OIL LEAK from top rear of motor...HELP!!

[CEE1NG_RED]

The PO installed a '78 350 small block motor in the '67. I had the gasket changed from the valve covers and intake manifold, but it still leaks oil at the top rear of the intake manifold despite the new gaskets installed. My buddy, a mechanic, says that the PO put silicone in that area. He noticed that the block had a slight slope or groove like a hole where it connects to the intake manifold, but it is not a crack nor a hole on motor/block and suggested that the intake manifold may not be an exact match for the block (eventhough it sits flushed, but there is a small groove/slope like a screw on the back of the top block where the manifold bolts to) that's why the PO put silicone on it as a temp fix before I purchased it. So for the time being, he put silicone on it as well til we get this figured out.

Anyways, he did not take a pic of what he was trying to explain to me, but maybe you guys/gals can shed some light. The area is near the oil pressure sender (but no oil is is evident on the sending unit).

Is there anyway I can identify the intake manifold (by part# or brand) so I can determine if it is made for my '78 chevy 350 motor. HELP please!!

[bk2life]

your 1978 motor is about th emost common motor ever built in the history of motors.

if its the worng intake, CL a new one for probably around 50 bucks..

but without pictures its purely a guessing game.

myabe distributor gasket is gone and its leaking there?

if it definitealy is the intake, pull it off and redo it.

[88Jimmy4x4]

is the intake stock or aftermarket aluminum?

[S10Fan]

Is the oil sending unit back there? They leak as a sport at times. As mentioned, the distributor gasket is also a possibility. I like to use Permatex Ultra-Gray sealer on my intake manifolds (front and rear) and have experienced zero leaks. Run a bead about 3/8" and let it set a couple minutes, place the intake and bolt it down.

Here's the sealer, I've found the best price at Walmart. http://automotive.hardwarestore.com/...er-662054.aspx

[Wrecked1982]

+1 the small oil pipe with the oil sensor at the back might have bent/crack when installing engine

[GM-power]

Did you use a rubber gasket or use rtv?
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[CEE1NG_RED]

How can I tell if it's an aftermarket or stock intake manifold?? My friend used rubber gasket. It is not the oil pressure screw/valve leak nor the intake covers. He said that the motor had a slight pinky size dip where the intake manifold connects flat with, but the intake manifold did not connect completely flat to in that small area so he put silicone as a temp fix.

Anyone with a '78 350 motor verify this dip on the rear top motor where the intake manifold is suppose to be flushed with???


Lastly, Is there a good HOW TO vid. or so to take/remove intake manifold and change the gasket??

[SSC's76]

there should be no small dip in the casting. the only thing back there is the hole for the oil sender. if rubber gaskets were used especially without some sort of sealer that's where its coming from. its not to hard to detect a leak back there if you can get the front of the truck up a little bit you have a straight visual shot into that area from below. removing the intake isn't hard drain as much coolant as you can remove 1 valve cover either side pull the distributor out disconnect the fuel line and linage and unbolt it. you can leave the carb on or take it off before you pull the intake off.


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[silvereagle07]

Throw the rubber gaskets away and use a bead of silicone.
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[88Jimmy4x4]

Originally Posted by CEE1NG_RED

How can I tell if it's an aftermarket or stock intake manifold?? My friend used rubber gasket. It is not the oil pressure screw/valve leak nor the intake covers. He said that the motor had a slight pinky size dip where the intake manifold connects flat with, but the intake manifold did not connect completely flat to in that small area so he put silicone as a temp fix.

Anyone with a '78 350 motor verify this dip on the rear top motor where the intake manifold is suppose to be flushed with???


Lastly, Is there a good HOW TO vid. or so to take/remove intake manifold and change the gasket??

never use those rubber gaskets, always use RTV....you really need to take some pics and post them

[CEE1NG_RED]

...STILL LEAKING!! Had a mechanic do the work and he said there's a valley groove on the top where the intake connects with the top, and that the gasket did not compensate with that valley groove. So, RTV was used, but it started to leak a week later. I have a '78 motor and had ordered the exact gasket part for it, but no avail. Is it possible that the top has a crack or missing a piece? My friend didn't get a chance to take a pic. Does anyone have a picture of this valley groove in the rear top portion of the motor where the intake connects. It's not the oil pressure sending unit. It's right next to it. Anyways, if you have a '78 350 and have a pic or idea what I am talking about, please LMK.

[anubisani]

take the intake off , go and get some RIGHT STUFF from local auto parts , lay a thick bead front and back of block wait till it gets tacky where it is not wet usually 5 mins then lay the intake down . your problem will be solved

[Rufton]

Method I have high confidence in:

Hospital clean china wall; paying much attention where china wall meets head gasket.
Spray a gasket china wall/HG interface first using tool to work in.
Spray a gasket both flanges.
Ultra RTV dab china wall/HG interface and squeeze in w/ finger.
Discard china wall rubber/cork gasket.
Ultra RTV water ports and china wall.
Assemble immediately.
Use studs to assure intake drops true.
Verify china wall RTV squeeze out looks correct.

[CEE1NG_RED]

Another thing is why engine oil leaking from the top after not running the truck for a week??? Do you guys think that the top block has a chip in it from the rear, where it connects with the intake? Haven't driven the truck since Jan 2013!!!