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Which Spark Plugs?

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Old 02-18-2007, 09:10 PM   #1
Sky65
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Default Which Spark Plugs?

My car is a 65 but I have a 69 350 engine. I was looking at the AC Delco web site and looked for spark plugs by model. A 66 Corvette, doesn't have 65, 327 calls for R45S. A 69 350 Corvette calls for R43S. So. Which plug do I use? I would think the R43S to match the engine. However. I looked the C3 section and the recommended plug there seems to be the R45? Thoughts?
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Old 02-18-2007, 09:14 PM   #2
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Originally Posted by Sky65 View Post
My car is a 65 but I have a 69 350 engine. I was looking at the AC Delco web site and looked for spark plugs by model. A 66 Corvette, doesn't have 65, 327 calls for R45S. A 69 350 Corvette calls for R43S. So. Which plug do I use? I would think the R43S to match the engine. However. I looked the C3 section and the recommended plug there seems to be the R45? Thoughts?


R45 or R45S or equivalent in another brand.
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Old 02-18-2007, 10:15 PM   #3
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Old 02-18-2007, 10:22 PM   #4
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Quote:
Originally Posted by Sky65 View Post
My car is a 65 but I have a 69 350 engine. I was looking at the AC Delco web site and looked for spark plugs by model. A 66 Corvette, doesn't have 65, 327 calls for R45S. A 69 350 Corvette calls for R43S. So. Which plug do I use? I would think the R43S to match the engine. However. I looked the C3 section and the recommended plug there seems to be the R45? Thoughts?
The original plug for Corvette 327s through '68 was the AC 44. In 1969, it was the R44. The 44 series is not available anymore, but no matter as it was really a bit too cold for normal driving. The 45 series is better.

There is no real performance difference in the 45 or R45. The R is for resistor plugs which help reduce ignition noise in radios. The R45S has an extended tip which helps keep it cleaner from fouling and so it runs a bit better. However, if you have high domed pistons or the heads have been shaved, you could hit. You need to install the plugs, turn the engine over, and then check the plugs if you have any performance work done on the engine.

If you are running the R43S, you'd better be doing hot laps most of the day, because it is far too cold for the street.
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Old 02-18-2007, 10:59 PM   #5
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The original setup used nonresistor 44 plugs with resistor wires. If you use resistor plugs such as R45, and you have the original Delco coil, IMO switch to nonresistor wires or bag the original and expensive coil.

The original coil is easily overloaded by resistor plugs used in conjunction with resistor wires. So was the Pertronix Flamethrower thatI replaced it with - that lasted about a year before melting down.
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Old 02-18-2007, 11:08 PM   #6
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I am using an MSD distributor, 8.5 mil wires, blaster coil and 6al box so I need the resistor plugs. R45S or equivalent it is.
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Old 02-22-2007, 12:58 PM   #7
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NGK B4's
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Old 02-23-2007, 08:34 AM   #8
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I agree with Joe. The NGK B-4 is the same heat range as the AC 45 (hard to find) and is non-resistor and non-extended tip.

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