Intake manifold gasket question
Thread Starter
Pro
Joined: May 2013
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Intake manifold gasket question
I believe I have a leak at the back side of my intake manifold under the distributor. Is it possible to repair this leak with the gasket material you can get in a tube? What is the best brand to use?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
FelPro makes a round gasket that fits between the dizzy and intake that should take care of that problem. Obviously you have to remove the dizzy to install the gasket. But that will give you the opportunity to clean the area thoroughly.
You really shouldn't apply any goop (RTV) in that area due to the fact that someday you may have to change the IGN timing.
If you are referring to the china wall leaking, that's a whole different ballgame requiring removal of the intake. Never had luck applying a bunch of RTV to stop the leak.
You really shouldn't apply any goop (RTV) in that area due to the fact that someday you may have to change the IGN timing.
If you are referring to the china wall leaking, that's a whole different ballgame requiring removal of the intake. Never had luck applying a bunch of RTV to stop the leak.
Last edited by HeadsU.P.; Mar 5, 2019 at 09:26 AM.
Race Director
Joined: May 2006
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If you referring to the area between the intake and block, degrease it and try applying RTV using one of the brand names. Let it fully cure 24 hours before starting the engine. .
Last edited by MelWff; Mar 5, 2019 at 10:23 AM.
Thread Starter
Pro
Joined: May 2013
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yes. Between the intake manifold and block. I think I am getting a vacuum leak there. I would rather not remove the intake if I can apply a repair externally.
Le Mans Master
Joined: Jan 2001
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The correct thing to to would be to remove the intake and install cleanly.....but you can try just cleaning and resealing. I would NOT use RTV, I would go get some of that "THE RIGHT STUFF" instead. It works great and it works fast.
Clean the area, degrease as best you can, then try to goop on some of that "THE RIGHT STUFF". It will dry fast and you'll know if it's going to work or not. It's more expensive than RTV but well worth it. You'll know quickly.
I would just pull the intake manifold since it's all so easy - but I understand what you're trying to do.
Clean the area, degrease as best you can, then try to goop on some of that "THE RIGHT STUFF". It will dry fast and you'll know if it's going to work or not. It's more expensive than RTV but well worth it. You'll know quickly.
I would just pull the intake manifold since it's all so easy - but I understand what you're trying to do.
Race Director
Joined: May 2006
Posts: 18,737
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If the you have the intake vacuum leak in the back of the engine under the distributor you can apply sealant there all day long and still have a intake manifold gasket leak in the engine valley, the intake has to come off.
Thread Starter
Pro
Joined: May 2013
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if I seal up that opening where else can air get in?
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Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
We need to take three steps back before going forward and get everybody on the same page.
First you said you have a leak at the rear of the intake manifold. Most people would think, oil leak.
Now you say a vacuum leak. There is no vacuum or pressure at the location you described.
And there shouldn't be any gasket there either. Only Black RTV, The Right Stuff.
So lets get all this straight. What makes you suspect a vacuum leak? You used a vacuum gauge? Had a low reading? Car runs like crap?
The intake gaskets AT the cylinder head could leak and give you a vacuum leak. But those issues are hard if not impossible to detect.
So fill us in on your evaluation.
First you said you have a leak at the rear of the intake manifold. Most people would think, oil leak.
Now you say a vacuum leak. There is no vacuum or pressure at the location you described.
And there shouldn't be any gasket there either. Only Black RTV, The Right Stuff.
So lets get all this straight. What makes you suspect a vacuum leak? You used a vacuum gauge? Had a low reading? Car runs like crap?
The intake gaskets AT the cylinder head could leak and give you a vacuum leak. But those issues are hard if not impossible to detect.
So fill us in on your evaluation.
Thread Starter
Pro
Joined: May 2013
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I admit I a still learning how everything functions mechanically. I believe I have I have a vacuum leak and assumed the intake manifold could be a source. There is a small amount of oil seepage at the rear where it meets the block.
I have not gone through the process of trouble shooting to locate the source of the vacuum leak but do have a plan based on advice from Lars who is well know on this forum.
The reason I believe there is a vacuum leak is due to the idle speeding up after driving the car for a while and also have a dieseling problem where the engine continues to run after shutoff.
I have not gone through the process of trouble shooting to locate the source of the vacuum leak but do have a plan based on advice from Lars who is well know on this forum.
The reason I believe there is a vacuum leak is due to the idle speeding up after driving the car for a while and also have a dieseling problem where the engine continues to run after shutoff.
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
You may indeed have a vacuum leak at the intake but that will only occur at the intake runners. The lifter valley has no bearing on engine vacuum but does have oil in it.
If you have checked all the vacuum lines by pinching each off, making sure your carb base gasket is sealing, etc and you still have a vacuum leak I would pull the intake and replace the gaskets.
