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Hey all!
I recently had my exhaust redone but I'm still getting fumes in the cab.
I suspect it's coming from the exhaust manifold or if I'm really lucky, maybe it's just the manifold gaskets?
Can someone advise me on how to check for leaks?
I have a '66 D200 with a 318 and 79k original miles.
Also, if I have to buy new manifolds, does anybody know where to get them?

You should see black where exaust is coming out, you should also by able to hear it. When I had the same problem the flange gasket was leaking. Also after you find leak make sure you have no holes in firewall, gear shifter gas pedal.

Hold a thick rag on the tail pipe until pressure builds up, You will hear where it coming from or as GMAN said, should be able to see the black soot. Might need a partner to pinpoint location.

pwadventurer wrote:Hold a thick rag on the tail pipe until pressure builds up, You will hear where it coming from or as GMAN said, should be able to see the black soot. Might need a partner to pinpoint location.

My wife and I actually tried that last night. I couldn't hear a thing. Too many years playing loud guitars, Harley's and working for an airline I guess.
I did notice however that one of the exhaust manifolds appears to have some kind of generic or homemade gasket. I'm hoping thats the culprit. I don't know where else exhaust could be coming from?

Have you tried running the engine at night in complete darkness? A leak at/near manifold could show flame.

Bucky

712edf wrote:Have you tried running the engine at night in complete darkness? A leak at/near manifold could show flame.

Bucky

I tried that last night also. I can't see or hear anything but man, I sure can smell it!
It's gotta have the windows down and wind wings open bad.
pwadventurer mentioned to look for black soot but I power washed the engine right after I got it. I was chasing down an oil leak at that point.
I'm going to order new gaskets and try that first.
Hopefully I'm not dealing with a cracked manifold. From what I've found searching the net, theres not much out there for a poly 318.
Any insight as to what I should be looking for once I get manifold off or gasket recommendations, would be greatly appreciated.

Poly manifolds commonly crack either side of the center dump. They also leak around the shaft for the heat riser valve and the pipe to manifold gasket. U should also look at the entire pipe and muffler. Manifold cracks are easy to see, use a flashlight.

I hate to recommend headers, but they are out there for the poly, actually some nice ones.
It shouldn't be too hard to find stock poly manifolds, or possibly have yours welded up if that's the case.

Bucky

Well since my original post, things took a turn for the worse and I now have a bigger problem than the manifold leak.
Monday morning I got in the truck, turned the key and KA-BOOM!!!!!!!
My brand new muffler exploded like a cannon and peeled apart like a banana. Besides scaring the living crap out of me, it rattled all of the windows in the houses nearby and caught the attention of every neighbor who hadn't left for work yet. It also knocked about 50 years worth of road dirt and a couple hornets nests from underneath the bed. It looked like someone had taken a 5 gallon bucket of decomposed granite and threw it under the truck.
Now what?

OK, 1st you got exhaust smell (in cab), then muffler explodes??

Sounds like something was clogged downstream.

Who did this exhaust work? That seems to be when the smell began based on what I've read.

Bucky

712edf wrote:OK, 1st you got exhaust smell (in cab), then muffler explodes??

Sounds like something was clogged downstream.

Who did this exhaust work? That seems to be when the smell began based on what I've read.

Bucky

When I bought the truck, the exhaust in the cab was much worse. The exhaust pipe and muffler was riddled with holes and loud as hell.
I had that replaced at a nearby muffler shop that has nothing but good reviews but there is still exhaust coming into the cab.
I'm pretty sure its coming from the exhaust manifold on the passenger side. I was planning to go ahead and pull it off, inspect for cracks and if none, plug up the heat riser gizmo and install new gaskets.
My first thought was that gas(from the carburetor) had flooded and caused the explosion. It detonated as soon as I turned the key, just like in the movies! I had a shop nearby inspect it but they say the carb seems to be working fine and they also believe that something plugged it up. It seems to me that it would have to run for a while for pressure to build up to cause something like that.
For what its worth, the truck runs really rich and I was planning on addressing that but I've been trying to focus on one thing at a time. I don't want to give up. I'd like to save this truck from the scrap heap but It's been extremely draining and I'm reaching the end of my financial rope.
Ive already spent a ton of cash rebuilding the front end and suspension.
Any help is truly appreciated.

Unburned fuel in your exh pipe and muffler from running rich. Sat just the right amount of time to evaporate to a perfect air/fuel ratio. One plug fired when u turned the key, exh valve was slightly open and it went off like a bomb. Great timing and rare alignment of all the perfect parameters and that's what happens. Sucks when it was a new muffler!

I did crap like that intentionally, rolling down the highway in the freeway tunnel here, back in the 70's. Flame shooting out the exhaust pipe and massive boom scared the *#%^ out of the other drivers. When it sheared all the bolts holding the flex plate to the torque converter I quit doing it!

PwrWgnDrvr wrote:Unburned fuel in your exh pipe and muffler from running rich. Sat just the right amount of time to evaporate to a perfect air/fuel ratio. One plug fired when u turned the key, exh valve was slightly open and it went off like a bomb. Great timing and rare alignment of all the perfect parameters and that's what happens. Sucks when it was a new muffler!

So, where do you think my problem might be? Is it the carb or simply a carb adjustment to lean it out?
What would cause unburned fuel to get into the tailpipe?

Many possibilities. Usually involves several, incl carb, adjustments, timing, misfiring cyls, burned valves, eroded seats.
If the engine is original and never had hardened valve seats installed, unleaded gas destroys the original seats.

PwrWgnDrvr wrote:Many possibilities. Usually involves several, incl carb, adjustments, timing, misfiring cyls, burned valves, eroded seats.
If the engine is original and never had hardened valve seats installed, unleaded gas destroys the original seats.

It's the original engine with 79k miles. It runs smooth, no stalls or hesitations. It starts every time on the first try, it seems solid and there's no leaks(anymore). I was planning to address the carb, lean out the air/fuel mixture and give it a basic tune up but when this happened, it kinda change my plan.

A guy named Bruce Toth on the other sweptline forum (www.dodgesweptline.org) has poly exhaust manifolds for sale, just listed yesterday.
His number is 724-290-2497

Bucky

712edf wrote:A guy named Bruce Toth on the other sweptline forum (http://www.dodgesweptline.org) has poly exhaust manifolds for sale, just listed yesterday.
His number is 724-290-2497

Bucky

Thank you for the contact. I hope to have some time this weekend to take a good look at mine.