Anyone using Motorcraft AGSF12FM1?
- Thread starter mullens
- Start date
I think Justin at VMP is testing these plugs at .032 -.030, but he is over 17 psi. I would never run a gap of .040 at 15 psi. Reduce them to the smaller gaps I previously mentioned.
Last edited:
Can you educate me as to why? I admit I took a guess so I'd love to hear your thoughts
The higher the boost, the smaller gap required to prevent spark blow out. I've heard that when gaped too small, you begin to sacrifice idle quality. Mine are at .032 and idle like factory (NGK TR6).
Interesting Beast, so this suggests .035 might be too large a gap for 15psi and there might be some spark blowout. How to you measure/check for this?
beast is right thanks for the quick explain.
Yes normally at the top of the rpm band cause your forcing so much air inside. Also having a too big of gap at higher psi such as 15 an above will cause extra heat an cause the plug to burn or wear with a bigger gap faster also could get some detention cause the bigger the gap the bigger the spark.
I thought the NGK TR6 where the same heat range as the stock plugs?
My understanding with Justin was he was having to change the TR6s every 3K miles or so and he was trying these colder stock plugs to get more miles between plug changes.
My understanding with Justin was he was having to change the TR6s every 3K miles or so and he was trying these colder stock plugs to get more miles between plug changes.
The TR6 is the same heat range as stock. From what I've read .035 is a good compromise with moderately boosted (up to 15psi) engines. I know Justin has been playing with the Motorcaft plugs because the TR6's weren't lasting very long. I currently run TR6IX @ .035 but I want to try a cooler plug. The AGSF12FM1 fit the bill and are half the price of the TR7IX.
Last edited:
Thanks. I am currently running the TR6's @ .035 gap with 15 psi boost. Why are you wanting to try a cooler plug?
Just so all you guys know the TR6 are 1 stage colder plug than the stock gt500 plug now the BR7 are 2 stage colder plug. Also having to big of a gap for a certain setup or running race gas or torco will cause the plugs needing being changed most often.
Rule of thumb is to go 1 step colder with every 75-100hp increase. We have a big problem with detonation here in 91-only-Nevada so I want to keep those cylinders as cool as possible.
From NGK's site:
"An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug. A rule of thumb is, one heat range colder per modification or one heat range colder for every 75–100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber. "
I do believe NGK heat range 6 is the stock heat range for our engines (hate to disagree me32). Here are my reasons:
-NGK lists the TR6 and its variants as the stock replacement for the GT500.
-Motorcraft 22 heat range (stock) cross references to NGK 6 heat range, while MC 12 heat range (as in the AGSF12M) crosses to NGK heat range 7.
If someone can show me some documentation contrary to this, I'd be willing to listen.
Last edited:
If the gap is too large, you can experience spark plug blowout. You will see this as am obvious miss or hesitation at higher rpms. You will know ow if it happens. Over time, the gap can widen which may require you to swap plugs more frequently.
An important note, the stronger the spark, the bigger gap you can run. Also, e85 is harder to ignite, so that will limit your gap and probably plug life.
My experience with this comes from a much smaller motor, with a lot mote boost
An important note, the stronger the spark, the bigger gap you can run. Also, e85 is harder to ignite, so that will limit your gap and probably plug life.
My experience with this comes from a much smaller motor, with a lot mote boost
Then I got the wrong plugs from the factory cause the stock plugs that came out of my gt500 were the motorcraft 32 not the 22 you stated.
Maybe you did. I just looked at my stockers and they are MC SP405, (AGSF22FM1F4).
They are also listed as the stock plug for ALL GT500's.
I just LOVE spirited spark plug discussions!
Last edited:
My stock plugs were Motorcraft 22, so the TR6 is the stock heat range replacement. TR7 would be one step colder.
Users who are viewing this thread
