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Mon Aug 03, 2020 4:40 pm

Does anyone know where I can get a spark plug gap tool that measures .024?

All of them that I’ve seen so far have a .025 and on.

Tim

Mon Aug 03, 2020 4:44 pm

Easy enough to just use a standard set of feeler gauges versus trying to track down an oddball tool.

Mon Aug 03, 2020 4:46 pm

Not that i'm a fan of Harbor Freight, but this is the first one that came up.

https://www.harborfreight.com/feeler-gauge-32-pc-63665.html

0.0015 in. , 0.002 in. , 0.0025 in. , 0.003 in. , 0.004 in. , 0.005 in. , 0.006 in. , 0.007 in. , 0.008 in. , 0.009 in. , 0.010 in. (2), 0.011 in. , 0.012 in. , 0.013 in. , 0.014 in. , 0.015 in. , 0.016 in. , 0.017 in. , 0.018 in. , 0.019 in. , 0.020 in. , 0.021 in. , 0.022 in. , 0.023 in. , 0.024 in. , 0.025 in. , 0.026 in. , 0.028 in. , 0.030 in. , 0.032 in. , 0.035 in.

Mon Aug 03, 2020 5:04 pm

I was looking for a wire-type spark plug gapper, as opposed to the flat feeler gauges.

I’ve always used my wire feeler gauges that have the .025 as the first (smallest) size available. But it would be more accurate to adjust the electrode to .025, as my manuals suggest for carbureted models.

Tim

Mon Aug 03, 2020 5:15 pm

I think it matters as to how the maker of the tool wants to round off the numbers. I have three wire gappers, one of them, well, the 25 fell out and got lost. :cry: Another is 25, but my Bosch tool says 24, all of them say .6mm though, which is where the rounding thing comes in I think.

Mon Aug 03, 2020 5:54 pm

.025 is close enough

or, use a #73 wire drill

Mon Aug 03, 2020 7:02 pm

Given the VW is 99% metric .024" is just a close equivalent to .6mm, so that's what you're really looking for.

General specs are .6 to .7mm so you can go as large as .028" and still be okay. Wider will make a hotter spark and resist fowling as well.

In any case I've always figured as long as they're all the same a thousandth over or under won't matter much.

Mon Aug 03, 2020 8:00 pm

Yes, looks like the .025 is going to have to do.

Tim

Tue Aug 04, 2020 12:57 am

did you not want to pay $5 shipping for a 2$ drill bit?

Or was it the reality that sank in?

Tue Aug 04, 2020 6:52 am

Why have a narrow gap on the plugs?

Tue Aug 04, 2020 11:43 am

Why is .024 gap seem like a “narrow” gap? It’s exactly the size gap my Bentley says to use.

Tim

Tue Aug 04, 2020 1:38 pm

I've seen that Bentley specifies a 0.024" gap for spark plug in one area, but seems like they showed it as 0.028" in another area or chart of the book (IIRC -- ??). And most of the owners manuals and other literature I've seen (for early 70's bugs) usually seem to specify a 0.028" gap for the plugs. However, somewhere else I read that the 0.024" gap is supposed to help with starting in really cold weather (I think - ?).

In any case, think that you can use between 0.024" to 0.028" as you desire. I find that the latter value (0.028" gap) usually works best for me -- car seems to idle a tad smoother that way (although that may just be my imagination...).

Tue Aug 04, 2020 2:00 pm

From what I’ve been able to gather, the .024 was the gap for engines with carburetors, and the .28 was the gap for fuel-injected engines.

However, my Bentley says what I stated above, but my Owners Manual says to set the gap at .028.

I’ll just do what I’ve always done, and set the gap at the lowest wire on my gauge (.025). My whole point in starting the thread was to see if anyone knew where to find the .024 wire gauge. It’s a little picky thing, I guess, but ....

