Exhaust manifold gasket keeps burning up - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jltonline · 05-07-2012, 11:27 PM

71 C20 with a 350 that looks stock. The driver's side exhaust manifold was leaking so I replaced the gasket. Less than 100 miles later it started leaking again. I pulled it off and it burnt through the cork on the 2 center ports. Do I need to have the manifold machined/replaced?

TobyArnot · 05-08-2012, 07:17 AM

FIRST! Welcome to the Board,

-
Now, most stock manifolds don't really need the gaskets, unless it's severally warped, which I doubt. Clean the manifold and port surfaces with a Scotchbrite pad and bolt it on without a gasket. Bet it won't leak, at least worth a try.

mrein3 · 05-08-2012, 07:37 AM

Quote:

Originally Posted by TobyArnot

FIRST! Welcome to the Board,

-
Now, most stock manifolds don't really need the gaskets, unless it's severally warped, which I doubt. Clean the manifold and port surfaces with a Scotchbrite pad and bolt it on without a gasket. Bet it won't leak, at least worth a try.

I agree.
I have NEVER used a gasket between a factory head and a factory exhaust manifold.

jltonline · 05-08-2012, 12:37 PM

Thanks for the welcome. Here are a couple pics. This is on the center ports. I torqued the outer bolts to 17ft-lbs and the center bolts to 27ft-lbs per Chilton's manual. I will clean it and bolt it together without the gaskets to see if it makes a difference.

This is the metallic side that still looks good.

This is the cork material that has already burned away.

68gmsee · 05-08-2012, 01:33 PM

Check to make sure that the manifold is completely flat as mentioned above. If you're not sure have them machined. I've gone the gasket and no gasket route and haven't had any problems either way, however, just a slight deviation from completely flat will eventually burn the gasket if you use one.

If you use a gasket, install the gasket with the steel face toward the manifold and the fiber surface against the head. (Federal Mogul site)

**425HP409** · 05-08-2012, 02:39 PM

I have never used gaskets as that is the way Chevrolet built the trucks. The gaskets are to make up for any small deviation in the flatness of the manifold. make sure that when you have the manifold off of the truck that you take a flat file and file the surface of the manifold and the head and you will not have any other problems.

buz48 · 05-08-2012, 06:58 PM

I have built 2 motors 1 I used Patroit headers with the gaskets you showed in your pics. And they never leaked The other I used Headman headers and the best gaskets you can get and them suckers leak no matted what I do!!!!
Buz 48

midniteblues · 05-08-2012, 07:19 PM

headers or manifolds they are the gaskets too use Ive had very few issues with them.
there has to be a irregular suface either on the head or the manifold

JimKshortstep4x4 · 05-08-2012, 08:06 PM

Have you been putting the gaskets on with the metal facing the manifold? The manifolds get hotter then the heads so it is better to have the metal toward them.

Jim

jltonline · 05-08-2012, 09:35 PM

Quote:

Originally Posted by JimKshortstep4x4

Have you been putting the gaskets on with the metal facing the manifold? The manifolds get hotter then the heads so it is better to have the metal toward them.

Jim

I put them on with the metal facing the heads. I assumed they would get hotter. I am going to pull the manifold off and take it to a friend who has a machine shop.

68gmsee · 05-08-2012, 10:01 PM

Quote:

Originally Posted by jltonline

I put them on with the metal facing the heads. I assumed they would get hotter. I am going to pull the manifold off and take it to a friend who has a machine shop.

Reread my post above. Steel face should be towards exhaust and perforated material should be to the head. Federal Mogul explains the reason why.

btw: the material is a heat resistant material and not cork which wouldn't last very long at all.

old Chevy guy · 05-09-2012, 01:27 AM

I always use a large flat file and hold it from the two ends and go side ways over the surface of the stock manifold till is all flat and shiny every where it will contact the head. An older ''Chevy guy'' showed me that around 25 or 30 years ago. No gaskets no problem ever. Seems to work much much better than if you tryed to use the file the long way. It needs to be a good sharp file.

midniteblues · 05-09-2012, 08:12 AM

the sealing surface looks pretty rough If you have a way to keep it extremly flat you could very lightly hit it with a belt/disc sander then finish it with a file but it must be flat and level.

MARKDTN · 05-09-2012, 08:44 AM

Quote:

Originally Posted by midniteblues

the sealing surface looks pretty rough If you have a way to keep it extremly flat you could very lightly hit it with a belt/disc sander then finish it with a file but it must be flat and level.

It almost looks like the port on the left in the photo is not flat at all. May just be the photo. I would clean it up and use a long straightedge to check it.

68gmsee · 05-09-2012, 09:41 AM

Yeah, I agree with above. Looks rough. Machine shop shouldn't charget that much to level it off for you if they have the proper equipment.

