What would cause a milky substance in the throttle body.

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Deadman walking

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Hello it's me again. So after the valve incident about a couple of weeks back I decided to swap the 1980 block,with a 79 400 sbc 4 bolt or at least I think it's a 4 bolt. This block from a 1979 gmc centurion motor home. I swapped the throttle body stuff over to the 400 sbc. Including the TBI heads and intake and cam. I know,I know TBI heads are junk. But.....on the other hand they're great for low end torque and they run damn good on the 400. It will get a little better compression.

I was driving it around for about 2 weeks. Only started when we hit the cold here.I know it isn't leaking any coolant and if it is I'm thinking bad intake seal or something. But some how the throttle body is getting moisture in it. if it's not coolant. maybe the regulator is leaking I'm not sure.

It's not enough apparently to effect the truck the 400 is strong and the cam isnt bald so I reused it.
 

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AuroraGirl

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Hello it's me again. So after the valve incident about a couple of weeks back I decided to swap the 1980 block,with a 79 400 sbc 4 bolt or at least I think it's a 4 bolt. This block from a 1979 gmc centurion motor home. I swapped the throttle body stuff over to the 400 sbc. Including the TBI heads and intake and cam. I know,I know TBI heads are junk. But.....on the other hand they're great for low end torque and they run damn good on the 400. It will get a little better compression.

I was driving it around for about 2 weeks. Only started when we hit the cold here.I know it isn't leaking any coolant and if it is I'm thinking bad intake seal or something. But some how the throttle body is getting moisture in it. if it's not coolant. maybe the regulator is leaking I'm not sure.

It's not enough apparently to effect the truck the 400 is strong and the cam isnt bald so I reused it.
soo you have tbi 350 heads on a 400-bored sbc? I would imagine that is not a good idea because of the steam hole thing and also compression ratio/ports/etc



your intake gaskets, how well did you do those
And what temp is it in morning vs day vs night, maybe youre hitting more moisture from warm engine that cools down multiple different times dew points all that jazz
 

L31MaxExpress

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soo you have tbi 350 heads on a 400-bored sbc? I would imagine that is not a good idea because of the steam hole thing and also compression ratio/ports/etc



your intake gaskets, how well did you do those
And what temp is it in morning vs day vs night, maybe youre hitting more moisture from warm engine that cools down multiple different times dew points all that jazz

The TBI heads work very well on a 400 doing truck things. Built one with a Comp 260 cam. ALOT more power than the stock 1-ton 350.

If the oil is not milk shake, IMO it is just moisture from short trips that are not allowing the moisture to boil off.
 

Deadman walking

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soo you have tbi 350 heads on a 400-bored sbc? I would imagine that is not a good idea because of the steam hole thing and also compression ratio/ports/etc



your intake gaskets, how well did you do those
And what temp is it in morning vs day vs night, maybe youre hitting more moisture from warm engine that cools down multiple different times dew points all that jazz
Yeah a 400 small block. pretty much a 2 barrel on a 400.

The steam holes,They're fine actually doesn't really effect it. Unless it pushing steam up through the intake.

Seems to run fine to me gets better gas mileage than the 350 did.
 

Schurkey

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They used to say that a 400 that usually ran faster than 3K rpm (race engines) didn't need steam-holes because the water pump flow would move the steam pockets as fast as they were created. If you're not generally at 3K or above, your engine is in danger of localized overheating due to steam pockets.

I'd guess the milky condensation is dripping down from the air cleaner riser nipple that's connected to the PCV system fresh-air inlet hose. Not enough PCV flow, or too-much blowby. The crankcase fumes 'n' condensation are flowing backwards through that hose into the air stream.

A higher-temp thermostat could help vaporize that moisture better. But unless the engine runs cool, that's not a "real" solution.
 

AuroraGirl

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Im not very knowledgeable on the head situation but The issue 400s have was because the heat near coolant passages and the lack of a good pathway meant hot, which meant steam, which meant not cooling anymore. Idk how stock TBI heads work, but if you dont have this provision then you are in danger is what I would be understanding. (Correct me if im wrong) maybe turning the fan and pump faster with a smaller pulley...? But not to overspeed of course.

also i would check on that crankcase ventilation you need an inlet and a controlled outlet (valve) on opposite corners if possible (back left, front right) on the valve covers
That inlet then goes to your ... air cleaner? Does the TBI tb use a port or does it port to the air cleaner?
 

Schurkey

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The issue 400s have was because the heat near coolant passages and the lack of a good pathway meant hot, which meant steam, which meant not cooling anymore.
Not exactly. The big deal with the 400 was that the cylinders were "siamesed"; there's no opening between the cylinder barrels that all the other SBCs have.

Any steam generated around the cylinder barrel on a non-400 just flows "up" and around the cylinder barrels, where it bubbles into the cylinder head through existing holes in the deck surface, head gasket, and head. Steam generated in a 400 without "steam holes" in the head and gasket, is trapped by the lack of passages around the cylinder barrels, leading to less cooling, even more steam. Until the steam pocket gets so big that it flows all the way to the back of the block and around the back of the rearmost (#7 or #8) cylinder.

Thus the "steam holes" in the deck between the joined cylinders, head gasket, and cylinder head that allow the steam to rise into the head without building-up into a giant bubble that has to flow all the way to the rear of the block.

also i would check on that crankcase ventilation you need an inlet and a controlled outlet (valve) on opposite corners if possible (back left, front right) on the valve covers
That inlet then goes to your ... air cleaner? Does the TBI tb use a port or does it port to the air cleaner?
The trucks, at least, use an air-cleaner riser between the throttle body and the air cleaner. The fresh-air inlet for the PCV system connects to the air cleaner riser.
 

AuroraGirl

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Not exactly. The big deal with the 400 was that the cylinders were "siamesed"; there's no opening between the cylinder barrels that all the other SBCs have.

Any steam generated around the cylinder barrel on a non-400 just flows "up" and around the cylinder barrels, where it bubbles into the cylinder head through existing holes in the deck surface, head gasket, and head. Steam generated in a 400 without "steam holes" in the head and gasket, is trapped by the lack of passages around the cylinder barrels, leading to less cooling, even more steam. Until the steam pocket gets so big that it flows all the way to the back of the block and around the back of the rearmost (#7 or #8) cylinder.

Thus the "steam holes" in the deck between the joined cylinders, head gasket, and cylinder head that allow the steam to rise into the head without building-up into a giant bubble that has to flow all the way to the rear of the block.


The trucks, at least, use an air-cleaner riser between the throttle body and the air cleaner. The fresh-air inlet for the PCV system connects to the air cleaner riser.
cool lol, so then a tbi head on a 400 needs to be made to have a steam port and the gasket too?


in terms of his issue with the condensation, i would make sure the PCV hoses are suitable for the application and arent collapsing and the valve is a ac delco for... hmm.. probably a 78 400 Id think tbh. But The inlet being different I guess idk lol
 

95burban

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The milk is caused by the crank case vapor from the tube that goes from the valve cover to the spacer under the air cleaner. If the motor sat for awhile it could go away after the rings seat again or the ol 400 might be a little worn. If you let the truck idle with the oil cap off the valve over and there is a great deal of vapor coming out then that’s the issue. I see it quite often. Don’t worry about it, run it.
 
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