Where is it coming from

Rbcconst · Aug 17, 2017

Just had my heads done, carb re built. What is this and how did it get there? Boat ran good for an hour, did have a little backfire twice at the end of the hour the low end idle dropped and would barley run, the top end missed bad and couldn't get more the 4200 rpm, when I picked it up and first ran it the low idle was around 800 and top 4900. 502 motor.

fishing fool · Aug 17, 2017

Valve cover

cnj · Aug 17, 2017

Rbcconst said:
Just had my heads done, carb re built. What is this and how did it get there? Boat ran good for an hour, did have a little backfire twice at the end of the hour the low end idle dropped and would barley run, the top end missed bad and couldn't get more the 4200 rpm, when I picked it up and first ran it the low idle was around 800 and top 4900. 502 motor. View attachment 581022 View attachment 581023 View attachment 581024 View attachment 581025

Valve cover. And that oil looks very dirty. Is it some specialty brand with a dark color?

Trash · Aug 17, 2017

Rbcconst · Aug 17, 2017

cnj said:
Valve cover. And that oil looks very dirty. Is it some specialty brand with a dark color?

Oil is brand new. Doesn't look like that on the dip stick.

LargeOrangeFont · Aug 17, 2017

Leaky valve cover gasket maybe, or breathers.

rivrrts429 · Aug 17, 2017

What breathers are you running?

Rbcconst · Aug 17, 2017

rivrrts429 said:
What breathers are you running?

Idk what kind but they run from the valve covers to the air cleaner! Could it be coming up the tubes?

LargeOrangeFont · Aug 17, 2017

Could be. Is there oil residue all over or a trail of oil?

Rbcconst · Aug 17, 2017

LargeOrangeFont said:
Could be. Is there oil residue all over or a trail of oil?

I pulled the air cleaner and the bottom of it is soaked in oil. Definitely looks like it came from the breathers. There is a lot of oil everywhere.

79 HUSTLER · Aug 17, 2017

You've got some serious blow-by going on. Could be anything from rings to valves.

Cray Paper · Aug 17, 2017

That oil is black, if the oil is fresh it has to be from blow by. hard to tell from the pics, but the down lip of the valve covers looks like they are hitting the tops of the intake manifold runners. For some reason the black oil looks like it's really thin...like it has gas mixed in it also. Also noticed what looks like an EGR port filled with black oil on the drivers side of the engine. What is the port cast in to the intake manifold just below the carb mounting point for?

Rbcconst · Aug 17, 2017

IROCDave said:
That oil is black, if the oil is fresh it has to be from blow by. hard to tell from the pics, but the down lip of the valve covers looks like they are hitting the tops of the intake manifold runners. For some reason the black oil looks like it's really thin...like it has gas mixed in it also. Also noticed what looks like an EGR port filled with black oil on the drivers side of the engine. What is the port cast in to the intake manifold just below the carb mounting point for?

The oil is fresh. They did compression test on the motor and all seemed to be ok between 125-140. The heads were just re done. I'm not sure what that port is for. I pulled the air cleaner off and it was soaked in oil on the bottom.

Rbcconst · Aug 17, 2017

79 HUSTLER said:
You've got some serious blow-by going on. Could be anything from rings to valves.

Heads were just re done. They did a compression test on it and all were between 125-140. Anything else it could be?

mjc · Aug 17, 2017

IROCDave said:
That oil is black, if the oil is fresh it has to be from blow by. hard to tell from the pics, but the down lip of the valve covers looks like they are hitting the tops of the intake manifold runners. For some reason the black oil looks like it's really thin...like it has gas mixed in it also. Also noticed what looks like an EGR port filled with black oil on the drivers side of the engine. What is the port cast in to the intake manifold just below the carb mounting point for?

The cast port is for the choke coil that GM uses.

Deadendgraphics · Aug 18, 2017

I'd get rid of that breather system. It will always be a mess at high revs.
Check the intake bolts and valve covers. Valve covers usually leak on the header side.
What's your oil pressure?
I say intake because it sounds like you got a leak...

rrrr · Aug 18, 2017

I think perhaps your engine guy used the wrong head gaskets or flipped them upside down and they are blocking oil drain back passages. This looks like a good guess, there's a hella lot of oil on the top end of that engine. If the passages are blocked, the oil pressurizes the valve cover cavity, then the oil is forced out around the valve cover gaskets and through the breather tubes.

It's possible your valve covers may have been overtightened, which pushed the gaskets out of place. But that wouldn't explain the oil in the flame arrestor (it's not an air cleaner).

There's nothing wrong with your breather setup, there are a jillion boats with the valve covers plumbed into the flame arrestor and they don't pass oil. Something else is going on.

You can remove the valve covers and check the drain back passages with a long 1/8" screwdriver or awl. The passages are both ends of each head, in a depression and a bit larger than 1/4" diameter. If the top of the head has puddled oil up to the valve cover bottom lip from front to back it's a sign there's blockage. At the same time you can check the valve cover gaskets. Torque the valve cover bolts to 12 ft lbs, that's plenty tight.

If your intake manifold was leaking enough to pass that much oil the engine wouldn't have done 4900 RPM and there wouldn't be oil in the flame arrestor. Besides, there aren't any oil passages in the manifold, so there's no oil to leak. That's not the problem.

It's running crappy because your timing may have been off a bit, causing the backfire, which blew the power valve in your carburetor. There may a couple other problems with the carb.

4Waters · Aug 18, 2017

rrrr said:
I think perhaps your engine guy used the wrong head gaskets or flipped them upside down and they are blocking oil drain back passages. This looks like a good guess, there's a hella lot of oil on the top end of that engine. If the passages are blocked, the oil pressurizes the valve cover cavity, then the oil is forced out around the valve cover gaskets and through the breather tubes.

It's possible your valve covers may have been overtightened, which pushed the gaskets out of place. But that wouldn't explain the oil in the flame arrestor (it's not an air cleaner).

There's nothing wrong with your breather setup, there are a jillion boats with the valve covers plumbed into the flame arrestor and they don't pass oil. Something else is going on.

You can remove the valve covers and check the drain back passages with a long 1/8" screwdriver or awl. The passages are both ends of each head, in a depression and a bit larger than 1/4" diameter. If the top of the head has puddled oil up to the valve cover bottom lip from front to back it's a sign there's blockage. At the same time you can check the valve cover gaskets. Torque the valve cover bolts to 12 ft lbs, that's plenty tight.

If your intake manifold was leaking enough to pass that much oil the engine wouldn't have done 4900 RPM and there wouldn't be oil in the flame arrestor. Besides, there aren't any oil passages in the manifold, so there's no oil to leak. That's not the problem.

It's running crappy because your timing may have been off a bit, causing the backfire, which blew the power valve in your carburetor. There may a couple other problems with the carb.

^^^^^^ This, the only thing he left out is if your drain back holes are plugged then you could have run the bottom end without oil or scavenging for oil, so it might be a good idea to pull the engine and check the main and rod bearings.

fishing fool · Aug 18, 2017

Have you tried a different prop?

Where is it coming from

Rbcconst

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fishing fool

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cnj

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Trash

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Rbcconst

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LargeOrangeFont

We aren't happy until you aren't happy

rivrrts429

Arch Stanton...

Rbcconst

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LargeOrangeFont

We aren't happy until you aren't happy

Rbcconst

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79 HUSTLER

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Cray Paper

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Rbcconst

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Rbcconst

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mjc

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Deadendgraphics

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rrrr

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fishing fool

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