Keep melting #1 cyl sparkplugs - Hemi Truck Club
 
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Old 05-24-2017, 10:26 AM   #1
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Keep melting #1 cyl sparkplugs

So I've been having an issue with melting the straps off the plugs in cyl #1. It's in a forged 349 vvt block running a return-style fuel system, ported heads, ported 6.1L intake manifold, and a F-1A at 17psi with a water/meth system. I run straight water on the street for cooling and it comes on at 5psi. I have a wideband on each bank and at part- and half-throttle AFR is typically between 12.8 and 14 with part throttle boost of 0-2psi; WOT is mid-11s.

Attached are pics of the plugs I pulled last winter before laying the truck up with a blown trans; the last two are the plugs I just pulled out after maybe 200kms, you can see the metal balling in the magnifying glass. There are missing insulators as well which really has me scratching my head.

I'm pulling the head today to check the piston just in case but I'm wondering if it's tune related since I've only had it tuned once since I haven't been able to keep it on the road long enough to get any miles on it. I have the throttle body rotated 90 degrees to fit the 6.1L intake manifold, possibly a contributing factor?
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File Type: jpg E87E093E-4D08-4E58-905C-C4CCF796DF14_zpsqaqnndlu.jpg (66.7 KB, 5 views)
File Type: jpg IMG_2051.jpg (29.8 KB, 5 views)
File Type: jpg IMG_2052.jpg (34.6 KB, 4 views)

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Old 05-24-2017, 10:34 AM   #2
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Too hot of a plug. What's your timing set to at 17psi boost?
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Old 05-24-2017, 10:37 AM   #3
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That's the classic look of detonation.. your afr is good. I'd look for a vacuum leak on #1, causing it to lean or a weak coil.
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Old 05-24-2017, 10:38 AM   #4
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Quote:
Originally Posted by CharonBlk07 View Post
I'm wondering if it's tune related since I've only had it tuned once since I haven't been able to keep it on the road long enough to get any miles on it.
I have the throttle body rotated 90 degrees to fit the 6.1L intake manifold, possibly a contributing factor?
Tune yes. TB no.
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Old 05-24-2017, 10:42 AM   #5
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Engine compression ratio? 9:1ish?
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Old 05-24-2017, 10:49 AM   #6
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Quote:
Originally Posted by Redtruck-VA View Post
That's the classic look of detonation.. your afr is good. I'd look for a vacuum leak on #1, causing it to lean or a weak coil.
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Old 05-24-2017, 11:24 AM   #7
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Quote:
Originally Posted by Ghost03hemi View Post
Too hot of a plug. What's your timing set to at 17psi boost?
6 degrees advance was all we could get into it during the initial tuning but it rarely sees over 12psi in daily driving. Plugs are Denso 3381s, think a colder plug could help? They've been gapped to .028" down from .030", since we thought I'd been having spark blowout issues with the higher boost.

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Originally Posted by Redtruck-VA View Post
That's the classic look of detonation.. your afr is good. I'd look for a vacuum leak on #1, causing it to lean or a weak coil.
I just replaced all 8 coils with new Mopar ones and I've done pressure and leakdown tests on all the cylinders and there's nothing special with #1. First set of plugs was the old coils, second set was with the new coils.

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Originally Posted by Ghost03hemi View Post
Engine compression ratio? 9:1ish?
9.5:1 with the thicker head gaskets.
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Old 05-24-2017, 12:09 PM   #8
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Protruding spark plugs are more susceptible to blow-out then recessed ones. I would try colder plug and limit the boost to say 6psi and slowly work back to see under what conditions it starts detonating.
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Old 05-24-2017, 12:18 PM   #9
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Once I get the 4L80 into it next month I'll throw my Brisk plugs in and see how it behaves, they're shrouded and 3 steps colder.
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Old 05-24-2017, 12:27 PM   #10
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Once I get the 4L80 into it next month I'll throw my Brisk plugs in and see how it behaves, they're shrouded and 3 steps colder.
Now you are talking. Exactly what I would do.
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Current 60' PB 1.351 (2019) mechanical issue for 1/4m

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