What Is Causing This? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

wxman1 · 11-02-2003, 01:11 PM

My truck is a 69 C10 P/U with a 350/th350.
About 6 months ago I put on a new intake
manifold (Holley Street Dominator) and a new
carb (Holley 600 cfm 4 bl). Ever since I've
had a problem with oil leaking down the side of the carb. I've put thread sealer on the carb
hold down studs, but that did not stop the
problem. I thought it might be coming out of the
line from the PCV valve, but I've tightened
that hose clamp as much as I dare. The oil
has to be coming from the carb/manifold interface, but I just can't figure out where.

Any ideas?

jim
Mt Juliet
Link to My Pix

my new 72 · 11-02-2003, 01:15 PM

If you have oil coming up through the manifold, you have some serious issues. It is most likely coming from the PCV valve. Just buy a new valve and install it. They are cheap and should be replaced every year or so anyway. I hope it is not coming from inside the intake, if it is it means that you are having bad head troubles.

wxman1 · 11-02-2003, 01:22 PM

Naw, the inside of the intake is as clean
as a baby's behind, no oil stains, nothing.
The PCV valve is only 6 months old. I got
it when I bought the valve covers.

Jim
Mt Juliet

Class of 69 · 11-02-2003, 01:24 PM

There is no oil that travels thru the intake...hence no possible source for the oil. I'm with my new 72...probably coming from the pcv valve. Change it, and hope for the best. Bad rings, and resulting blow by will cause excessive oil to travel thru the pcv valve. I type too slow, just saw your reply. Pull the pcv valve out of the cover while the engine is reved up, and check for blow by.

my new 72 · 11-02-2003, 01:25 PM

Well, the only place it could be getting the oil is from the PCV valve. It doesn't suck vaccum from anywhere else. Evem if it is only six months old I would try a new one. The oil isn't coming from anywhere else I assure you.

oldsub86 · 11-02-2003, 01:35 PM

AT fluid being sucked up through the line to the transmission? How is it shifting? Maybe time for a new vacuum modulator valve?

lukecp · 11-02-2003, 01:42 PM

The AT fluid could be the problem....although it is of course red, while oil is brown/black. Pull off the vaccum modulator line and see if it is wet with tranny fluid on the inside.....

cdowns · 11-02-2003, 01:45 PM

are you sure the oil isn't coming up thru the manifolod bolts it's a very common problem

my new 72 · 11-02-2003, 02:07 PM

He said that the oil is at the base of the carb where it mates to the intake. The intake bolts wouldn't leak oil up there. The trans modulator may be the culprit, but I doubt it.

BLACK AND BLUE 67-72 · 11-02-2003, 03:34 PM

Do you live where there is much dust? And are you sure that it is oil? I have a seepage that looks like oil that runs down the side of the carb, but it is just some gas with dust mixed with it and it looks like oil.

RAT-AT-TACH · 11-02-2003, 04:19 PM

valve cover seals?could they have a leak and spitting oil at high rev.

Orence1 · 11-03-2003, 01:30 AM

I just went through this with my Holley 750. I was positive that I had oil dripping off both the front and back edges of the carb onto my Edelbrock manifold. Felt like oil and looked like oil. Carb is a brand new rebuild by a professional shop. My friend who is a professional mechanic looked and said it was a fuel leak and that gas in small quanities will "varnish" and take on the appearance of oil. I sent the carb back to the shop and he was right. Carb was leaking at the sight glasses in the bowl. He had to double gasket before it was fixed. Check out the fuel leak angle. Good luck.

cableguy0 · 11-03-2003, 01:49 AM

most likely its a fuel leak. fuel will look exactly like oil in small quantities. check the bolts holding on the fuel bowls make sure they are snug do not overtighten them use a 1/4 inch ratchet to check em.also the sight plugs can leak as well as the fuel inlets if they dont have the little metal gasket between them and the carb

gizmo · 11-03-2003, 09:56 AM

Like cdowns said "Check you maniflod bolts" Take them out and put some gasket sealer on them and put them back in. Oil usually leaks out of the center bolts and it does look like it's coming from the Carb.

sactoC10 · 11-03-2003, 11:50 AM

I've been trying to sort out almost the exact same thing on my 71 350/th350. It is not my intake manifold gasket. It is not my intake bolts. It is not even the top of my valve cover gsakets.

I have this "MYSTERY LINE" that I have yet to see on any other 350. It has what looks like a vacuum fitting coming up from where one of the intake bolts should go on the RHS, rubber hose attached that runs down to the front of the engine block to another similar fitting.

Over the weekend I was able to witness this hardened hose (near the carb) leak oil down on to my intake manifold. From there it would pool up, then drip down the back of the engine. It burns once the engine is hot enough...not getting to the ground accept when the engine is running cool.

I cut off the hardened section of rubber hose and reclamped it with a more pliable section. Still do not know what this is. One budy thought the line had to be a water line. It looks like a vacuum line. What I saw puddling there is definitely oil.

These mysteries SUCK, don't they!

11-02-2003, 01:11 PM	#1
wxman1 Senior Member Join Date: May 2002 Location: mt juliet, tennessee, usa Posts: 237	What Is Causing This? My truck is a 69 C10 P/U with a 350/th350. About 6 months ago I put on a new intake manifold (Holley Street Dominator) and a new carb (Holley 600 cfm 4 bl). Ever since I've had a problem with oil leaking down the side of the carb. I've put thread sealer on the carb hold down studs, but that did not stop the problem. I thought it might be coming out of the line from the PCV valve, but I've tightened that hose clamp as much as I dare. The oil has to be coming from the carb/manifold interface, but I just can't figure out where. Any ideas? jim Mt Juliet Link to My Pix

11-02-2003, 01:15 PM	#2
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	If you have oil coming up through the manifold, you have some serious issues. It is most likely coming from the PCV valve. Just buy a new valve and install it. They are cheap and should be replaced every year or so anyway. I hope it is not coming from inside the intake, if it is it means that you are having bad head troubles. __________________ I'm going to Law School, wanna debate? It's good practice.

