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Hi guys me again. I have the 89 mustang 5.0 gt40 heads with a on3 turbo kit 70mm. What are you guys gapping your plugs to. I gap mine at 28 is that ok?
 

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From what I remember, .028 should be an alright starting point for up to 9-10psi. might hit a rev limiter. not 100% sure though
 

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Yes, compression, plug heat range, fuel type and boost level will effect gap needed. For best power and driveability you want the widest gap that wont blow out under full boost. Generally for 10psi range you want to start in the .030-.032 range and gap down if needed.

I ran .032 no problems at 10-12psi when I went up to 14psi I got spark blowount so I gapped down to .028 to get up to 18psi.

For reference my setup is stock heat range plugs, 9:1 compression and I switch between e85 and 93.

If you run higher compression or colder plugs etc that will affect the gap you need.
 

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I run mine at .032 with 11psi
 

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we run them at .022 with more boost than any of you have posted... and more compression...
 
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Many factors associated with plug gap for sure. I run a Crane HI-6 ignition box which really seemed to help with resisting blow out. I've run .032 gap all the way up to 15 psi with no issues, but at 22 psi I run my gap at .026 with no issues.
 
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Had good luck anywhere from .025 15+ PSI stock ignition system 351
 

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I target .028-.032 gap and have 25 psi on an 8.5 compression motor at 7500+ RPM. I have a CD ignition of modest size, but it was also fine with the Ford TFI system and MSD coil. C16 fuel. 22 degrees timing.

If a system is gap critical..... the ignition is too weak. I can gap my plugs at .040 (wide as I tried) and not miss a beat.
 
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I target .028-.032 gap and have 25 psi on an 8.5 compression motor at 7500+ RPM. I have a CD ignition of modest size, but it was also fine with the Ford TFI system and MSD coil. C16 fuel. 22 degrees timing.

If a system is gap critical..... the ignition is too weak. I can gap my plugs at .040 (wide as I tried) and not miss a beat.
Then your gap should be .040 all the time!! >:)
 
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