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Tune Up Questions
 Pelicans, I putting in a new rotor, cap and plugs today. My car is a 79SC and has the 6420 MSD box installed by PO. Stock as far as I know. The old plugs were Bosch WR5DC gapped at .032. I ordered Bosch WR8DC from our host. My research says the new plugs because of the MSD box should be gapped at 1.27mm to 1.49mm. (If my conversion to inches is correct), that translates to .050 to .058 in. Also, the WR8DC are a hotter plug-correct? Is that going to be an issue or not? This forum is great!! Thanks in advance Kip
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02-11-2021, 10:45 AM
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How Bout You Big Boyz??? AL, Walt, Glenn. No one else thought this important, but it is to me. Such a simple question eh?
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02-11-2021, 04:38 PM
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Disclaimer - I don't have an MSD ignition but have certainly researched it (may be a future upgrade). A few questions:
- Which engine in your SC? 3.0 with all stock setup? If so, then I think the WR8DC is the current stock plug. Not sure why somebody was running 3 heat ranges cooler unless they were running a lot more advance or something. Where is your timing set? - Which coil are you running with the MSD box? Generic guidance from MSD does state 0.050-0.060 gap for a starting point for engines with 10.5:1 or less compression. |
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02-11-2021, 08:20 PM
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tune up questions
Fanaudical, thank you for the reply! It's a 3.0L, believed to be stock., so 8.5 compression ratio. The coil that's on it is a Bosch #0221119027 blue coil. I haven't checked ignition timing yet, but will do so after plugs, cap and rotor are installed.
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02-12-2021, 06:52 AM
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You might investigate a different coil. Here's an older thread where this was discussed; it seems a matched MSD coil might be a better option.
Can I use a Bosch "red" or "blue" coil? With the blue coil, you might start with stock gap and slowly open that a bit (.005" increments). Some other threads point to running less than 0.050" gap with MSD. |
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02-13-2021, 07:04 AM
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there should not be WR8DC but W8DC, not with the resistor...
Ivan
__________________
1985 911 with original 501 645 miles...807 319 km "The difference between genius and stupidity is that, genius has its limits". Albert Einstein. |
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02-14-2021, 01:09 AM
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Ivan, thanks for chiming in! When I ordered the tune up parts for my 79SC 3.0L from our host the web page said WR8DC were the plugs that were shown for my car. I didn't talk to parts and assumed the web page was correct... Am I missing something here??
Kip |
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02-14-2021, 09:47 AM
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yup ,it seams they do not make those any longer.
Bosch Spark Plug W8DC - Each Supersceded to WR8DC+ it is what it is Ivan
__________________
1985 911 with original 501 645 miles...807 319 km "The difference between genius and stupidity is that, genius has its limits". Albert Einstein. |
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02-14-2021, 10:35 AM
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Guess I'll do my due diligence next time. Thanks to those that offered feedback. It was appreciated!!
Kip |
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02-14-2021, 12:18 PM
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