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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11739 Location: Redding, CA
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Posted: Wed Sep 19, 2018 10:51 am Post subject: Spark Plug Gap |
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For those with stock carbureted engines, what gap do you use on the spark plugs?
Bentley provides mixed messages, according to where you’re looking in the book. At one point, they tell you .024, at another point, they say .28.
I’ve always understood that the larger gap was for fuel injected engines, starting in 1975, but my original 1974 Owners Manual says my gap should be .028.
I’ve always gapped my plugs at .024. However, my 1600 dual port with a Bosch 034 distributor, coupled with a Volkzbitz-restored Solex 34 pict 3, has always given me plugs that have been a bit rich looking when I pull to change or replace them. I’ve never gotten that “tan-gray” perfection, but more like a gray electrode with a thin black layer in the cup.
The engine runs extremely well with lots of power, and I get 28 mpg on the highway.
My question is this: could my issue be the result of gapping my plugs at .024, instead of .028? Would the larger gap provide better combustion?
Take into account that my carburetor is adjusted properly. I use a tach when adjusting, and I do it exactly as Bentley, Haynes says to do it. My timing is also spot on at 7.5 BTDC. Advance is perfect.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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73SlowBug Samba Member
Joined: November 28, 2017 Posts: 439 Location: PENNSYLVANIA
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Posted: Wed Sep 19, 2018 11:23 am Post subject: Re: Spark Plug Gap |
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I use .32, with electronic ignition. Works great. No knock, better fuel economy. I was using .28 with points and condensor, and when I first switched to the points replacement device. The bosch plugs come pre gapped at .28. I Immediately noticed smoother delivery when I switched to .32. I haven't seen any adverse effects, and no plug fouling. I'd imagine your results would be similar going from .24 to .28 with points and condensor. I just pulled my plugs to replace last week, and they looked pretty good, but I'm replacing them yearly anyway. _________________ Daily driven....Slowly. |
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gt1953 Samba Member
Joined: May 08, 2002 Posts: 13843 Location: White Mountains Arizona
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Posted: Wed Sep 19, 2018 11:57 am Post subject: Re: Spark Plug Gap |
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Wider gap is the way to go. The smaller gap is great for starting when it is really cold. _________________ Volkswagen: We tune what we drive.
Numbers Matching VW's are getting harder to find. Source out the most Stock vehicle and keep that way. You will be glad you did.
72 type 1
72 Squareback
({59 Euro bug, 62, 63, 67, 68, 69, 73 type ones 68 & 69 type two, 68 Ghia all sold}) |
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Cusser Samba Member
Joined: October 02, 2006 Posts: 31271 Location: Hot Arizona
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Posted: Wed Sep 19, 2018 2:32 pm Post subject: Re: Spark Plug Gap |
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0.025 inch for me.
For both:
1600 DP 2016 rebuild with Solex 30/31 PICT carb and German 009 with points
1835 DP with single Weber 40DCNF and German 009 with points _________________ 1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297
Last edited by Cusser on Wed Sep 19, 2018 4:45 pm; edited 1 time in total |
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mukluk Samba Member
Joined: October 18, 2012 Posts: 6985 Location: Clyde, TX
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Lingwendil Samba Member
Joined: February 25, 2009 Posts: 3987 Location: Antioch, California, a block from the hood
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Bob Loblaw Samba Member
Joined: August 17, 2008 Posts: 865 Location: Vancouver Island, Canada
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Posted: Wed Sep 19, 2018 3:23 pm Post subject: Re: Spark Plug Gap |
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I learned to gap them at "a loose 0.028" _________________ sent from a phone using poor grammar and spelling |
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gt1953 Samba Member
Joined: May 08, 2002 Posts: 13843 Location: White Mountains Arizona
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Posted: Wed Sep 19, 2018 4:55 pm Post subject: Re: Spark Plug Gap |
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According the Without Guesswork manual...it says electrode gap .028 inches. That is what I have followed all of these years. _________________ Volkswagen: We tune what we drive.