11-02-2003, 01:24 PM	#4
Class of 69 Registered User Join Date: Mar 2003 Location: Stillwater MN Posts: 1,166	There is no oil that travels thru the intake...hence no possible source for the oil. I'm with my new 72...probably coming from the pcv valve. Change it, and hope for the best. Bad rings, and resulting blow by will cause excessive oil to travel thru the pcv valve. I type too slow, just saw your reply. Pull the pcv valve out of the cover while the engine is reved up, and check for blow by. __________________ 69 GMC K10 ..some restoration required....still..

11-02-2003, 01:25 PM	#5
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	Well, the only place it could be getting the oil is from the PCV valve. It doesn't suck vaccum from anywhere else. Evem if it is only six months old I would try a new one. The oil isn't coming from anywhere else I assure you. __________________ I'm going to Law School, wanna debate? It's good practice.

11-02-2003, 01:35 PM	#6
oldsub86 Registered User Join Date: Dec 2002 Location: Canada Posts: 695	AT fluid being sucked up through the line to the transmission? How is it shifting? Maybe time for a new vacuum modulator valve? __________________ 1968 Chevy - 292 with a powerglide

11-02-2003, 01:22 PM	#3
wxman1 Senior Member Join Date: May 2002 Location: mt juliet, tennessee, usa Posts: 237	Naw, the inside of the intake is as clean as a baby's behind, no oil stains, nothing. The PCV valve is only 6 months old. I got it when I bought the valve covers. Jim Mt Juliet

11-02-2003, 01:42 PM	#7
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	The AT fluid could be the problem....although it is of course red, while oil is brown/black. Pull off the vaccum modulator line and see if it is wet with tranny fluid on the inside..... __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

11-02-2003, 01:45 PM	#8
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	are you sure the oil isn't coming up thru the manifolod bolts it's a very common problem __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

11-02-2003, 02:07 PM	#9
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	He said that the oil is at the base of the carb where it mates to the intake. The intake bolts wouldn't leak oil up there. The trans modulator may be the culprit, but I doubt it. __________________ I'm going to Law School, wanna debate? It's good practice.

11-02-2003, 03:34 PM	#10
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Do you live where there is much dust? And are you sure that it is oil? I have a seepage that looks like oil that runs down the side of the carb, but it is just some gas with dust mixed with it and it looks like oil. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

11-02-2003, 04:19 PM	#11
RAT-AT-TACH Registered User Join Date: May 2003 Location: shawnigan lake b.c. canada Posts: 287	valve cover seals?could they have a leak and spitting oil at high rev.

11-03-2003, 01:30 AM	#12
Orence1 Registered User Join Date: Jan 2000 Location: Bothell, WA Posts: 548	I just went through this with my Holley 750. I was positive that I had oil dripping off both the front and back edges of the carb onto my Edelbrock manifold. Felt like oil and looked like oil. Carb is a brand new rebuild by a professional shop. My friend who is a professional mechanic looked and said it was a fuel leak and that gas in small quanities will "varnish" and take on the appearance of oil. I sent the carb back to the shop and he was right. Carb was leaking at the sight glasses in the bowl. He had to double gasket before it was fixed. Check out the fuel leak angle. Good luck.

11-03-2003, 01:49 AM	#13
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	most likely its a fuel leak. fuel will look exactly like oil in small quantities. check the bolts holding on the fuel bowls make sure they are snug do not overtighten them use a 1/4 inch ratchet to check em.also the sight plugs can leak as well as the fuel inlets if they dont have the little metal gasket between them and the carb __________________ 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.

11-03-2003, 09:56 AM	#14
gizmo 100% Beefcake Join Date: Apr 2001 Location: LaVale, Maryland Posts: 246	Like cdowns said "Check you maniflod bolts" Take them out and put some gasket sealer on them and put them back in. Oil usually leaks out of the center bolts and it does look like it's coming from the Carb. __________________ 1969 C10,350,4:11 posi, Fast Enough 1984 Monte Carlo SS 1987 Chevy S-10, 355 w/150 Shot of Nitrous, Fun,Fun 1938 Nash Lafayette 1956 MG Magnette

11-03-2003, 11:50 AM	#15
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,055	wxman1 (I know your pain!) I've been trying to sort out almost the exact same thing on my 71 350/th350. It is not my intake manifold gasket. It is not my intake bolts. It is not even the top of my valve cover gsakets. I have this "MYSTERY LINE" that I have yet to see on any other 350. It has what looks like a vacuum fitting coming up from where one of the intake bolts should go on the RHS, rubber hose attached that runs down to the front of the engine block to another similar fitting. Over the weekend I was able to witness this hardened hose (near the carb) leak oil down on to my intake manifold. From there it would pool up, then drip down the back of the engine. It burns once the engine is hot enough...not getting to the ground accept when the engine is running cool. I cut off the hardened section of rubber hose and reclamped it with a more pliable section. Still do not know what this is. One budy thought the line had to be a water line. It looks like a vacuum line. What I saw puddling there is definitely oil. These mysteries SUCK, don't they!



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