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What is the safe plug to default?

Performance mods and Advanced Stroker discussion.
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DaemonForce
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What is the safe plug to default?

Post by DaemonForce » March 22nd, 2019, 5:49 pm

I'm having issues with my 4.7L when starting. At the moment, both of my spark plug sets Champion 7034 and RC12LYC are fouled so bad that they will not spark. A few seconds of hard cranking will result in a backfire or ping which tells me the compression is high enough for this to autoignite. Rather than doing the stupid thing and trying to get this running with the same plugs, I'd rather hear the input from others that built a similar spec. Poor man's stroker recipe, injection system equal to a 96 Cherokee. The heat rating on these plugs (12) seems to go back as far as 1941. Is there something I did in this build that upset this assembly so much that I need to go to a colder plug? What is the safest plug to use in a new build?
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SkylinesSuck
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Re: What is the safe plug to default?

Post by SkylinesSuck » March 22nd, 2019, 7:29 pm

Sure your dizzy isn't off a tooth?

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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
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Location: Olympia, WA
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Re: What is the safe plug to default?

Post by DaemonForce » March 22nd, 2019, 7:42 pm

At the moment it could be but I don't have a way of confirming that now. I'm sure I will sort it out the next time I get this engine started but then I'm likely to run into fouling very quickly. That's the difficult part that I still need to sort out.
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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Cheromaniac
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Re: What is the safe plug to default?

Post by Cheromaniac » March 23rd, 2019, 2:04 am

You shouldn't be having issues with RC12LYC plugs on a poor man's stroker. I ran those plugs for 12+ years.
Either the timing set is one tooth off or the distributor is one tooth off.
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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: What is the safe plug to default?

Post by DaemonForce » March 31st, 2019, 7:19 pm

I'm running a mild Crower 44243 cam clocked -2°from default. I had issues with the distributor before but I'm sure it's fixed now. I just need to figure out what causes this carbon foul issue. I'm running Bosch 703 injectors@55psi. When I look up a comparison chart, it looks like my plugs are way too cold. But that couldn't be the case on a high compression stroker, right? Something seems really off.
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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The Beast
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Re: What is the safe plug to default?

Post by The Beast » April 4th, 2019, 8:19 pm

Maybe a little too much fuel with a weak coil? What do the plugs look like? Do you get a blue or orange spark at the wire?
My Jeep is like having a conversation with two lions, in both my ears, inside my head, from the outside.... I hear good things from them!

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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: What is the safe plug to default?

Post by DaemonForce » April 6th, 2019, 11:23 am

I'm using one of the yellow Accel coils. There is NO excuse for this to happen. I put the coil on a bench test power supply and so far all the plugs are firing off nice and blue. I went with a set of NGK 2262(ZFR5F-11) and I will be testing these new plugs later today. It's just a bear to set them up right now because I still need to bolt up my air compressor and water pump pulley. I'm expecting good results.
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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The Beast
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Posts: 39
Joined: October 12th, 2011, 2:00 pm
Stroker Displacement: 4.7
Vehicle Year: 1988
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Guelph ON Canada

Re: What is the safe plug to default?

Post by The Beast » April 6th, 2019, 8:51 pm

Hmm, it's hard to say. But definitely triple check that timing, I'd go over everything again just to make sure.
Plugs/coils can F off on ya without a reason too. I had a set of plugs just stop working not long ago lol.
My Jeep is like having a conversation with two lions, in both my ears, inside my head, from the outside.... I hear good things from them!

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