1968 GTO 400 engine oil leak??? - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 05-19-2018, 01:58 AM Thread Starter
 
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1968 GTO 400 engine oil leak???

Hello All: This is Bob again. Nick name: The "Z" Man..
My new 68 GTO got a very slow oil leak. My mechanic says it's coming from the Manifold leaking out the back, and running down pass the Distrubutor shaft under the engine. We ruled out the rear main seal??? What is needed to fix the problem. Is it a big job? I think the Manifold gasket could be made out of cork or rubber? Is it a good Idea to add a bottle of "OIL STOP LEAK" to the oil, and wait and see if this fixes the oil leak???? I'm using which I got off this wed site.
Brad Penn 10w30w. A K&N oil filter. Any information will be great. Also I live in Clearwater florida. Anyone else around here a GTO fan????

Thank you, The "Z" Man :-)
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post #2 of 4 (permalink) Old 05-19-2018, 03:46 AM
 
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"...My mechanic says it's coming from the Manifold leaking out the back, and running down pass the Distrubutor shaft under the engine..."


If your engine is a Pontiac 400, that can't happen. The dist does not go thru the intake manifold, like on a small block Chevy.

I suppose it is possible that oil could leak out from under the back of the valley cover and run by the dist housing.

I once had a used Mallory dual point dist which developed an oil leak up the shaft & into the cap area. Would obviously cause misfire problems, especially at higher rpm. Took it out and went to a factory single point dist, and never had any more ignition problems. Lots of guys nowadays think they need elec ignition with an MSD box. Fact is, lots of engines ran just fine, including Pontiac race engines, long before the elec ignition systems became standard equipment. Yes, I know that this last paragraph has absolutely nothing to do with the question. Please forgive my ramblings.
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post #3 of 4 (permalink) Old 05-19-2018, 09:14 AM
 
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It could be leaking past the intake gasket section which covers the open casting holes in the head found on each side of the exhaust crossover, between each intake runner pair. When you pull the intake & gasket, you will see the pushrods. However, I have never experienced a leak here, but it could be possible. I would make sure that the mating surfaces on the intake are "true" and not warped or damaged in some way. Clean all mating surfaces thoroughly.

When re-installing the intake/gasket, make sure you torque the intake bolts evenly - BUT, there is a long bolt at the front of the intake-to-water pump that applies pressure to the rubber O-ring that seals the water pump to the intake. Clean both surfaces, install the new rubber O-ring seal, and torque this bolt first to draw the intake forward and up against the rubber O-ring to seal it. If not done this way, you may have a water leak. Once done, then install & torque down the manifold bolts.

Another place to check is your valve cover gasket. These can leak and drip down past the intake manifold and go out the back at the distributor. Often, if the original steel valve covers are used, people will over tighten the small bolts and crush the gasket and dimple the valve cover holes downward. So when you go to install a new set of gaskets, they don't clamp as well as they should and can let oil leak out. Always straighten these holes where the small bolts go through - make them flat and even again. Valve cover "hold down tabs" can spread the clamping force over a greater area to help prevent the valve cover hole crush. I have used the small type, but they come in a variety of styles if you want to dress up the engine: https://www.summitracing.com/search/...hold-down-tabs

As bigD stated, oil could be coming out of the valley pan under the intake manifold, but would be hard to tell without removing the intake. Also check the rubber grommet found in the valley pan which your PCV valve fits into. Over time these dry out/rot and oil could be coming from a bad grommet. You should be able to see this if this is the problem.

....and oil could be coming out from under the distributor housing base where it goes into the block, but if your mechanic said it is going past the distributor housing, then it would be some place forward of it.

DO NOT USE any form of stop leak or other additive - just not a good idea if you plan on keeping the car. Fixing it right is really not a big job.
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post #4 of 4 (permalink) Old 05-19-2018, 09:53 PM Thread Starter
 
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1968 GTO manifold oil leak

Hello BigD, and Jim: Would like to Thank you for you good advice again.
I will get back to my Mechanic, and go from there. He wants to pull off the Manifold and carburator. I just like to make sure where in the right area. Don't want to do something, and not fix the problem. I'll check the right valve cover.
It is all wet back there. I keep cleaning the back of the engine. After a day there's oil back there again. It's such a hard place to get to. :-(
Well, I'll let you know what we do.... The drama continues... LOL LOL

The "Z" Man :-)
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