Using Denso plugs and having trouble finding documentation for plug gap.  I think it is .016.  Verification appreciated.

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Hi David, my Azalea Aviation manual indicates AC Delco plugs AC 44F with a plug gag of 0.035”.  Your distributor point gap should be set at 0.029 when we and when it reaches 0.016 should be serviced.  Fuel should only be 100LL.  If you want more specs and a torque chart I’ll be happy to share with you via your email address.

John Minatelli

To get a good answer you need to specify what conversion (William Wynne, Azelea, maybe this is a home-made conversion?) you are using and what type of ignition you have. The stronger the ignition the larger the plug gap is set. Magnetos (weak power of spark) use gaps around .016 - that would be most certified engines and some conversion engines. Coil and breaker point ignitions use around .035 gap (stronger power, can jump a bigger gap and make a more vigerous spark) while modern electronic ignitions use spark plug gaps as large as .060 (very powerful electrical charge so jumps a huge gap and makes a very potent spark).

Do you have a manual for your engine? If not you should get one.

Updated info- Using Denso plugs .030.

Of course you are right.  I have an Azalea Aviation 120 HP Corvair conversion engine with points and electronic ignition running off of a dpdt selector switch and redundant coils for each ignition choice.  The electronic ignition is a FAST XRi unit.  Point gap is 0.019, static point timing is 10 degrees BTDC number one cylinder.  Plugs are AC/Delco 44F with a 0.32 plug gap. Engine is carbonated with a 40mm Revmaster slide carb. The combination provides excellent performance.  The distributor is supplied by Azalea and tested at full speed to ensure a 28-32 degree BTDC advance at 2600 rpm.  This is the total advance eg. 32 total with 10 degrees static included in that total 32 degrees.  Do not exceed 32 degrees on the engine or you will get damaging detonation and I recommend you only use 100 LL.  How’s that?

John Minatelli

Which Denso plug # are you using?  Why Denso Vs AC Delco?    

I'm using Denso Iridium 5379/IWF-24 in my 3000 cc Corvair.  Other displacements use different plugs.  Reduces chance of detonation.  If you are either flying or contemplating flying behind a Corvair engine you should read WW's  new Maintenance, Operations, and Procedures Manual.  Standardized info all in one place.  Available from  Well worth the money.


Did you compare CHTs to previous plugs ? Any cooler ? 

 I have a 3.1. Using AC 44f 

  Was contemplating out of curiosity trying the Denso.   You mention a different plug for different displacements.   Whys that. 

I thought all corvairs used same plugs regardless of size. 


David B.,

The correct plug for your 3000cc corvair is the Denso IWF-22 gapped to 0.035.


What's the difference compared to what he's currently using as per WW  Mop? 

The IWF-22 is the recommended plug for the 3000cc as indicated in the MOP manual.  The IWF-24 that David mentioned above is the recommended plug for the 3300cc corvair.

The difference in the plugs is how hot they run and the ability to prevent lead fouling and detonation.  With Denso plugs the higher the number the cooler the plug.


Oops, I was wrong it is the IWF-22 gapped to .035.  Thanks Ken for pointing out my error.


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