Spark Plug Gap

[Eric Smit]

25 is not the correct gap, just FYI.


-Eric Smit

 

[ChrisJ]

On the subject of spark plug gap: Back in the mid 1970s GM specified a spark plug gap of .060 on some of their engines equipped with the then new HEI electronic ignition system. The reasoning was improved performance, better combustion, reduced emissions etc. The HEI system was capable of delivering in excess of 50,000 volts in the secondary ignition system. The coil was indeed capable of firing the wide gap plugs, but the problem was that the spark would jump the path of least resistance, which wasn't always the plug gap. Spark would discharge right through the spark plug wires and boots to nearby manifold heat shields, and sometimes the intense voltage would discharge right through the distributor rotor to the distributor shaft; drilling a hole through it and shutting down the engine. Opening the hood at night with the engine running would often provide a light show of sparks from the plug wires. The fix was to reduce the gap to a more modest .045
Todays modern engines with coil on plug technology, and no ignition distributors, have fewer problematic components, and are more reliable.

---------------
Papasonic

Heh I just got similar information from my dad who worked on a lot of cars in the 60s and 70s. He was talking about their 50,000 volt HEI systems and large gaps in the 70s

So I'm curious why the Sonic has such a small gap. So under pressure you need more voltage to fire the same gap (.028). Are the coils not capable of 50Kv on the Sonic? I would think a 50Kv system should have no issue firing those plugs at .045 even with boost. By capable I'm talking about being able to produce it reliably without breaking insulation down on the windings.

 

[Eric Smit]

It's not necessary.


-Eric Smit

 

[sonic hotness]

I Didnt have no torx at all need to buy some new tools

Iam guessing its a t30

 

[$ub$onic]

Its a 40 or 45 I forget I just called them today

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[sonic hotness]

Gonna check the gap Tom row morning, was hoping my bov came in all ready since iam on vacation this week.

 

[sonic hotness]

T30



Oh man were they off

.20
.23
.21
.23

I did have a little ruff start up with the gaps like this and a little lag between shifts


I set them all to. 28


Car starts fine now i drive it later on and give a bit more of a update


This is a must check guys

 

[$ub$onic]

Wow that's like a average of 2-5 thou off

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[Bogus]

T30



Oh man were they off

.20
.23
.21
.23

I did have a little ruff start up with the gaps like this and a little lag between shifts


I set them all to. 28


Car starts fine now i drive it later on and give a bit more of a update


This is a must check guys

Try .035

 

[$ub$onic]

I've had good luck at 35

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[sonic hotness]

1.4t calls for .28

I could not believe how off of order they were

 

[Larry]

1.4t calls for .28

I could not believe how off of order they were

35 is better, but with the tune you might have spark blowout. If it feels better, leave it alone.

 

[Bogus]

1.4t calls for .28

I could not believe how off of order they were

Oh I forgot you have turbo. Yeah .028 max for you.

 

[sonic hotness]

Ya feels way better

 

[Bogus]

Now you can burn rubber.

 

[key1cc]

After pulling the plugs the first time and setting all at .028 ...............
I also documented the change with High Rez pictures from my new camera.

Did you ever post the pics?

Edit 11/16/12: never mind....i did
Key1

 

[Jeraime1741]

plug blowout real bad

Man i dont know whats going on....i checked and regapped the plugs at a service station....
Youll see at my previous posts....but i am still recieving ALOT of blowout.....what can i do to stop that.....i mean i was going to upgrade to full tune but i dont want to if its going to make it worse....hopefully with the logging it will be better but i would definetly like some insight on this....

 

[$ub$onic]

Then keep decreasing the gap till u Dont get any

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[Bogus]

What's ur gap at currently?

 

[key1cc]

what he said...

Key1