Numbers Matching VW's are getting harder to find. Source out the most Stock vehicle and keep that way. You will be glad you did.
72 type 1
72 Squareback
({59 Euro bug, 62, 63, 67, 68, 69, 73 type ones 68 & 69 type two, 68 Ghia all sold}) |
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VW_Jimbo Samba Member
Joined: May 22, 2016 Posts: 9880 Location: Huntington Beach, CA
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Posted: Wed Sep 19, 2018 5:40 pm Post subject: Re: Spark Plug Gap |
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I set them at .028. No bigger, no smaller, no matter what engine I work on. The Bosch W8AC’s came preset at that spec. I would still check them but it was so nice to not have to bend the electrode. _________________ Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
TDCTDI wrote: |
Basically, a whole bunch of fuckery to achieve a look. |
67rustavenger wrote: |
GFY's Xevin and VW_Jimbo! |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11739 Location: Redding, CA
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Posted: Wed Sep 19, 2018 11:26 pm Post subject: Re: Spark Plug Gap |
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Thanks for the replies, folks. Next time I take out my plugs, I’ll gap them to .028 and see what happens.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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runamoc Samba Member
Joined: June 19, 2006 Posts: 5593 Location: 37.5N 77.1W
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Posted: Fri Sep 21, 2018 8:57 am Post subject: Re: Spark Plug Gap |
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Quote: |
I’ve never gotten that “tan-gray” perfection, but more like a gray electrode with a thin black layer in the cup. |
This is more of the plug's heat range than the gap. A spark plug is an electrical device. Certain characteristics 'help' the plug need less voltage to 'jump' the gap. One is for the center electrode to have square edges, not rounded. Platinum plugs have such a small diameter center electrode that having square edges doesn't matter so they need less voltage to make the 'jump'. The output voltage of the coil is what really determines how large a gap will work. _________________ Daily driver: '69 Baja owned 44 yrs - Plan B: '81 Rabbit Diesel LS Deluxe - Plan C: '72 Ghia
Yard Art: 2 Sandrails
Outback: '69 Ghia - '68,'69,'70,'72 Beetle - '84 Scirocco, GTI - Pair of '02 Golfs-
VW Wiring = It's just wires |
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Volks Wagen Samba Member
Joined: February 13, 2013 Posts: 2926 Location: Germany
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Posted: Fri Sep 21, 2018 1:02 pm Post subject: Re: Spark Plug Gap |
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Tim Donahoe wrote: |
However, my 1600 dual port with a Bosch 034 distributor, coupled with a Volkzbitz-restored Solex 34 pict 3, has always given me plugs that have been a bit rich looking when I pull to change or replace them. I’ve never gotten that “tan-gray” perfection, but more like a gray electrode with a thin black layer in the cup.
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Ah, the quest for perfection... Thin black layer - is it sooty? If you do a lot of tootling around town and idling u might get that anyway. Also short trips will mean you'll be running a bit rich at the start... If that's your general type of usage, then maybe getting a 'hotter' plug would be better.
If you take it out for a good blast before the next reading, get it up to temp and give it a bit of a run, then it might self clean a bit more. It's got the signs of being a little bit rich or a bit cold. _________________ 1973 1303 with AB-motor - sporadic
reconstruction as time permits, 1986 ex-Bundeswehr Doka - on the road again.
I'm definitely, probably, the worlds greatest lover.
Aithníonn ciaróg ciaróg eile. |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11739 Location: Redding, CA
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Posted: Fri Sep 21, 2018 1:29 pm Post subject: Re: Spark Plug Gap |
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Thanks, Volks.
Yes, the bug doesn’t get much highway driving. A few times a year, I’ll get it on a long freeway drive; but, for the most part, I’m just driving in town.
A hotter plug may be the way to go.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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