Jayarr
New Member
Real car guys use the term.
440 engine making a noise that sounds like an exhaust leak, but no leak is found
- Thread starter DC118us
- Start date
DC118us
Member
I’m going to level set. Reassemble everything and do a compression check. Then pull the exhaust manifold if compression is ok. Replace oil and go from there
DC118us
Member
Update:
re-assembled the valve train, torqued properly. Performed a compression test on 2, 4 and 6. all came back equal, so that was hopeful.
I pulled the exhaust manifold and sure enough. bad spot on the gasket at # 4. So that's the noise I'm sure.
I happen to have 1 manifold gasket, but when I started to torque the bolts/nuts to 30 ft/lb, the rear nut/stud stripped. then one of the long nuts did the same, so I gave up and ordered some replacement parts for that. Now I wait. I bought the 68-71 C body kit, which isn't exactly correct, but has what I believe are enough long bolts to do the one manifold.
Thanks for all the advice, I'll update once I get the kit and install it. The fuel in the oil is a different matter...
re-assembled the valve train, torqued properly. Performed a compression test on 2, 4 and 6. all came back equal, so that was hopeful.
I pulled the exhaust manifold and sure enough. bad spot on the gasket at # 4. So that's the noise I'm sure.
I happen to have 1 manifold gasket, but when I started to torque the bolts/nuts to 30 ft/lb, the rear nut/stud stripped. then one of the long nuts did the same, so I gave up and ordered some replacement parts for that. Now I wait. I bought the 68-71 C body kit, which isn't exactly correct, but has what I believe are enough long bolts to do the one manifold.
Thanks for all the advice, I'll update once I get the kit and install it. The fuel in the oil is a different matter...
No exhaust gaskets from the factory! Although many gasket kits might include them, not OEM used. Cast iron to cast iron.
The gaskets MIGHT be used as an aid if the manifold might be warped, but that would be the only reason. Steel headers need gaskets due to the different expansion rates of the two metals, plus the fact most of the welds on the flanges were not always as smooth as they would need to be. The quality of the soft gaskets that came with them would eventually blow-out, though. The later "black" gaskets with internal reinforcements lasted much better.
Just some thoughts,
CBODY67
The gaskets MIGHT be used as an aid if the manifold might be warped, but that would be the only reason. Steel headers need gaskets due to the different expansion rates of the two metals, plus the fact most of the welds on the flanges were not always as smooth as they would need to be. The quality of the soft gaskets that came with them would eventually blow-out, though. The later "black" gaskets with internal reinforcements lasted much better.
Just some thoughts,
CBODY67
DC118us
Member
I had the manifold off recently and removed the heat control valve completely and had the holes welded shut.
DC118us
Member
Hmm, I didn't know that. Was there some sort of sealer applied between the parts? When I removed it to remove the control valve, there was a gasket in place, which is why I replaced it.
No gaskets between the cyl head and exhaust manifold. Only seal is between the exhaust manifold flange and the exh pipe, which is a beaded steel shim gasket.
Cast iron seals against itself just fine, as long as the two surfaces are flat and not warped.
At a seminar given by a Holley engineer, he stated that gaskets make up for poor machine work.
Put the center bolts in, then work in a circular fashion toward the ends, just like torquing a cyl head or intake manifold.
The fact a gasket was between the exh manifold and the head means that "somebody has been there before".
CBODY67
Cast iron seals against itself just fine, as long as the two surfaces are flat and not warped.
At a seminar given by a Holley engineer, he stated that gaskets make up for poor machine work.
Put the center bolts in, then work in a circular fashion toward the ends, just like torquing a cyl head or intake manifold.
The fact a gasket was between the exh manifold and the head means that "somebody has been there before".
CBODY67
DC118us
Member
Oh that’s interesting. My 75 exhaust manifold had a gasket between the head and manifold, but has the ball and socket style connection to the exhaust system, not requiring a gasket. Possibly a different set of manifolds?
Did the gasket you removed extend up beside the valve cover, or was it just for the holes in the head? Reason I ask that is that an evolving issue with the additional underhood heat of emissions engines and the closeness of the exhaust manifolds to the valve cover gasket, it might have been that such a taller gasket was worked into the 1974 platform re-design? After the orange solid silicone gaskets didn't help too much in the integrity and sealing of the valve cover gaskets.
The ball-joint lower pipe connection was probably a "Formals" re-design too, I suspect. Prior to that, all of the exhaust manifold flanges were flat. The ball joint connection was where the lead pipe attached to the under-car pipe going to the muffler.
Just some thoughts,
CBODY67
The ball-joint lower pipe connection was probably a "Formals" re-design too, I suspect. Prior to that, all of the exhaust manifold flanges were flat. The ball joint connection was where the lead pipe attached to the under-car pipe going to the muffler.
Just some thoughts,
CBODY67
DC118us
Member
The gasket did just cover the exhaust holes. I suspect you’re correct about this being a formal redesign!
Yes, no gaskets from the factory. It's been my experience that it isn't a matter of IF the replacement gasket burns out, it's WHEN it burns out.
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