Lots of folks on this site can suggest u tubes or walk you through replacing intake gaskets. Just make sure that is where your vacuum leak is coming from first.
If you have checked all the vacuum lines by pinching each off, making sure your carb base gasket is sealing, etc and you still have a vacuum leak I would pull the intake and replace the gaskets.
Lots of folks on this site can suggest u tubes or walk you through replacing intake gaskets. Just make sure that is where your vacuum leak is coming from first.
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
you don't say what year yours is ... should always state year & motor size everytime you seek input.
some motors have either a mechanical oil pressure fitting or an electric oil pressure sender screwed into the china wall adjacent to distributor.
It's common for them to leak ... especially sender.
some motors have either a mechanical oil pressure fitting or an electric oil pressure sender screwed into the china wall adjacent to distributor.
It's common for them to leak ... especially sender.
Thread Starter
Pro
Joined: May 2013
Posts: 570
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you don't say what year yours is ... should always state year & motor size everytime you seek input.
some motors have either a mechanical oil pressure fitting or an electric oil pressure sender screwed into the china wall adjacent to distributor.
It's common for them to leak ... especially sender.
some motors have either a mechanical oil pressure fitting or an electric oil pressure sender screwed into the china wall adjacent to distributor.
It's common for them to leak ... especially sender.
Race Director
Joined: May 2006
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so now we are back to an oil leak and maybe a vacuum leak. The oil leak repair can be attempted as previously stated.
Do you know how to adjust the center carburetors idle speed and mixture when fully warmed up?
What idle speed are you setting the engine to when fully warmed up?
Do you know how to adjust the center carburetors idle speed and mixture when fully warmed up?
What idle speed are you setting the engine to when fully warmed up?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
As far as a possible vacuum leak, these are usually less labor to locate them, than removing the intake and triple carbs, linkage, etc.
So, before you go pulling the intake off, I would concentrate on all the bilzillion miles of rubber vacuum hoses and fittings going all over place for potential leaks.
The best way to isolate the rubber hoses as a possible leak is to remove the main vacuum line off of the back of the carb and plug the carb fitting.
Start it up. Does it run better? Do you have a vacuum gauge and is it reading higher now? If so, its not likely the intake manifold gaskets at fault here. If no change, then it could be the intake gaskets.
So, before you go pulling the intake off, I would concentrate on all the bilzillion miles of rubber vacuum hoses and fittings going all over place for potential leaks.
The best way to isolate the rubber hoses as a possible leak is to remove the main vacuum line off of the back of the carb and plug the carb fitting.
Start it up. Does it run better? Do you have a vacuum gauge and is it reading higher now? If so, its not likely the intake manifold gaskets at fault here. If no change, then it could be the intake gaskets.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Any leak path in the "China wall" between the engine block and the intake manifold would not create a 'vacuum leak' into the intake system. The interior of the engine is usually pressurized and a leak in that area might spew some oil or have some affect on the PCV system. You can try sealing it from the outside; but you may not have much success. No harm, no foul, however. Give it a try.
If you have a vacuum leak into the induction system, check the intake to cylinder head gasket areas, the carb mounting areas, the carb throttle shaft pivot areas, all vacuum related hoses and devices, and the vacuum advance system. Those areas present much more opportunity for a vacuum leak.
If you have a vacuum leak into the induction system, check the intake to cylinder head gasket areas, the carb mounting areas, the carb throttle shaft pivot areas, all vacuum related hoses and devices, and the vacuum advance system. Those areas present much more opportunity for a vacuum leak.
Safety Car
Joined: Nov 2005
Posts: 3,532
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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
The correct thing to to would be to remove the intake and install cleanly.....but you can try just cleaning and resealing. I would NOT use RTV, I would go get some of that "THE RIGHT STUFF" instead. It works great and it works fast.
Clean the area, degrease as best you can, then try to goop on some of that "THE RIGHT STUFF". It will dry fast and you'll know if it's going to work or not. It's more expensive than RTV but well worth it. You'll know quickly.
I would just pull the intake manifold since it's all so easy - but I understand what you're trying to do.
Clean the area, degrease as best you can, then try to goop on some of that "THE RIGHT STUFF". It will dry fast and you'll know if it's going to work or not. It's more expensive than RTV but well worth it. You'll know quickly.
I would just pull the intake manifold since it's all so easy - but I understand what you're trying to do.
It is a very good sealant for the China rails, although I have never used it to try and "reseal" a rail with the manifold still on, I guess it won't hurt to try it. You may luck out, if not, the manifold has to come off. Do not put any on the flange/gasket surfaces if you do take the manifold off. If you do, you probably won't get the manifold off very easy, it's that good. Oh, and don't use the rubber or cork gaskets for the rails that come with the gasket kits, just use the sealant for the entire job.