Tim

Tue Aug 04, 2020 2:38 pm

gt1953 wrote: Why have a narrow gap on the plugs?
While I agree that a larger gap with larger/longer spark is desirable, the spark plug gap needed is dependent on multiple variables:
the ignition system output voltage (higher voltage can jump larger gaps)
air-fuel mixture (rich mixtures are more difficult to ignite)
electrode material and design (fine tip iridium electrode; multi electrodes; etc.)
compression ratio (higher compression is harder to ignite)
combustion chamber design (placement of spark plug and shape of chamber)
contaminants (oil in the cylinder will hinder spark)
All of the above affect the distance the spark can jump between the electrodes. Except for the first few, most are out of our control on an assembled engine.

The meek VW ignition coil is only rated to output around 15,000v. So the gap must be kept in the 0.024"~0.028" range. Even if the stock coil could jump a larger gap at idle, when you get up to higher rpms there is less time (ms) for the coil to charge so the spark is weaker, so the gaps must remain small. This higher rpms timing is one of the reasons modern ignition system use a "coil-on-plug" arrangement to allow for more charge time. Also consider that many high milage ACVW engines leak a little oil into the cylinders. This makes it even harder for the spark to jump the spark plug gaps.

More modern HO coils can output as much as 45Kv or 60Kv. These can jump larger electrode gaps (0.035"~0.045"). Most of these coils require low resistance triggers (electronic modules) and will quickly burn mechanical points. Note that some race engines with crazy high compression ratios and rich air-fuel mixtures may require plug gaps as low as 0.015" even when running 60Kv ignitions!

If you really want to open the plug electrode gap you should be looking at capacitive discharge ignition (CDI) systems (eg. MSD or Mallory). These use the ignition coil as a pure voltage multiplier injecting as much as 300v into the primary windings of the coil. Many are multispark too which aid in complete combustion.

Wed Aug 05, 2020 9:05 am

ashman40 wrote: . . . If you really want to open the plug electrode gap you should be looking at capacitive discharge ignition (CDI) systems (eg. MSD or Mallory). These use the ignition coil as a pure voltage multiplier injecting as much as 300v into the primary windings of the coil. Many are multispark too which aid in complete combustion.
Don't forget my personal favorite, the Winterburn CDI. One of the best investments I ever made.

Wed Aug 05, 2020 9:24 am

I use .028" with a Bosch Blue.

Wed Aug 05, 2020 7:35 pm

Tim Donahoe wrote: Yes, looks like the .025 is going to have to do.

Tim

I'm a fan of whatever works best. For my Sun Bug, the new plugs were gapped at .025 to begin, but was running far too rich and after they were gapped to .028, it solved the issue. That worked for me and if .024 works for you, Tim, then I say do it. I have always found these gapper coins at the local hardware stores and I see that O'Reilly's sells them. Best of luck, Tim.

https://www.oreillyauto.com/detail/b/performance-t...&pos=5

Thu Aug 06, 2020 7:33 pm

Duane, so you’re saying that your rich condition was improved by gapping your plugs to .028?

That’s curious, since my engine has always run a bit too rich (in my opinion, anyway). When I change plugs, I’ll give your idea a try to see if doing so will lean it out a tad.

Tim

Thu Aug 06, 2020 8:01 pm

@Tim, not sure if you have taken a look at this tool...
https://www.summitracing.com/parts/mnp-08-0579

It has a specific 0.6mm gauge (go metric! :P ). If my math is correct, that works out to 0.0236".

Oh, and the large opening end is a bottle opener! :D

The other tool I found was a spark plug gapping plier.
https://autoplicity.com/292046-accel-spark-plug-gapping-pliers
But this seems only useful if you need to gap something like 20 plugs in one sitting.

They are also becoming a hard thing to find. I seem to recall my father having a similar Snap-On spark plug pliers. Here is a pic of one I found while Googling:

Fri Aug 07, 2020 7:11 pm

Tim Donahoe wrote: Duane, so you’re saying that your rich condition was improved by gapping your plugs to .028?

That’s curious, since my engine has always run a bit too rich (in my opinion, anyway). When I change plugs, I’ll give your idea a try to see if doing so will lean it out a tad.

Tim

Tim, yes, after the gaps were expanded from .025 to .028, my SB ran much better. Prior, it was running very rich.