spark plug gap

prkaye · #1 10-13-2010, 10:02 AM

I couldn't find any specification of correct spark-plug gap in my engine manual. Where is this specified?
I have aviation spark plugs on my mag, and automotive spark plugs on my lightspeed... what gap value should I use for each of these? (O-320-D2A)

TX7A · #2 10-13-2010, 10:16 AM

Phil,
Here's a thread on the L/S Denso plugs if that is what you have.
http://www.vansairforce.com/communit...ad.php?t=13254
Post # 14 may have info for you. Double check other sources, though.

Edit:
The following is right out of the Lightspeed Manual (section 2.6):

Engines normally timed at 25 degrees BTDC:
These are normally engines with compression ratios less than 8.7:1. Gap spark plugs fired by the CDI to .032"-.040".

Engines normally timed at 20 degrees BTDC:
These are usually engines with compression ratios of 8.7:1 or higher. Gap spark plugs fired by the CDI to .026"-.035".

Turbo / Supercharged engines should gap the spark plugs to .026” - .035” while turbo normalized engines should gap the spark plugs according to the compression ratio.

prkaye · #3 10-13-2010, 10:27 AM

Thanks Sam!
What about the aviation plugs? Will that info be in my magneto documentation?

TX7A · #4 10-13-2010, 11:09 AM

Phil,
Someone will need chime in on the aviation plugs. I think it depends on the variety you have, etc.
Maybe check with your engine builder...? Sorry I couldn't be of help on that. I'm just not 'there' yet.

vic syracuse · #5 10-13-2010, 11:20 AM

Set your avaiation plugs at .016.

Vic

TX7A · #6 10-13-2010, 12:00 PM

Vic

Does that .016 also apply to an O-360?
Thanks

vic syracuse · #7 10-13-2010, 02:08 PM

Yes. That works for that one, too.

Vic