Open Animal build help

[Jimbo]

Charger
The stock champion or cross reference it to another plug will work.
I usually use an RN 9YC but depending on how things are done sometimes indexing washers are necessary.
I have had engines where even if you use the RN 9YC or the 12YC it can be so close that you want to make sure the piston isn't at TDC when you take the plug out or put it in. Not the ideal situation but sometimes someone else has done things before I get to it. It's an alternative rather than start allover again with a new head, block or piston.
You can index the plugs with a single ground electrode like a RN 9YC but not a 3910X since it has 4 ground electrodes.

 

[Charger128]

Alright, thanks for the help. I def want to avoid blowing the motor up from something minor like that which can be and easy fix.

 

[kartboy63]

Good luck on flathead crank unless you go billet

we broke them cheap A###S ARC cranks that dont cost cheap, but never broke a flathead crank

 

[CarlsonMotorsports]

we broke them cheap A###S ARC cranks that dont cost cheap, but never broke a flathead crank

You are breaking the "billet" ARC cranks?
Are you using a 3rd bearing support?
Surprised, but then again, nothing is 100% failure proof in a race engine.

 

[Skidude]

we broke them cheap A###S ARC cranks that dont cost cheap, but never broke a flathead crank

Wow! I’ve never run the ARC’s but I’ve broken 2 flathead cranks in flatheads. But like Brian said, nothing is fail proof in a race engine.

 

[One Fast Kat]

I had a friend one time. You could give him a rubber hammer and an anvil. He would break the anvil. Every part has critical fail point. How it is treated, installed and cared for makes a difference. And then there is the chinese steel that we get that is all over the place as far as quality. Just ask any welder or fabricator.