Spark plugs?

[gtxno1]

Hi everyone what spark plugs are you running in your mild 440's stock or something different thanks

 

[Dennis H]

N G K's.

 

[doublekrossd]

I run NGK R5671A-7 or 4091 (two numbers same part) in my Indy headed 440. I think its mild but others may not...

 

[HT413]

I'm running champion RC12YC for their extended reach needed for the Stealth heads. I used to run a set of shorty plugs with a pair of 906 heads to better clear the headers. Can't remember the part number, let me see here...

 

[Dennis H]

My Tuner at Valaya Racing here in San Jose went nuts when finding out there are Japanese plugs in the 440. But, I can't mess with success. The crisp idle and overall performance improved when these were installed.

 

[gtxno1]

Using old school Iron 915's are the plugs the same size thanks

 

[Moparsmitty]

I've been running Champion RJ12YC plugs in my mild 440 for many years without any problems. When you are changing plugs, take the time to give them a close inspection before installing them. I know from experience in the business that shippers and parts stores aren't always as careful handling their stock as they should be. Make sure that they don't have any hairline cracks in the insulators and that the gaps are correct. Changing plugs on a big block B body can be kind of a bitch, especially if you have headers, but take your time and do it right. I've had several cars in the shop that were running poorly because the plug were damaged or not installed properly.