White deposits in exhaust ports - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Michael A. K. G · 09-09-2002, 10:20 PM

Hi folks.

I just removed the exhaust manifold on my 250 inline 6, and the inside of all the exhaust ports and the exhaust manifold are coated with white powdery residue. It's rather thick -- about 1/16 inch (not just a light coating), and it comes right off in chunks when "persuaded" with a finger. I've seen manifolds full of black powdery gunk, from running too rich, but not t his white stuff. Is this perhaps burned soot?

The truck had been running rich (probably for quite a while) when I got it; the idiot previous owner had disconnected the metering rod (and done lots of other really stupid things). So its history does resemble what I described above.

Any ideas what this might be? Am I talking out of my posterior?

The intake ports are yellow on the inside. Not nearly as thick as the exhaust deposits. Is this just 30 years of gasoline?

TIA

cableguy0 · 09-09-2002, 10:36 PM

im pretty sure white is from a lean conditon

Johns70 · 09-09-2002, 10:37 PM

i'm not forsure, might be wrong but i think white is too lean.

jostrans68 · 09-10-2002, 01:32 AM

My .02 in most cases it is the remains of the additives in todays gas. I have seen them almost pure white to a light pink.

O'l Buck · 09-11-2002, 01:32 AM

if I remember right, white is lean, and it will also be built up heavy on your exhaust valves, pouring transmission fluid slowly in your carb at high idle will actually break up the white carbon and get rid of it for ya.

*Fast68Chevy* · 09-11-2002, 01:46 PM

white is always found on exhaust valves and sometiems in ports, its burnt additives of some kind or form, whtehr it be already in the fuel or added into the tank, its ok and wont hurt anything

good luck

09-09-2002, 10:20 PM	#1
Michael A. K. G Registered User Join Date: Jul 2002 Location: California central coast Posts: 126	White deposits in exhaust ports Hi folks. I just removed the exhaust manifold on my 250 inline 6, and the inside of all the exhaust ports and the exhaust manifold are coated with white powdery residue. It's rather thick -- about 1/16 inch (not just a light coating), and it comes right off in chunks when "persuaded" with a finger. I've seen manifolds full of black powdery gunk, from running too rich, but not t his white stuff. Is this perhaps burned soot? The truck had been running rich (probably for quite a while) when I got it; the idiot previous owner had disconnected the metering rod (and done lots of other really stupid things). So its history does resemble what I described above. Any ideas what this might be? Am I talking out of my posterior? The intake ports are yellow on the inside. Not nearly as thick as the exhaust deposits. Is this just 30 years of gasoline? TIA

09-09-2002, 10:36 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	im pretty sure white is from a lean conditon __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

09-09-2002, 10:37 PM	#3
Johns70 Registered User Join Date: Dec 2001 Location: Spring Creek, nevada. U.S.A. Posts: 456	i'm not forsure, might be wrong but i think white is too lean. __________________ 69 chevy short wide box project 70 GMC jimmy project

09-10-2002, 01:32 AM	#4
jostrans68 Jostrans68 Join Date: Mar 2001 Location: Bloomington indiana Posts: 1,182	My .02 in most cases it is the remains of the additives in todays gas. I have seen them almost pure white to a light pink. __________________ [CGTW Member former 67-72 now with a 96 silverado

09-11-2002, 01:32 AM	#5
O'l Buck Recovering Truck Driver Join Date: Mar 2002 Location: Orleans, NE USA Posts: 1,883	if I remember right, white is lean, and it will also be built up heavy on your exhaust valves, pouring transmission fluid slowly in your carb at high idle will actually break up the white carbon and get rid of it for ya. __________________ 67 K-20 350, SM465, Eaton rear, 4.56 no spin option 00 Dodge 2500 4x4, 24V cummins, 5 speed Chad South Central Nebraska

09-11-2002, 01:46 PM	#6
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	white is always found on exhaust valves and sometiems in ports, its burnt additives of some kind or form, whtehr it be already in the fuel or added into the tank, its ok and wont hurt anything good luck



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