes it odd. A 90 degree V with journals separated by 120 degrees gives an uneven combination of firing angles.

 

Thank you, I'll pull the pan.

 

Just pull the distributor cap and see what it is.

 

Uh, his post says there is no distributor with it. How can he pull the cap to check it?

 

I guess I missed that part.

 

Odd it is, Thanks everyone.

 

So there's no way to determine whether it's an "odd-fire" or not unless you pull the pan? Does the firing order change between odd and even blocks...? I was hoping I could tell by that. I just had to replace some fuel lines today and I was wondering what I had in my '71. Someone has already installed a Petronix distributor setup in this one.

Thanks,
Jeff

 

If you have the distributor you can tell if its oddfire or evenfire by looking at the rotor and point lobes or the stator ring and cap if its electronic. The oddfire and evenfire both have the same firing order. You can also run the serial numbers on the block, if its older than 1975 it can only be an oddfire unless someone has swapped guts out of the motor (unlikely though). 1977 was the transition year between oddfire and evenfire and without the distributor the crank is the only way to tell. Run the casting numbers if the motor is a 71 then its oddfire only.

 

Not sure this would be 100% correct as most marine engines had points long after HEI came out. Don't know when they quit using 231 motors in marine use. Unlikely you would have one in a car but anythings possible.

 

I'll run the casting numbers and see. My CJ6 is a 71, and my Jeepster a 69. Both should be original..."should" being the key word there.

Is there a benefit to having one over the other...odd or even fire?