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Author
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Topic: 14mm Spark Plug advice?????
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n2oMike
Gearhead Posts: 3058
From: Spencer, WV
Registered: Jan 2001
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posted 07-15-2005 04:18 PM
 
The new engine is sitting between the fenders, and the headers are on. Now I need to buy and install some spark plugs!The last engine had the 289 heads, which used the 18mm plugs. I used Autolite 33's in those, which is a racing plug. I could have used the Autolite 32, but the insulator came all the way down to the bottom of the threads! Those were WAY cold! The 33's were perfect. Now I need to know what to use with these Trick Flow Twisted Wedge heads. They use common 14mm 3/4" reach plugs. They can use either gasket or tapered seat types. What is a good plug to use? Side gap would be fine. Thanks! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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steve'66
Gearhead Posts: 9835
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 07-15-2005 04:45 PM
AR-3923 IIRC  SteveW
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Dave_C
Gearhead Posts: 1123
From: Gadsden, Al
Registered: Aug 99
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posted 07-15-2005 04:48 PM
Mike,Take a look at the Autolite AR 3934 racing plug. They make from AR 3931 (cold) through AR 3935 (hot). Very good plugs. They are 14mm, .750" reach. For me, I can get them for less than $2 locally. O'Reilly's keeps them in stock and Advance Auto Parts has them on the PDQ next day order program. BTW, I use the colder AR 3932 and AR 3933 in my alky fed 557 bbf. David Cole ------------------
557 BBF Powered, alcohol injected rear engine dragster. 4.90 @ 143 1/8 mile. 1.09 60'. I've got to be crazy to drive this thing.
SC/ET #2729
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n2oMike
Gearhead Posts: 3058
From: Spencer, WV
Registered: Jan 2001
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posted 07-15-2005 05:13 PM
Thanks for the replies, guys!What is the difference between the AR-3923 and the AR-3933? Is one a side gapped unit? Thanks again! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220 [This message has been edited by n2oMike (edited 07-15-2005).]
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n2oMike
Gearhead Posts: 3058
From: Spencer, WV
Registered: Jan 2001
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posted 07-15-2005 05:52 PM
It looks like the AR3923 is a projected tip racing plug. The AR3933 is a non-projected tip.Autolite's web site states that an EVEN number in the third digit indicates a resistor type plug, and one less is the non-resistor version of that type. Using this bit of info, an AR3913 would be the non-resistor version of the AR3923. The AR3933 would be a different type of plug. Summit's website lists the AR3923 as a projected tip. The AR3933 is not listed as a projected tip. I didn't see a AR3913 listed, but they had a AR3911, which would be the same thing, only colder. SO..... is the AR3923 a projected tip version of the AR3933? And, should I use a projected tip or a non-projected tip for nitrous... I'm guessing a non-projected tip. It looks like I'm in the market for the AR3933.... An AR3923 looks like a good plug for a naturally aspirated, hotrod. Is all this correct???? Sorry for the 'thinking out loud' rambling. Thanks! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220 [This message has been edited by n2oMike (edited 07-15-2005).]
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mizry
Journeyman Posts: 97
From: ca
Registered: Sep 2004
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posted 07-15-2005 10:42 PM
Ive installed the 3923's in both 302's and now a 289 with domed pistons. they do have a projected tip and may cause piston contact if the piston dome hasent been clearanced. old school probe pistons are in the 289 and they came clearnced for a projected tip plug, im sure it gave up compression but I would rather just install the plugs rather than index them. And the 3923's are common at most parts stores for less than $10 a set. Oh yea I working on a big boost -20psi- 302 that came ready to go from bennet racing with the 3923 installed....... [This message has been edited by mizry (edited 07-15-2005).]
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steve'66
Gearhead Posts: 9835
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 07-15-2005 11:24 PM
Mike,To be truthfull I've only run the 3923 and 3924 Autolite plugs. They work fine, but I haven't special ordered the AR3923 or AR3924s yet. AR's are the racing plug, but the regular plugs have worked out pretty good for us. Just get a set of 3924's for your break-in and go from there.  SteveW
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