slant 6 problem

I need someone to confirm what I believe I already know. I have a 1976 Dart Sport with a /6 engne. Havent had it long but I believe it either has a crack in the head or a blown gasket. I have no water in oil or oil in water but It smokes a light gray when it is cold.When it warms up it goes away. The exhaust is real hot when running. has some loss of power, rough idle. I think it is blowing some anti freeze out the exhaust manifold. Can someone help me with this. Are these /6 known for this. Do you think it is a gasket or the head.

How do your plugs read?

crewchief said:

How do your plugs read?

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plugs look fine

So, on chalky appearance on the ground strap and center electrode?

Compression test, listen for air in the exhaust or intake, bubbles in the radiator. They are not known for head gasket issues, but it's a 40+ year old car.

When I suspect antifreeze in the exhaust, I swab my finger around the inside of the tailpipe and taste my finger, looking for the telltale sweetness.
Make sure you are not confusing the gray smoke for water vapor which is a normal by-product of combustion. The smoking is always more pronounced with a cold engine, with a cold exhaust system, at cold ambient, and on high-humidity days.

AJ/FormS said:

When I suspect antifreeze in the exhaust, I swab my finger around the inside of the tailpipe and taste my finger, looking for the telltale sweetness.
Make sure you are not confusing the gray smoke for water vapor which is a normal by-product of combustion. The smoking is always more pronounced with a cold engine, with a cold exhaust system, at cold ambient, and on high-humidity days.

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Rough idle,,, when was the last time the valves were adjusted?
Also the mid 70’s cars have yards of vacuum hose under the hood. Check for cracked or missing vacuum hoses.
Agree that slants do not typically have head gasket issues.
Can you estimate how much antifreeze is being lost per 500 miles?
My guess on that issue is a leaky radiator or water pump,,,

my68barracuda said:

Rough idle,,, when was the last time the valves were adjusted?
Also the mid 70’s cars have yards of vacuum hose under the hood. Check for cracked or missing vacuum hoses.
Agree that slants do not typically have head gasket issues.
Can you estimate how much antifreeze is being lost per 500 miles?
My guess on that issue is a leaky radiator or water pump,,,

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not sure of antifreeze loss. just replaced the radiator with a new one but this has been going on before that. checked for hose cracked saw none. has loss of power. will check tailpipe. thanksfor the response.

I agree with what has already been said.

Since the car is new to you I would start with the basics. You can assume nothing until you verify it. Buying an old car is like buying a box of chocolates, right Forrest?

Do a compression check and write down the numbers. That will tell you the general condition of the rings, valves, head gasket, etc. Remove all the spark plugs and prop the throttle plate open with a screwdriver down the carb throat. The numbers should ideally be within 10% of each other. If you don't have a gauge you can borrow one from one of the larger auto parts store chains. 2 adjacent cylinders with very low numbers is most likely a blown head gasket.

While you are at it rent a cooling system pressure tester. Good for checking if in fact there is a leak in the system. You can also check the rad cap with the same tool.

Look at the condition of the rotor and distributor cap.

Check for timing chain stretch.

Adjust the valves.

Check the timing correctly with a light and set it for 8-10 degrees BTDC.

Collect all the data as you go along and write it down.

trudysduster said:

plugs look fine

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Boy, does that ever tell us a whole heck of a lot, like your exhaust could look fine but be rusted as snot on the inside and you not knowing it. Follow advice given. Good Luck

69a100 said:

Boy, does that ever tell us a whole heck of a lot, like your exhaust could look fine but be rusted as snot on the inside and you not knowing it. Follow advice given. Good Luck

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Well what did you want me to say. I just put the plugs in not too long ago and by looking fine means they look about like they did when I put them in new. I said I have not had this car long. But I didn't mention that when I bought this car I replaced the plugs, wires, cap rotor, carb and a few other things a person would do. So, like I said. the plugs look fine.

I once put a brand new set of plugs in an old Sunfire. And a few days later she lost a cylinder. I isolated the bad cylinder, pulled the plug out, and
"it looked fine".
But I'd been fooled a time or two in 52 years of working on cars, so I pulled a different plug out, and it too
"looked fine".
So I swapped them around, and now the dead cylinder followed the "fine looking plug".
So I put a brand new " fine looking plug" in there and now had 4 cylinders again.
So then I went and studied that no good, but "fine-looking" plug. And with a magnifying glass I found a hairline crack in the porcelain. That "fine-looking" plug ran perfectly for a few days and then just like that, it cracked the poecelain and that "fine-looking" plug was 100% garbage .
Two things I have learned in my life;
1) never trust a fart, and
2) never overlook the obvious.

IDK if your problem is a plug or not, but if you isolate the bad cylinder, and swap a different plug in there and the problem goes away; then,I'd say that is all the proof I need.
And that just leaves the why of it.
In my case it was detonation, because it later cracked other plugs. actually broke them,and swallowed the pieces.
As for your slanty, IDK.

BTW, not trying to be a jerk, just saying you can't always eyeball a plug and know that it's fine. I did not comment earlier, because there's always a chance that you were an ace-mechanic and knew what fine meant. So I didn't want to embarrass myself too early in the thread,lol.
I like to say things like ;
"they looked fine to me", or;
"since they're brand new, I assumed they were fine."
That way it doesn't hurt as much when the Master Mechanic says " what's a fine plug look like?"
Then I can answer, "What do you mean", and nobody gets their feathers ruffled.
Happy Hunting

Light grey, dark grey and black are all fuel. Oil is very light blue. Coolant is white.