Doing Plug Cuts - ZR-1 Net Registry Forums

XfireZ51 · 03-31-2012

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:

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.

Injectors??

Paul Workman · 03-31-2012

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

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

P.

FU · 03-31-2012

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

GOLDCYLON · 03-31-2012

Got to be the injectors. What brand are they?

HAWAIIZR-1 · 03-31-2012

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

XfireZ51 · 03-31-2012

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.

03-31-2012	#1
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,702	Doing Plug Cuts 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: 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. Injectors?? __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

03-31-2012	#3
FU Join Date: Mar 2004 Location: Found Member Posts: 4,346	Re: Doing Plug Cuts Sure look's like injectors. Get them flow tested while it's still apart. __________________ Frank Urbo. NCM Lifetime member # 982 Registry Founding # 237

03-31-2012	#4
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,155	Re: Doing Plug Cuts Got to be the injectors. What brand are they? __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

03-31-2012	#5
HAWAIIZR-1 Join Date: May 2010 Location: Japan Posts: 3,581	Re: Doing Plug Cuts Great stuff Dom. Thanks for sharing and very interesting information. __________________ Craig "ZR-1 NO KA 'OI" "ZR-1 ICHIBAN" 1995 #228 Black/Black with Dunn Heads ZR-1 owner since September 2003 ZR-1 Net Registry Founding Member #0074 NCM Lifetime Member #2048

03-31-2012	#6
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,702	Re: Doing Plug Cuts 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. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

03-31-2012	#2
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: Doing Plug Cuts It appears #2 & 4 are running rich? And, #7 looks to be lean, no? Hmmmmm.... when were the injectors last replaced??? P. __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry