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Buick spark plugs

losh1971

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I don't understand how 90% of cars run fine with 1.1mm and these old things with DFI which is higher power need the extra gap????
I've measured the gaps on these plugs and they are preset to 1.5mm. Surely other engines run these plugs and have the Bosch factory gap?
 

shane_3800

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I've measured the gaps on these plugs and they are preset to 1.5mm. Surely other engines run these plugs and have the Bosch factory gap?
Nope. They're GM plugs for the old DFI.
 

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Extra gap? Stock gap on these engines is 1.5mm Run a smaller gap if you run boost and you are loosing spark otherwise the stock spark plug gap is just fine.

On my old 3800 V6 I ran a smaller plug gap initially (as my suppliers book said 1.3mm instead of 1.5mm) and lost fuel economy. Bigger gap produces a hotter spark and burns and gives a better burn. I took a set of original AC delco plugs from a VN that were heavily worn, the biggest gap I measured was 1.7mm and the engine was still running fine, no miss. These 3800 V6 engines are low compression and can easily handle the the recommended 1.5mm plug gap.

The V6 engines have used the same ignition setup from late 1990 to the last of the VY ecotec engines (?2004). Only the first of the VN's had a slightly different DFI module and ignition coil pack that had a smaller 1.3mm recommended plug gap and from personal experience these too ran better with the 1.5mm gap.
 

shane_3800

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With coils the longer the gap the more KV it forces the coil to release. The higher the KV the hotter the plasma across the gap.
 

shane_3800

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Extra gap? Stock gap on these engines is 1.5mm Run a smaller gap if you run boost and you are loosing spark otherwise the stock spark plug gap is just fine.

On my old 3800 V6 I ran a smaller plug gap initially (as my suppliers book said 1.3mm instead of 1.5mm) and lost fuel economy. Bigger gap produces a hotter spark and burns and gives a better burn. I took a set of original AC delco plugs from a VN that were heavily worn, the biggest gap I measured was 1.7mm and the engine was still running fine, no miss. These 3800 V6 engines are low compression and can easily handle the the recommended 1.5mm plug gap.
Yea but I can't see how an engine needs over 20kv for street duties. I can't see how these engines get better economy when the chambers are like a old buick V8.
 

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Bigger gap = hotter spark = better burn.

GM/Holden set the plug gap at 1.5mm, clearly they did that for a reason. If you don't like that then you best contact Holden/GM and tell them they got it wrong.
 

losh1971

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I've been running Gorst coils, although I'm down to two Gorst and one other brand, as one of the coils arced out and burnt the post off. The Gorst provide an even bigger spark than the Delphi ones.
 

vc commodore

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So 1.1mm is no good?

On page 2, you were adminant the gap was .9 and 1.1 was too much.....Now you are saying 1.1 is the ideal gapping....

Might be best you not suggest a gap, because it is showing you don't really know and just throwing it out just because you can
 

shane_3800

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Bigger gap = hotter spark = better burn.

GM/Holden set the plug gap at 1.5mm, clearly they did that for a reason. If you don't like that then you best contact Holden/GM and tell them they got it wrong.

Yes but too much of a gap is actually a bad thing. 1.5mm is obviously fine. But 2mm would be excessive. Why do you think drag cars go for amps and duration to increase heat? Because a long spark will make a long initial flame front which can collide against it's self and cause knock. The Mercedes and Chrysler dual spark time their events via spacing so don't suffer from this.

But my whole point has been that the longer the gap the hotter the spark yes but the hotter the spark the more wear on the plug. This is why most standard plugs are .9mm to 1mm and iridiums are are 1.1mm in like 90% of cars. Seeing as a buick V6 has an ancient 60's design head I can't understand why it would benefit going from 1mm to 1.5mm.
You say you get better economy so maybe that is true I have not tested this so I can't comment on that.
But it seems the plugs losh has are nearly out of stock so you have the option of iridium or standard tungsten.

I was just suggesting changing the gap to try and improve wear on the plugs.
 

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The standard plugs last 40k. If you go through a platinum plug in 12 months you're using the wrong plug. Use the SCA USA ones but gap them back to .9mm and see how they last I bet they're 1.1mm gapped which is too much gap on a waste spark engine.

Bit of a memory refresher
 
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