When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
"Every little bit counts when tuning for that last bit of available power. Using these spark plug indexing washers will allow you to face the open side of the electrode towards the fuel charge instead of it being masked by the grounding strap on the plug. Five each of three different thicknesses are included in 12 or 14mm size."
do these the things produce a measurable difference or is it just a drag strip "Best Practice"?
I bought some from Amazon. Used 0.060" washer on my rear plug.
It added at least 10 hp according to my butt dyno Couldn't see any difference in my PV logs, might make more difference if you are running more than 14.6 to 1 AFR Maybe just a little more "smoothness", placebo effect
I will keeping indexing new plugs though, gives me something else to tinker with.
do these the things produce a measurable difference or is it just a drag strip "Best Practice"?
Don't you have a Hammer 1275 kit?
Did you get 30 degree dome pistons?
I think Hammer sends the indexing washers with the 30 degree piston kits
From the Hammer instructions:
"SPARK PLUG WASHERS:
30 degree full dome pistons can sometimes try to hit the spark plugs. This may happen with the engine cold, or it may clear when cold and instead close up the plug gap after the motor is run for a bit. If you have 30 degree full dome pistons, it's important to check for this, and adjust the spark plug position for clearance using indexing washers. Complete engine packages that come with these pistons all include a package of indexing washers. If you have 30 degree full dome pistons and don't have a set of indexing washers, contact us and get a set before starting your motor....."
I think he has the Harley kit. I have put in several kits from Hammer and never got indexing washers from them. That includes the regular reverse dome and the 30 degree type..That may have been when they first came out with the reverse dome pistons.
Of course the 30 degree pistons I have now are matched to Hammer reworked heads and they would have taken care of any clearance problems. The problem may come with using stock heads.
Last edited by apache snow; Apr 8, 2018 at 07:00 PM.
I have index washers to keep the plugs from hitting the pistons on both my 1250/1275. So many theories as to which direction it goes if you’re indexing for the plug position itself. I took Aaron’s advice on which way to point the plugs. Had my 12 year old son do it. He enjoyed the process. I, on the other had have never indexed a sporty plug ever. If you’re looking for everything, sure , why not. Im my experience it takes a lot of everything’s to make a difference.
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Slideshow: The bar-and-shield logo shows up on far more than motorcycles, some of the company's most unexpected products have nothing to do with riding.
Slideshow: From the troubled AMF years to modern misfires, these bikes earned reputations for reliability issues, questionable engineering, or disappointing performance.
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Slideshow: The Swiss custom shop has taken a Harley Softail and stretched it into something so long and low that it looks closer to a rolling sculpture than a conventional motorcycle.
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Slideshow: A standard cruiser becomes an intricate metal canvas in the hands of a Swiss custom house known for pushing Harley-Davidson platforms far beyond their factory brief.
Slideshow: Harley-Davidson's challenges aren't abstract; they show up in dropping shipments, shrinking dealer traffic, and strategic decisions that aren't yet translating into growth.
Spark Plug Index Washers
Couldn't see any difference in my PV logs, might make more difference if you are running more than 14.6 to 1 AFR 
