Question about OE spark plug gapping on 5vz-fe

The OE Densos are supposed to come pre-gapped, but they never do, or so everyone says.

I got them. Here's the thing:

The edge of the electrode is not flat, it's concave. I used the cheap gapper from Autozone. But it's measuring the edges and not the trough. They are the contact point when you slide the gapper through.

I widened the gap, but now I'm wondering if the trough, bowl, or deep part of the concave edge wasn't already gapped properly, and by measuring from the edges, I've widened them too far.

Do you understand my question. The reason I ask, is they were all gapped the same. And the amount I opened them is about the difference between the edges and the trough.

 

see how they are curved? they curve around the center electrode. so are the edges supposed to be .043 away, or the interiror of the curved part (which is away then the edges? It may not seem like much, but these amounts mean a lot on a plug. a basic gapper only lets you set the edges.

 

Read at the Denso site that you need to get a "feeler gauge" to properly gap them. Great! Does Denso sell that too? (sarcasm)

Looked on-line and only found ones that go up to .040 and then ones that begin at .050.

I'll have to call around the auto parts stores tomorrow and see if someone has one. I asked at the Autozone nearby and the sales associate looked at me like I was speaking Chinese. I don't know why they couldn't understand, since everything in the store is made in China and marked with Chinese lettering.

 

I thought this would have been a relevant discussion, what with all the posts I read about how the plugs don't actually come pre-gapped. No matter, maybe my solo thread will help someone like me in the future. Here is what I found:

THEY COME PRE-GAPPED!

I called around to pretty much every auto parts store in Sacramento to find the wire type feeler gauge to properly gap these. Most people I spoke to had no clue what I was talking about, though that's usually the case even if your asking for motor oil.

With the proper type of gauge, I checked the plugs that I had originally 'corrected' with a standard gapper and as I suspected they were loosey-goosey. They were also a bitch to try to narrow.

So, I went back to the dealership and got 6 new ones. And when I checked them with the proper gauge, THEY WERE ALL IN SPEC!

THEY COME PRE-GAPPED!!

Yes, there were a few that were either slightly wide or narrow, but the amount was very negligible. You can take them out of the box and bolt them in as is.

So, my conclusion is that those who claim these plugs are not pre-gapped may just be using the wrong type of gauge. Maybe not, but the wrong gauge will give you a false reading. It did for me.

 

Post a picture of how you are checking the gap and what measuring tool you are using so we can follow your description better . Gotta do my plugs this weekend and was planning on using a feeler guage . I beleive I have every spark plug gapper that was ever made . Electricity always takes the shortest path .
Interersting post !!! I have a 2nd gen with 4 litre and will post my findings as well

 

Here's a right, left reference. In the left, I used the corresponding gauge and corrected the gap, arriving at .043. In the right, I used the corresponding gauge and found no correction needed, also arriving at .043. The final pic shows a comparison of the two.

 

And if you look at my pic in post #2, you'll see the patented Denso u-groove electrode. It's curved, which means that each point on the surface of the electrode is equal-distance from the CENTER of the center electrode. It's curving around the center.

If you use a standard flat wedge style gapper, you are actually checking/changing the distance between the outer edges of the u-groove electrode and a tangent off the circumference of the center electrode. Then, in that case, all the points on the curved surface are no longer equal distance from the center of the center electrode.

If they were standard plugs, this wouldn't be a problem, since the single electrode usually bends over the top of the center electrode. Both edges are flat in that case.
But since denso wants an electrode that flanks the center pin, they decided to curve it's edge to match the rounded edge of the center pin.