• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Spark plug gap

Share this page

B

billspit

Jedi Knight
Country flag
Offline
Yesterday I was installing new Champion plugs in the 80 Spitfire engine I have rebuilt. The book says the gap should be 0.025". Its been a long time since I've installed plugs in one of these engines, but is that correct? Seems like everything now is 0.040" or so.
 
.025" is correct, at least for points ignitions. Larger gaps are common nowadays with electronic ignitions, and it's possible that your '80 Spitfire (presumably equipped with some sort of electronic ignition) might benefit from a gap somewhat larger than the old .025"?
 
Once I get the engine broken in, I will be going with a Pertronix ignition. It orginally had the electronic ignition that all late Spits had.
 
to go to the big gaps, you need a HOT coil and something like an MSD, Crane, etc.
Rob
 
No question,a larger gap is going to require either a coil with greater potential voltage output, 20k vs 40k OR increase dwell time for the coil to build voltage.
The draw back is that higher voltage will tend to carbonize the rotor and contacts in the dizzy cap or worse,so carry spares.
Although this article addresses Ballasted Ignition, there's something to be learned regarding the relationship between plug gap and coil potential.
https://www.vtr.org/maintain/ballast.shtml
 
Back
Top