05-07-2012, 11:27 PM	#1
jltonline Registered User Join Date: Apr 2012 Location: Ferndale, CA Posts: 6	Exhaust manifold gasket keeps burning up 71 C20 with a 350 that looks stock. The driver's side exhaust manifold was leaking so I replaced the gasket. Less than 100 miles later it started leaking again. I pulled it off and it burnt through the cork on the 2 center ports. Do I need to have the manifold machined/replaced? Last edited by jltonline; 05-07-2012 at 11:34 PM. Reason: Clarification

05-08-2012, 07:17 AM	#2
TobyArnot Quit if it's not FUN!!! Join Date: Jul 2010 Location: Indian Trail, N.C, Posts: 864	Re: Exhaust manifold gasket keeps burning up FIRST! Welcome to the Board, - Now, most stock manifolds don't really need the gaskets, unless it's severally warped, which I doubt. Clean the manifold and port surfaces with a Scotchbrite pad and bolt it on without a gasket. Bet it won't leak, at least worth a try. __________________ MY MOTTO: Eat it all up, Wear it out, Use the last few drops, Spend all you've got, Late in life, you'll think of the things you didn't do, not the things you did. - Get out and experience life ! . Robbie Robinson a.k.a. TobyArnot (Toe Bee or not toe bee)

05-08-2012, 12:37 PM	#4
jltonline Registered User Join Date: Apr 2012 Location: Ferndale, CA Posts: 6	Re: Exhaust manifold gasket keeps burning up Thanks for the welcome. Here are a couple pics. This is on the center ports. I torqued the outer bolts to 17ft-lbs and the center bolts to 27ft-lbs per Chilton's manual. I will clean it and bolt it together without the gaskets to see if it makes a difference. This is the metallic side that still looks good. This is the cork material that has already burned away. __________________ 71 C-20

05-08-2012, 01:33 PM	#5
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Exhaust manifold gasket keeps burning up Check to make sure that the manifold is completely flat as mentioned above. If you're not sure have them machined. I've gone the gasket and no gasket route and haven't had any problems either way, however, just a slight deviation from completely flat will eventually burn the gasket if you use one. If you use a gasket, install the gasket with the steel face toward the manifold and the fiber surface against the head. (Federal Mogul site)

05-08-2012, 02:39 PM	#6
425HP409 425hp409 Join Date: Oct 2008 Location: Prosper Texas Posts: 841	Re: Exhaust manifold gasket keeps burning up I have never used gaskets as that is the way Chevrolet built the trucks. The gaskets are to make up for any small deviation in the flatness of the manifold. make sure that when you have the manifold off of the truck that you take a flat file and file the surface of the manifold and the head and you will not have any other problems. __________________ Charles 68 SWB, Dad bought new, now 396 & factory ac 64 Impala SS, 409 425HP, 4 speed AC 64 Bel Air Wagon, 400 Small Block 57 Bel Air all original 283 w/Factory Air 77 GMC Sprint, 454/425HP 67 Olds 442, all original 90 ZR1 Corvette

05-08-2012, 06:58 PM	#7
buz48 Registered User Join Date: Jan 2011 Location: Paragould Ar. Posts: 41	Re: Exhaust manifold gasket keeps burning up I have built 2 motors 1 I used Patroit headers with the gaskets you showed in your pics. And they never leaked The other I used Headman headers and the best gaskets you can get and them suckers leak no matted what I do!!!! Buz 48

05-08-2012, 07:19 PM	#8
midniteblues Registered User Join Date: Jul 2011 Location: strausstown pa Posts: 3,394	Re: Exhaust manifold gasket keeps burning up headers or manifolds they are the gaskets too use Ive had very few issues with them. there has to be a irregular suface either on the head or the manifold __________________ 81 camaro 355 4/spd 342 posi my first love. 67 swb step 454/4spd ott 373 posi 4/7 drop. 2000 s10 zr2 little blue truck that never gets stuck. '74 heald super bronc vt8. tecumseh powered moon rover.

05-08-2012, 08:06 PM	#9
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Exhaust manifold gasket keeps burning up Have you been putting the gaskets on with the metal facing the manifold? The manifolds get hotter then the heads so it is better to have the metal toward them. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

05-09-2012, 01:27 AM	#12
old Chevy guy Registered User Join Date: Apr 2007 Location: Foster Rhode Island Posts: 1,176	Re: Exhaust manifold gasket keeps burning up I always use a large flat file and hold it from the two ends and go side ways over the surface of the stock manifold till is all flat and shiny every where it will contact the head. An older ''Chevy guy'' showed me that around 25 or 30 years ago. No gaskets no problem ever. Seems to work much much better than if you tryed to use the file the long way. It needs to be a good sharp file.

05-09-2012, 08:12 AM	#13
midniteblues Registered User Join Date: Jul 2011 Location: strausstown pa Posts: 3,394	Re: Exhaust manifold gasket keeps burning up the sealing surface looks pretty rough If you have a way to keep it extremly flat you could very lightly hit it with a belt/disc sander then finish it with a file but it must be flat and level. __________________ 81 camaro 355 4/spd 342 posi my first love. 67 swb step 454/4spd ott 373 posi 4/7 drop. 2000 s10 zr2 little blue truck that never gets stuck. '74 heald super bronc vt8. tecumseh powered moon rover.

05-09-2012, 09:41 AM	#15
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Exhaust manifold gasket keeps burning up Yeah, I agree with above. Looks rough. Machine shop shouldn't charget that much to level it off for you if they have the proper equipment.



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