Doing Plug Cuts

[XfireZ51]

So while waiting for the top end to come back from the paint shop, "idle hands are the blah blah blah...". Decided to replace spark plugs and while I was at it do some plug cuts. Plug cuts are where you remove the threaded collar of the plug to reveal the lower part of the ceramic insulation. This is what you do to tell what is really going on in the AFR department. As rpm and load increase, the burn characteristics of the AFR moves down towards the bottom of the insulation casing.

Here's what I found:

http://i187.photobucket.com/albums/x198/Z51Xfire/IMG_0084.jpg

http://i187.photobucket.com/albums/x198/Z51Xfire/IMG_0086.jpg

http://i187.photobucket.com/albums/x198/Z51Xfire/IMG_0085.jpg


Also, looking at the #2 cylinder, I found the primary valve perfectly clean
while the secondary and most of the other valves had the expected carbon build up on the back face of the valve.

http://i187.photobucket.com/albums/x198/Z51Xfire/Valvepics008.jpg

http://i187.photobucket.com/albums/x198/Z51Xfire/Valvepics007.jpg

Injectors??

[Paul Workman]

It appears #2 & 4 are running rich? And, #7 looks to be lean, no?

Hmmmmm.... when were the injectors last replaced???

P.

[FU]

Sure look's like injectors. Get them flow tested while it's still apart.

[GOLDCYLON]

Got to be the injectors. What brand are they?

[HAWAIIZR-1]

Great stuff Dom. Thanks for sharing and very interesting information.

[XfireZ51]

Guys,

The injectors are Accels. The pattern of clean primary valve is pretty consistent throughout the other cylinders. I think it demonstrates the diff between injectors being on constantly and turning On/Off. My secondaries come on
w >1.17% TPS. Suggests that the carboning may be due primarily to idle.
I decided to swap the secondary injectors between 1-2, and 7-4.
See if it balances things out. Likely get motor together and head to dyno.
Then pull plugs again on those cylinders and see.