The Stovebolt Site Forums The Shop Area Engine Shop Loud exhaust

I recently put on a replacement updraft manifold on my 261. I had it milled and it seems to fit real well with no more hesitation on throttle. When I took it on the road however, it seems extra loud now. I figured the opposite would happen with the leak gone. The muffler isn't that old, so I'm wondering if anyone knows something obvious that I might be missing. Thanks in advance.

I would recheck your work. It sounds like you have an exhaust leak somewhere. Did you use the alignment sleeves?

Yes, used sleeves. Everything looks tight.

I did have the heat riser removed and holes sealed. Would less restriction make it louder?

Usually. By louder exhaust do you mean out the back or exhaust leak loud?

My recent drive this morning I think I do hear a vacuum
leak.

**@#$!!&$@! I apologize, I just had to get that off my chest.

I wondered if I'm running too lean.

It's real hard to give advice with limited info about the problem.

Mike B

Sometimes a new gasket will shrink after it gets hot.
My experience on a downdraft:

Installed new gaskets
Torqued to specs
Ran engine till hot
Exhaust leak...expletive!
Let it cool down a little (too hot for fingers)
Rechecked torque..."loosey goosey"
Retorqued
No leaks

Will the thick Remflex gasket fit an updraft manifold? I think it should, since the head ports are the same regardless of the type of intake that's used. Was there a good reason for eliminating the heat riser? I've been known to duplicate the heat riser shaft and flap valve in stainless steel, and put threaded-in bronze bushings in the manifold on some engines.
Jerry

I had a Reflex gasket on my last manifold and it worked well, however the leak was at the heat riser. I had another manifold which had the heat riser removed, and I had it sperated and milled. It sounds very good at idle and when I give it throttle. I sprayed water around gaskets with no difference. It's when I hit the road around10 mph under load that it makes a chug chug chug noise.

Have you checked the gasket between the intake and exhaust manifolds?

I did install a new one after I thought that was the problem intitialy. A graphite type gasket to help with the suspected leak in that area.

After working on my van today I'm leaning towards exhaust leak. Downgraded engine performance, vibrations, and louder drivetrain emission.

Phak1, I was thinking of exhaust gasket sorry. After I had the mating surfaces milled, one gasket was not enough to level the pipes. I had to use a metal cutout sandwiched between two gaskets.

Anyone have a NOS updraft manifold? 🤣

Chaz 58 Watch it now...your getting into propane territory like I do,take out heat riser weld holes shut with stainless. I suspect that updraft system would work good on propane don't need that sorry choke to wash your cylinders with gasoline every morning. They tell you not to mount propane carbs upside down,never saw a reason you couldn't if it leaks will run over either way. They hated that stub-nose fuel system in under there.

I rechecked the manifold gaskets and one was off a little. A slight realignment and I sealed the leak. Feel blessed. Thanks for the assistance.