Exhaust leak ??

70 440 stock exhaust manifolds . Loud exhaust leak on passenger side. Sounds like it's just one port. There are no scorch marks or any signs of leak. Plugs are all tight. Manifolds still tight. Defiantly coming from the passenger side head area. Took the valve cover off because it almost sounds like a bent push rod or broken rocker arm. But everything checks out. Tried using a stethoscope and still can't pinpoint it. No oil or bubbles in the coolant. I do hear a hissing sound from the passenger side if I click the motor over without starting it. No cracks in the exhaust manifold. My only thoughts at this point are a bad valve or head gasket.....Any thoughts?

Are You Using Exhaust Manifold Gaskets ?

The Fel Pro Exhaust Gaskets That Everyone Uses , Will Burn Out Or Leak Overtime , Especially If Your Manifolds Are Warped

I Finally Had Both Of My Original Exhaust Manifolds Planed At The Local Machine Shop

RemFlex Makes A Nice Manifold Gasket

Why Not Fix The Exhaust Leak First By Pulling The Manifold , Then Go From There

Also It Could Bee Leaking From Where The Header Pipe Attaches To The Exhaust Manifold

Back side of the heat riser bushing bad? (or is that on the driver side? Old memory sucks. Gene

Sometimes the heat riser will cause that sound.

Gasket or no gasket ? Check the manifold with a strait edge !

Use a length of heater (garden) hose like a stethoscope to pin point the leak. One end around the noise, the clean end to your ear.

Dribble a small amount of atf down the carb with the engine at a fast idle. Watch for smoke from where the leak is.

My experience has been the forward most stud will brake.
Seen a lot of this.
The bolt stays in place due to it's long association with the connecting parts, makes it hard to notice.

Your memory is fine Gene, the heat riser is on the drivers side and can also cause these symptoms.

Also the choke stove can leak.

I'd disable the ign & crank it & see if you an pin it down with the stethoscope or heater hose. You might spray some dish soap/water in there & see what bubbles up & I'd try it with no ign then if no results start it & see if you see anything & I'd do it cold so the heat doesn't vaporize the liquid & make diagnosing this more difficult. they say exhaust leaks and some types of valvetrain noises sound incredibly similar. Holler how it turns out.

I bought a CO test meter on Ebay. Great buy. I use it as a sniffer. It is very sensitive. I used it to find leaks in exhaust.
It even help me diagnose a bad head gasket in a 440 once. I had it sniff CO in the radiator. Caught it while the chemical tester was inconclusive.

The meter I bought was a used construction grade level CO tester.
You just have to be careful that it does not get a whiff of the tailpipe. It is very sensitive.

Good reminder as I have one of those CO meters & I am gonna dig it out to confirm my head gasket issue is resolved (& I will keep it away from the tailpipe(s).

If you're hearing a hissing sound while cranking it over I'd say you've got a blown head gasket. The exhaust system will not build up enough pressure by just cranking it over for it to be an exhaust system leak.

Just had this problem. It was a warped exhaust manifold. Check that first with a straight edge. Use the heater hose trick. It works like a stethoscope. Next I would try a leak down test. That will find a blown head gasket.