Did I toast my 340?

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pauls340

pauls340

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Cruised Woodward Wed nite and the Demon overheated in the parking lot. Got it home, changed thermostat, gasket, rtv, added better hose clamps and done for the nite. Engine has run hot for 3-4 years but not on the gauge. Went to start it this morning, it cranked but didn't start; floored it 4 or 5 times and got it started. Went around the block, popped the hood and there's a mix of oil and antifreeze on the intake next to the crossover opening, see pic. Did I blow an intake gasket because it's so hot? If I drive it tomorrow, could this toast the engine? 2cents please.
340 Intake.JPG
 
Or head gasket. Do a compression check on it and see if you have leakage. If it overheated, it could have blown a head gasket. Is this mixture on the dipstick or in the oil pan? I wouldn't drive it until you figure out where the crud is coming from
 
That area of the intake is so far from coolant that obviously something not good is up.

Here's my first take on it.
Blown head gasket sucking coolant into a cylinder close by and since it seems to be coming out right where the crossover is (that burned looking spot on the intake), the gasket is trashed right there letting oil into that crossover where it's getting mixed with coolant from the exhaust.

They may be mixing right there where they both get by that burned gasket and may not have started mixing in the motor yet. (much) :D

My bet would be a blown head gasket on cylinders 3 or 5 and the spark plug for one of those cylinders may even confirm it.

As already mentioned, a compression test is in order to confirm it.
 
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It could get worse if it's a cracked head. The 2 exhaust ports in the middle, which includes the one with the crossover, are already concentrating heat there. But a blown head gasket between the middle two cylinders is more common than on the end ones.
 
Locomotion said:
It could get worse if it's a cracked head. The 2 exhaust ports in the middle, which includes the one with the crossover, are already concentrating heat there. But a blown head gasket between the middle two cylinders is more common than on the end ones.
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I think he has a blown head gasket AND a leak at the crossover letting the two fluids mix right at the crossover leak.
That's what it looks and sounds like to me anyway.

(Oil pushing up through the burned gasket then mixing with coolant in the exhaust from the blown head gasket and both coming out together)
 
TrailBeast said:
I think he has a blown head gasket AND a leak at the crossover letting the two fluids mix right at the crossover leak.
That's what it looks and sounds like to me anyway.

(Oil pushing up through the burned gasket then mixing with coolant in the exhaust from the blown head gasket and both coming out together)
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The head gasket could possibly be blown near the oil feed passage for the rocker arms...
 
Let's all jump to the worst conclusion!
To me, it looks like coolant has leaked out of the manifold somehow. Bad intake gasket maybe? The oil could be from the valve cover gasket or the breather. Or is there really any oil there? It could just be cooked antifreeze near that exhaust passage. I'd clean everything off and monitor the area closely. These might just be external leaks.
 
69_340_GTS said:
Let's all jump to the worst conclusion!
To me, it looks like coolant has leaked out of the manifold somehow. Bad intake gasket maybe? The oil could be from the valve cover gasket or the breather. Or is there really any oil there? It could just be cooked antifreeze near that exhaust passage. I'd clean everything off and monitor the area closely. These might just be external leaks.
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The problem with part of your theory is that there isn't supposed to be coolant anywhere near that area, and instead of thinking the head is busted through to the cooling jacket causing coolant to come out where it is I'm going for failed gaskets.
I'd even bet ya 10 bucks via Paypal that I'm right. :D

There is ZERO explanation for coolant leaking where it is except a 1.Busted head or 2.Intake and head gasket both, and I'm going with gaskets.

I get what you are saying though, because I see it all the time.
"OH, low on oil?"
"That could be a big *** hole in your oil pan where a rod is hanging out"

I think people just like to jump in and tell ALL the possible things they know, instead of the likely possibilities based on symptoms.
 
this would be about the time where I would go super deep in debt. Well honey I have to take the heads off any way. Mine as well buy new heads, different cam, etc.
 
Maybe it's just a trick of the camera. But are those lifters heat scored? It looks like some serious browning on the bottom of them there.

There's something going on. Going to have to tear the whole thing down me thinks.
 
The dark color on the bottom of the lifters is normal varnish build up. Remember the OP said the engine has ran hot for the last 3-4 years so this is not a fresh build. Start with removing the heads and inspect the head gaskets. This is the first step you need to take. Then act accordingly.
 
skep419 said:
this would be about the time where I would go super deep in debt. Well honey I have to take the heads off any way. Mine as well buy new heads, different cam, etc.
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I have actually used that before. It works.
 
harrisonm said:
I have actually used that before. It works.
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This engine was build 24 years ago just before I bought the car. It was built slightly bigger than my original Demon340 I bought in 1971. I really want a pure stock built 340 so it might be time to call Koffels Place or another builder. My strong running 340 has got to be worth something as trade?
 
I don't think so. I bought a new Intake gasket set and I would hate to put it all back together and drive it tomorrow and break it badly.
 
pauls340 said:
So i'll highjack my own thread; what else can you tell is going on with this engine? Burn this, burn there, etc etc ??
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Show me that left side intake gasket (both sides of the crossover port)
My money is on the theory that the coolant in there right now seeped in after you last shut it off from the same place it came up on top of the intake.
Bet you anything the gasket looks trashed at the crossover, and at least cylinders 3/5 (I guess that would be 4&6:D) have a blown out ring on the head gasket.
(AND the either one or both 4&6 plugs are nasty and look different than the others.
Also note how the crossover port is wet inside, and there isn't coolant anywhere near there to run down from pulling the intake, as it's to centralized in the block and there is only coolant at the ends of the intake and block.
If it came from pulling the intake it would be at both ends of the engine and not only in the center.

I think you got REALLY lucky and just need to replace the head gaskets and intake gaskets.
Well, that and oil and filter obviously.
Paper towels will soak up that coolant puddle, but just let it soak it up and not rub all around in there or you'll get paper shed all in there.

OH, and Roy is correct about that stuff on the lifters being deposits and not heat discoloration.
You can prove it to yourself if you want by wiping it off with some carb cleaner or whatever and a cloth. (you can't wipe of heat discoloration)
 
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TrailBeast said:
Show me that left side intake gasket (both sides of the crossover port)
My money is on the theory that the coolant in there right now seeped in after you last shut it off from the same place it came up on top of the intake.
Bet you anything the gasket looks trashed at the crossover, and at least cylinders 3/5 (I guess that would be 4&6:D) have a blown out ring on the head gasket.
(AND the either one or both 4&6 plugs are nasty and look different than the others.
Also note how the crossover port is wet inside, and there isn't coolant anywhere near there to run down from pulling the intake, as it's to centralized in the block and there is only coolant at the ends of the intake and block.
If it came from pulling the intake it would be at both ends of the engine and not only in the center.

I think you got REALLY lucky and just need to replace the head gaskets and intake gaskets.
Well, that and oil and filter obviously.
Paper towels will soak up that coolant puddle, but just let it soak it up and not rub all around in there or you'll get paper shed all in there.

OH, and Roy is correct about that stuff on the lifters being deposits and not heat discoloration.
You can prove it to yourself if you want by wiping it off with some carb cleaner or whatever and a cloth. (you can't wipe of heat discoloration)
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Thanks everyone. I now have two really known local engine builders on my list. I may as well pull the heads and have them checked out. Thanks again, Paul
 
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