Blown head gasket or something else?

[Tonker1]

Righteo, so  just recently I go the engine running for the first time in 6 months and I've been enjoying the glory of sound that rumbles from a V8.

This morning I noticed when the engine was running that it was blowing a bit of white mist out the both exhaust pipes. The pipes are not connected, each pipe only serves its respective side of the engine.
I put my hand behind the exhaust and it came out moist.
After revving small drops of liquid spray out and mist gets thicker, engine attempts stalling after that.

From what I've read it seems like I've blown both head gaskets at the same time, is that even possible?
It seems strange for them both to go at the same time?
Is it hard to change the head gasket or just massively time consuming, or hopefully neither?!!!! I've haven't gotten that deep into the engine yet.
Would I be running the risk of damage to the engine if I let it run for 20 min to see if the mist goes away?

Another thing, I only have tap water in my radiator at the moment because I've been flushing it out, which would mean I wouldn't get the impressive smoke cloud from antifreeze boiling over.

[1970 RT Challenger 1970]

About 20 years ago I had a V8 1/2 ton truck with a blown head gasket.

Ran Hot, No Power, No Balls, Felt like you were driving a 3 cylinder, could barely make it to 60 mph.

[Bullitt-]

Probably the moisture your seeing is condensation, if you just warm up an engine you tend to get a lot of condensation in the exhaust so the next time there will be more water than if were ran at operating temperature.   

[67vertman]

Probably the moisture your seeing is condensation, if you just warm up an engine you tend to get a lot of condensation in the exhaust so the next time there will be more water than if were ran at operating temperature.   

 

Very unlikely that you blown both head gaskets.  You should run a compresion test to be sure.

[Skunkworks Challenger]

I agree, not likely both head gaskets would blow at the same time.  Even so, if the engine is off water can leak into the combustion chambers but once the engine is started the flow goes the other way and would force coolant out of the cooling system.  Most like condensation as Bullitt suggested.

[moparmaniac59]

Have you checked your coolant? Does it look milky (oil/water mix)? You may want to also do a pressure check on the coolant system as well as the compression check. Have you pulled the dipstick and looked at it to see if there is any water in the oil pan? Hopefully it's just condensation.


                                                                    Matt B.

[MEK-Dangerfield]

An amateur like me would drain the water out of the radiator and put in anti-freeze. That way, if it is a blown head gasket, the sweet smell will tell you and everyone around you that you blew a head gasket.   

[Tonker1]

Filled her up with antifreeze today and let it fun for 30 min, the white mist was back after I started the car and then it suddenly stopped after about 5min. I figure its just built up moisture inside the exhausts from its 6 stationary months. Popped off the valve cover and the oil looked fine, no milky white build up! Just to make sure I got a compression tester which I'll cycle though all the cylinders tomorrow. If it's all good after that it'll be celebration time!

As far as I'm aware the compression ratio will be what it came out of the factory in my 72 engine.
Does anyone have a ball park figure as to what Psi the compression tester should read? That was probably a fairly stupid questions due to all the variables, but it can't hurt to ask.

Thanks for all the advice.

[moparmaniac59]

You didn't say what your engine is, but I think at a minimum it should be 100 psi. The main thing to look at is make sure the compression is fairly even between cylinders. In other words if you had 7 cylinders all at 125 psi and one at 100 psi, there might be a problem even though all of them are not below minimum specs.


                                                                        Matt B.

[MEK-Dangerfield]

You didn't say what your engine is, but I think at a minimum it should be 100 psi. The main thing to look at is make sure the compression is fairly even between cylinders. In other words if you had 7 cylinders all at 125 psi and one at 100 psi, there might be a problem even though all of them are not below minimum specs.


                                                                        Matt B.

   

I think Matt has the right idea. But I'm thinking you will be OK with your compression check.

[burdar]

I figure its just built up moisture inside the exhausts from its 6 stationary months.

Water is a by-product of combustion.  The entire time the engine is running, it's pumping water into the exhaust.  If you don't run the engine up to operating temp(very short drives around town) the exhaust never gets hot enough to burn out the water.  It sits in the exhaust and rots it out.  That's what you are seeing.  The water build-up isn't from the car sitting for 6 months.

To get more of the water out of the exhaust, add a weep hole to the lowest part of the mufflers on the back side.  1/8" holes are big enough.

[67vertman]

Watch new car in the morning, almost all of them are putting water out the tailpipe!

My 318, almost 40 years old and never rebuilt had compression of 125 - 135. 

[Tonker1]

It's a 1972 340 so the compression ratio should be around 8.5:1

If you don't run the engine up to operating temp(very short drives around town) the exhaust never gets hot enough to burn out the water

Burdar, what you said about the engine never properly warming up makes sense. As I've been trying to fix the engine bay wiring harness/fuelling issues/ carb issues all at the same time so the engine has ran sporadically for 1-2 minuets at a time maybe 20, 30 times over the past couple months. Now that it runs, its finally had a chance to blow off some steam (literately), it should all be fine.

The main thing to look at is make sure the compression is fairly even between cylinders

Tomorrow I'll check compression for consistency across the pistons. What I was trying to ask about the psi before, could a consistently low psi be a symptom of another issue?
I'm guessing it's best to let the engine warm up first then test so there are less variables in the results?

[Tonker1]

Completed the compression check, it ranged from 120-130psi which seems to reasonable amount of give. So, dodged a bullet on that one!

Thanks for all the advice and comments, it really helped and know that the engine is fine it's time to move onto the next project; wheels, disc brakes and seatbelts!

[67vertman]

Those are good compression numbers!

Glad to hear that it is not your motor.