What's the Right Spark Plug Gap for a 350 Chevy?

Technical Discussions
1

I’m currently working on maintaining my 350 Chevy and I keep hearing different opinions on what the spark plug gap should be. I want to make sure I’m setting it correctly for optimum performance.

Could someone share their experience or knowledge on this?

  • Is there a recommended gap size for stock applications?
  • What about for high-performance setups?

I’ve seen figures ranging from .035 to .045, but I want to ensure I’m not missing anything crucial. Any advice or tips would be greatly appreciated!

Thanks!

2

For most 350 Chevy engines from the late 1960s to early 1970s, the ideal spark plug gap is typically .035 inches. This can vary slightly based on specific mods or factory specs, so always check your manual!

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3

That’s great info! I have a 1978 model and I’ve been confused about the gap. What do you suggest for that year?

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4

For the 1978 350 Chevy, the recommended gap is .045 inches. It’s great for emissions systems included in that model year.

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5

That’s a bit wider than I thought! Is there a performance difference if I adjust it?

6

Adjusting the gap can improve performance, but keep it within manufacturer specs to avoid misfiring or poor idling. For racing, you might go narrower, like .035, but it depends on your setup!

7

I had no idea spark plug gaps could have such an impact! So, if I boost my engine’s power, I should consider changing the gap too?

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8

Absolutely! A tighter gap can help with increased cylinder pressure, but ensure your ignition can support it. Might be a fun experiment!

9

It’s also essential to check if your ignition system can handle the adjustments. Don’t want to blow a fuse while experimenting!

10

My 350 is a 1990 model. Any difference in the gap recommendations for that year?

11

For the 1990 model, you generally stick with a .045 gap. It’s what the factory recommends to balance performance and emissions control.

12

Thanks for clarifying! I wonder if that’s also true for models with aftermarket chips?

13

Aftermarket chips can change the game! Depending on how aggressive the tune is, the gap might need adjusting to avoid pre-ignition.

14

I used to think sparks were only for starting my BBQ! Who knew gaps mattered so much? I’m definitely learning here.

15

Haha, that’s hilarious! But seriously, your engine’s performance can significantly benefit from the right gap!

16

This is all so helpful! I love that we can share this info. For a modded 350, what’s a good starter gap?

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17

If you’re modding, start with .035 inches and test. You might find you prefer something tighter or wider based on your setup and how you drive!

18

Hey everyone! I’m looking for the right spark plug gap for my 350 Chevy. I’ve heard that an incorrect gap can lead to issues like misfiring. Any insights?

19

Absolutely! A gap that’s too wide can cause a weak spark, while a gap that’s too narrow can lead to misfires. Generally, around 0.035-0.045 inches is recommended for a 350 Chevy.

20

Hi stevenskim! I just went through this with my 350. Make sure to check the condition of the plugs too. Sometimes, they can wear down and affect the gap over time, causing reduced power output.