1916 DB spark plugs

[vergil]

I sm replacing Champion c-4's. I have Champion 518 W18 plugs to install. Am I correct? The repair manual suggests .030" gap. I just don't want to make a mistake.

[nearchoclatetown]

That's what I use in my '24 and it seems happy.

[vergil]

Thanks again! You are a most helpful enthusiast!

[mlander]

Go to;

http://www.sparkplugs.com/results_cross.asp?pid=C4&x=61&y=15&seenCrossWarning=1

The above gives the address of the distributor of many brands of sparkplugs.

Their callout for the sparkplug of a new replacement Champion sparkplug as a, W 16Y, 7/8” -18 threads per inch, with a reach of 5/8 inch, 15/16” hexagon, Standard Coil Stock # 561 , Industrial sparkplug. This sparkplug does have a nominal 5/8" reach and an extended core nose of about .170".

The reach of a sparkplug is the nominal distance from the gasket seat of the sparkplug without the gasket in place to the end of the sparkplug threads. Notice this removes the sparkplug gasket crushed thickness from the dimension! It also does not include the provision of an extended skirt as is evident on some sparkplugs.

Altho a very belated post it is in hope of a better understanding of sparkplug terminology!

M.L. Anderson

[Guest Jack27]

I always used C-4 s in my 16 for 30+ years. If you have a magneto the 0.031" gap will make it hard to start when temp is low. The '16 owners manual says 0.031" gap but other references say 0.016". I changed to 0.016" and car would start anytime. The '16 owners manual states 0.031" but must have reflected going to a distributor ignition (1917) which uses 0.031 gap.

[mlander]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jack27</div><div class="ubbcode-body">I always used C-4 s in my 16 for 30+ years. If you have a magneto the 0.031" gap will make it hard to start when temp is low. The '16 owners manual says 0.031" gap but other references say 0.016". I changed to 0.016" and car would start anytime. The '16 owners manual states 0.031" but must have reflected going to a distributor ignition (1917) which uses 0.031 gap. </div></div>

I knew there was a good reason for the use of Capacitors/ Distributors but this is the first time anyone expressed it so succinctly. Magnetos certainly have their place but their innate faults certainly put them behind the Delco with its centrifugal advance and later the vacuum advance.

M.L. Anderson

[Guest Jack27]

If your car has a magneto the plug gap should be 0.016" . The '16 owners manual specifies 0.031" but this is for a distributor ignition. In cold weeather the engine does not crank fast enough for the magneto to get a enough spark at a 0.031" setting.