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Old 09-29-2008, 02:11 PM
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Headgasket or intake leak?

Nothing but troubles on this re-rung 400. I wish now I fully rebuilt it. Upon startup there is a little bit of smoke moreso on passenger bank, which gets progressivly worse until both tailpipes are pouring white smoke.

On acceleration it leaves a huge smoke cloud. The oil is slightly milky but there doesnt seem to be any oil in the coolant. Im gonna run it and see if I can see bubbles in the rad here in a few minutes.

Any insight or will I be replacing gaskets again?

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Old 09-29-2008, 02:35 PM
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Quote:
Originally Posted by Nsomnia
Nothing but troubles on this re-rung 400. I wish now I fully rebuilt it. Upon startup there is a little bit of smoke moreso on passenger bank, which gets progressivly worse until both tailpipes are pouring white smoke.

On acceleration it leaves a huge smoke cloud. The oil is slightly milky but there doesnt seem to be any oil in the coolant. Im gonna run it and see if I can see bubbles in the rad here in a few minutes.

Any insight or will I be replacing gaskets again?
Milky oil is a surefire indicator that coolant's getting into the oil. Lots of ways that can happen. This is a very serious situation which will quickly take out expensive parts like bearings, pistons, cam and lifters.

If it starts on one side and progresses to the other, a good place to start looking is the intake to head gaskets allowing leaks into the ports and valley area. the combination of milky oil and steam smokey exhaust would lead me to start here.

Some others:

- Selecting parts can contribute to this. There are heads and manifolds that because of port placement variables can leak both vacuum and coolant.

- Bolts both head to block and intake to head that were not installed with sealer can be a source of water getting inside the engine.

- Machining operations of milling the heads or block can result in leaks in these areas.

- Porting can have this result by breaking into the cooling jackets either directly or by thinning the walls till they develop in-service cracks.

- Certainly normal cracking that's gone un-noticed can result in these problems. The SBC is quite given to cracks between the intake and exhaust seats, between the seats and the sparkplug and along the valve seat to chamber wall especially where the wall has been pushed back for a 2.02 valve. The 400 is really given to producing cracks where the Siamese cylinders vent coolant to the head. These are small holes that often plug up, this results in local overheating that causes cracks to both the head and block.

- Warpage to the head or block that prevents the gasket from making a tight seal.

Bogie
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Old 09-29-2008, 03:43 PM
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Quote:
Originally Posted by oldbogie
Milky oil is a surefire indicator that coolant's getting into the oil. Lots of ways that can happen. This is a very serious situation which will quickly take out expensive parts like bearings, pistons, cam and lifters.

If it starts on one side and progresses to the other, a good place to start looking is the intake to head gaskets allowing leaks into the ports and valley area. the combination of milky oil and steam smokey exhaust would lead me to start here.

Some others:

- Selecting parts can contribute to this. There are heads and manifolds that because of port placement variables can leak both vacuum and coolant.

- Bolts both head to block and intake to head that were not installed with sealer can be a source of water getting inside the engine.

- Machining operations of milling the heads or block can result in leaks in these areas.

- Porting can have this result by breaking into the cooling jackets either directly or by thinning the walls till they develop in-service cracks.

- Certainly normal cracking that's gone un-noticed can result in these problems. The SBC is quite given to cracks between the intake and exhaust seats, between the seats and the sparkplug and along the valve seat to chamber wall especially where the wall has been pushed back for a 2.02 valve. The 400 is really given to producing cracks where the Siamese cylinders vent coolant to the head. These are small holes that often plug up, this results in local overheating that causes cracks to both the head and block.

- Warpage to the head or block that prevents the gasket from making a tight seal.

Bogie
I dont remember sealer being used on the headbolts, but then again this is ALOT of steam/smoke.

No bubbles from the radiator but img onna rip the intake off quick and see what the gaskets look like.
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Old 09-29-2008, 04:54 PM
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The oil isnt as milky as I origionally thought, more of a gravy instead of chocolate milk.

Heres a picture of the intake manifold gaskets, according to my father they were reused twice (!!) so im replacing them now anyways. I still think its gonna be the head gaskets both blew.
You can see where water recently pooled making chocolate milk.

Sorry about the size, your gonna have to scroll.





Just rambeling trying to give more info for a solution: when I first fired it up and gave it some revs water leaked out inbetween the intake and head on the water port front drivers side. Thats alittle bit of faith I guess.
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Old 09-29-2008, 05:03 PM
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intake gaskets.........

Hi,first of all....NEVER...re use intake gaskets, always use black RTV on front and rear of engine where the intake seats. (not the cork gasket) i use about 1/4 inch bead of RTV,run the RTV up a little onto the side gasket. filling the corners, i always go up about 3/16 inch. tighten intake manifold in proper sequence.(if you dont know,check the book)
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Old 10-01-2008, 05:00 PM
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Quote:
Originally Posted by oldbogie
- Bolts both head to block and intake to head that were not installed with sealer can be a source of water getting inside the engine.

Bogie
I replaced theintake gaskets to no help so im looking for one last bit of advice before I rip the heads off.

I doubt both headgaskets would blow at the same time, could it be that since no thread sealer was used on any headbolts that itsleaking out of the bolts into the combustion chamber?

Do all the bolts have water flow or just the outer small ones? What should I ask for at napa?
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Old 10-01-2008, 06:03 PM
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Quote:
Originally Posted by Nsomnia
I replaced theintake gaskets to no help so im looking for one last bit of advice before I rip the heads off.

I doubt both headgaskets would blow at the same time, could it be that since no thread sealer was used on any headbolts that itsleaking out of the bolts into the combustion chamber?

Do all the bolts have water flow or just the outer small ones? What should I ask for at napa?
- Remove the heads and clean all surfaces. Throw a known good straight edge on the block and the heads and shine a light on the opposite side. If you see light at the interface measure the gap, anything more than .005-.007 inch should be grounds for milling the surface. The same procedure is done on the port sides of the heads and to the intake manifold.

- Take a piece of welding rod and probe all the head bolt holes in the block. Typically an SBC will be open on the bottom, but because of casting or machining errors this might not be true for all. The reason to this is avoid damaging the block in a blind hole at the next step.

- Since the torque values are given for a clean and lubricated bolt and bolt hole you want to pass a proper sized tap into the block to remove the gunk. The bolts should be wire brushed not run thru a die for cleaning. I use regular plumbers Teflon pipe joint compound to seal the bolts. This stuff is close to the resistance of oil lubed bolts so you can use standard torque readings. For holes that I know are open to the cooling jackets I apply a thin coating all the way down the bolt hole and a thin coating on the bolt. This insures that there will be a seal all the way down to the exposed end of the bolt. This type sealer doesn't harden so any extra pushed out the bottom of the hole is just mixed into the coolant. The reason for previously having checked for closed bolt holes is that you don't want extra sealer being pushed ahead of the bolt in these as if there is less volume between the bottom of the bolt and the bottom of the hole than there is sealer, hydraulic force will crack the block. So for these its a light coating only on the bolt's threads.

- A similar situation exists on the intake to head. Some of these bolt holes go into the water jackets and some to the oily interior. In both cases they should be sealed in the same way as head bolts.

Bogie
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