I'll try to cut to the chase.

I have a slant 6 225 in my 71 Dart swinger - it was recently rebuilt, not by me or anyone I know.

We had it running for the first time last week - ran okay after it had just had a cold and hot valve adjustment. Ran good enough to drive it around the block a couple of times for its first test drive. My mechanic and I decided he'd come back and do some final adjusting the following week.

He comes back yesterday and sees that there's a little oil leaking from the rear of the head and we both shuddered when we remembered that we had to loosen the left rear cylinder head bolt last year when we were checking for an oil flow problem. So in other words the car had now been run several times with that left rear bolt pretty loose (okay big goof). So he tightens the bolt down and continues with what we thought would be the final tweaking on the engine only now when he starts the car he can't keep in running without keeping his foot on the gas - runs pretty good with the foot on the gas but it dies when he takes it off. The only thing we had done at that point was tighten down that rear bolt. He also saw the radiator fluid gush out of the radiator unexpectedly (cap was off) he was just checking some radiator stuff too.

He checks various things - he checks the timing, puts new spark plug wires on. Still the car will not stay running without him keeping his foot on the gas.

Does a compression check and a leak down test and thinks maybe he hears a leak from the rear of the head (near the location of the formerly loose head bolt.)

He also sees that the spark plugs are getting exhaust dirt/soot on them after running the car briefly.

Anyway, I'm not a mechanic and I know I've left out some of the details, but his conclusion at this point is that the head gasket is likely damaged from that rear bolt being loose. Does this sound like a pretty good conclusion at this point?

Thanks,
Darcy

tighten all head bolts to spects..
just start it up and observe the temp guage and idle ..if it idles OK, and temp does not go up..ur OK
check oil 2C if there H2O in it..blown head gasket if there is..it will look gray 2milkey
if no problem there
then let cool remove rad cap start and look for bubbles...if there r , thats blown head gasket with the gases transfering into the H2o content rad.

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slant six's RULE!
http://www.usajon.com

Oil looks okay.

(Temp gauge is currently broken and on my list of things to fix).

I'll have to try your radiator recommendation later.

Thanks!

yes. u need to fix the temp guage..it could $ave ur motor..
be well.

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slant six's RULE!
http://www.usajon.com

Many things can cause your engine to not run at idle... a vacuum leak being chief among them.

Any loose vacuum hoses?
Are the carb to manifold bolts tight?

How about the infamous vacuum leak between the manifold and the head? A little carb cleaner spray will detect that soon enough.

Also possible for junk to settle into the fuel bowl of the carb, thus plugging all the little passageways in there. My valiant did that after a brief bumpy ride... which shook up all kinds of contaminates. Wouldn't idle after that, had to keep it at 1/4 throttle to keep it running. I had to tear down the carb to restore it to smooth idle after that.

- Mac

So do people think it was just a coincidence that we tighten that rear head bolt and the car suddenly would not hold an idle without keeping our foot on the gas? Seems like a coincidence to me....

Thanks

Hard to say with out looking & testing all the items that have been listed. Just go down through the list, sooner or later you will find the problem, or problems.

Where the car has not run for an extended length of time, I would not rule out any fuel delivery problems. So add to your list to check fuel pump out put, fuel filter contamination, fuel line restriction including the soft lines for dry rot from today’s crappy gas, and of course the carburetor for crud, stuck or mal adjusted floats, etc. Once a carburetor has sat un used for a while such as over winter there is a good chance it need a rebuild.

So before you spend any money on parts, work smart and test out everything first.

One other tid-bit: Make sure that the valves were adjusted correctly remembering that starting at the front of the engine the first valve is an exhaust. So the first three cylinders are E I, E I, E I, the last three cylinders the valve arrangement reverses starting at #4 cylinder it goes intake exhaust, I E, I E.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Here's an old trick... pull the spark plug wire on the cylinder in question while the engine is running (be careful not to get zapped!). If the engine slows down or begins to run rough, then you know that cylinder is working.

Not a very scientific check, but it does work.

I'm still betting on crud in your fuel bowl.

- Mac

Thanks! I'm making a list of things to check.

Thanks Mac - we'll check this stuff!

Why not loosen that bolt as before? and see if it fixes the problem.

I agree, that seems like a reasonable option to try.

Did you re-check the valve lash after tightening the head bolt?
Better yet...
Warm engine, retorque the head & re-adjust the valve lash... to the loose side of the settings.
DD

Hi Doc,
Thanks! I just spoke with my mechanic and we had come to a similar conclusion that you're saying. I just found out that his order of events was that he tightened the head bolt, then adjusted the valves and then attempted to start the car. I had initially thought he went straight from tightening the head bold to starting the car..... so it sure seems like the valves could be the ticket. I am hoping!

I just can't wrap my head around a "mechanic" setting valve lash on a slant 6 with the engine off. I suppose you COULD, but the (best) way to get the most accurate adjustment is with the engine at hot idle.

Besides, if it's not running during the lash adjustment, you don't get the "satisfaction" of hearing the clattering disappear as you go down the line.

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63 Valiant Wagon
225 - 4 bbl