Cracked Exhaust Manifold

[Anonymous]

I was curious how a car would run with a cracked exhaust manifold. I'm guessing the car would run rough, loud, and idle bad (umm... like how my car has been running...) I just bolted on a spare one after porting and polishing it. I also had to open up the exhaust outlet a little more so the exhaust pipe would fit better. I guess that explains why it didnt match up quite well on the old manifold. It's hooked into a two inch exhaust pipe... I guess that wasnt standard on a '66? I havent been able to test it yet and probably wont be able to take it out for a drive until later this week so I thought I'd ask.

 

[66Sprint6]

I drove mine around with a crack manifold for a while. Then I got a better one that the exhaust wouldnt stay bolted to so I ran it opened manifold for a while. Not a good idea I was told, but it ran fine. Took the head off and the valves showed their complaints to my driving like that, but it still ran fine. LOUD, but fine.
Matt

 

[scottiedawg66]

it runs fine, but you run the risk of burning your valves. Get it replaced pretty quickly.

 

[ludwig]

An exhaust mainfold with a small crack will often swell up with heat and seal the crack so there is no increase in sound after the initial warm-up. Eventually the metal will work and the crack increase to where it is neccessary to replace the manifold.
At this point, get the tuned headers from AzCoupe on the Shop site and put in the port divider. You'll love the difference.

 

[Anonymous]

I took my car for a short test drive around the block and now its loud from the back instead of the front! I was surprised at how smooth and quiet the car ran and thought I stalled out a couple times. I took a closer look at the old exhaust manifold and it had several cracks and the heat tube between 3 & 4 was corroded out. I guess that's why the previous owners had the holes blocked up for the choke tube.
One day I'll put the headers and port divider in but I'll need to have the bracket extended for the alternator since I have a/c and I need the time and the money... oh well... one thing fixed, a million more to go...

 

[ludwig]

A new "stock" exhaust manifold is available from NPD. I got one from the boneyard for 90.00. It was blistered and burnt between 3 and 4 so I had to tap and plug the heat riser. The new casting was only 20.00 or so more than the junk one.