LT5 Smoking on Startup - ZR-1 Net Registry Forums

Greatlandguy · 08-22-2016

I have a 1991 ZR-1 with the first generation (375 HP) LT5 engine with 36,000 miles on it. I noticed now that upon starting, a significant amount of bluish white smoke emits from both tailpipes for a few seconds and then dissipates. It is not water vapor. No smoke has been observed when driving, though. Associated with this issue is a significant increase in oil usage, I calculated 1/2 quart per 600 miles.

Advice has been given that this could be worn valve guides or valve seals allowing oil into combustion chambers. Any thoughts on cause or diagnostics that can guide me to proper repair would be greatly appreciated!

GOLDCYLON · 08-22-2016

low miles but prob the valve seals and guides as stated since you stated the oil consumption as well. This is something normally confirmed after the tear down. GC

Dynomite · 08-22-2016

I would make sure the PCV system is working. Any oil in the corrugated intake/Air Horn?

Sent from my iPhone using ZR-1 Net Registry

Greatlandguy · 08-22-2016

Thanks for the help, gentlemen. I will check the corrugated air intake and air horn for oil ASAP.

Dynomite · 08-22-2016

Marc Haibeck on oil consumption

Seems you are average on oil consumption if you are driving it fairly hard. If you are just cruising then maybe a bit much on oil consumption. As an example, I just drove 2,000+ miles with 95' and did not use any oil. there was about 4 tablespoons of oil accumulated in my oil catch can

Sent from my iPhone using ZR-1 Net Registry

FU · 08-22-2016

Its normal for an early LT5. They didn't have exhaust oil seals.

cvette98pacecar · 08-22-2016

Dime · 08-23-2016

Quote:

Originally Posted by FU

Its normal for an early LT5. They didn't have exhaust oil seals.

Just the 90s if I'm not mistaken.

GOLDCYLON · 08-23-2016

Quote:

Originally Posted by Dime

Just the 90s if I'm not mistaken.

Correct MY 90 only

32valvesftw · 08-23-2016

The OP did not state how long he has owned the car, so this may be a problem he inherited from the previous owner or a new problem that just surfaced. It would be good to know. I think he should do a compression leak down test. Checking the PCV system is good start IMHO, you might get lucky and avoid the leak down test.

08-22-2016	#1
Greatlandguy Join Date: Jul 2015 Location: Anchorage, Alaska Posts: 8	LT5 Smoking on Startup I have a 1991 ZR-1 with the first generation (375 HP) LT5 engine with 36,000 miles on it. I noticed now that upon starting, a significant amount of bluish white smoke emits from both tailpipes for a few seconds and then dissipates. It is not water vapor. No smoke has been observed when driving, though. Associated with this issue is a significant increase in oil usage, I calculated 1/2 quart per 600 miles. Advice has been given that this could be worn valve guides or valve seals allowing oil into combustion chambers. Any thoughts on cause or diagnostics that can guide me to proper repair would be greatly appreciated!

08-22-2016	#2
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,117	Re: LT5 Smoking on Startup low miles but prob the valve seals and guides as stated since you stated the oil consumption as well. This is something normally confirmed after the tear down. GC __________________ 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

08-22-2016	#3
Dynomite Join Date: Aug 2009 Location: South Dakota/California Posts: 3,815	Re: LT5 Smoking on Startup I would make sure the PCV system is working. Any oil in the corrugated intake/Air Horn? Sent from my iPhone using ZR-1 Net Registry __________________ Clickable links On Iphone Touchable Links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS

08-22-2016	#4
Greatlandguy Join Date: Jul 2015 Location: Anchorage, Alaska Posts: 8	Re: LT5 Smoking on Startup Thanks for the help, gentlemen. I will check the corrugated air intake and air horn for oil ASAP.

08-22-2016	#5
Dynomite Join Date: Aug 2009 Location: South Dakota/California Posts: 3,815	LT5 Smoking on Startup Marc Haibeck on oil consumption Seems you are average on oil consumption if you are driving it fairly hard. If you are just cruising then maybe a bit much on oil consumption. As an example, I just drove 2,000+ miles with 95' and did not use any oil. there was about 4 tablespoons of oil accumulated in my oil catch can Sent from my iPhone using ZR-1 Net Registry __________________ Clickable links On Iphone Touchable Links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 08-27-2016 at 02:48 PM.

08-22-2016	#6
FU Join Date: Mar 2004 Location: Found Member Posts: 4,327	Re: LT5 Smoking on Startup Its normal for an early LT5. They didn't have exhaust oil seals.

08-22-2016	#7
cvette98pacecar Join Date: May 2011 Location: Sydney, Australia Posts: 2,466	Re: LT5 Smoking on Startup

08-23-2016	#10
32valvesftw Join Date: Jun 2015 Location: Texas Posts: 529	Re: LT5 Smoking on Startup The OP did not state how long he has owned the car, so this may be a problem he inherited from the previous owner or a new problem that just surfaced. It would be good to know. I think he should do a compression leak down test. Checking the PCV system is good start IMHO, you might get lucky and avoid the leak down test.