you have no cat???

 

Hmmm secure= hangers....means the pipes won't crack...don't ya think?Cast Iron is more rigid than steel especially the pipes....they'd bend then break theoretically.....

JR

 

dont look like it lol. that means none of our trucks do...i took care of that problem on our powerstrokes.

 

Being more rigid is EXACTLY why they do break. Cast iron will break before it bends. The cold rolled steel tubes, however, will bend an enormous amount, and spring right back. That said, they will exert a LOT of force on the manifold when the engine isn't where it's supposed to be. That's a mighty long lever on a very short fulcrum (bolts at #4 and #8). My 5678 mani broke between 6 and 7, AND between 7 and 8 (3 pieces). 1234 mani broke between 2 and 3, and you could see where the manifold slipped under the bolts at #3. Something (the exhaust system) snatched the hell outta the end of the manifold to do that.

I speak from experience, that even just a misfire condition that causes the engine to lurch in the mounts WILL break BOTH manifolds. I've got Ford Racing shorties on now because of that very problem. After a dealership tried 4 times to make my truck run right, all they did was make it worse and tried to hide it by retarding the timing to 6 degrees BTDC. The lurching and snatching broke both manifolds. The mis-fire got so bad, it would jump out of OD going down the interstate. Y-Pipe, plus cats, plus muffler before you get to the first hanger behind the muffler, so that's a LOT of weight in the exhaust system, and a lot of torsion and inertia hanging on the mani's. The steel pipe doesn't get nearly as hot as the cast manis do either. This tends to make the cast iron even more brittle with age. If you've got a 5.0/302, with cast manis on it, expect some breakage with age, because the carbon that keeps the cast iron malleable burns out of the metal, and extreme heat tempers it more. Just the nature of the beast. If you're replacing broken manis with non-Ford parts, again, expect some breakage. The only reason I put shorties on instead of new cast manis was they were about the same price as the cast manifolds from a dealer, installed. A direct bolt-on that gave me a mild performance increase, but nothing to do the hamster dance about.

BTW, ever dump cold water in a red hot cast iron skillet? Wear a kevlar vest and full face shield if you want to try that little experiment. This is something you can get away with using a steel or aluminum pan, but the cast iron is not so forgiving. Now, think about what kind of stresses hit those manifolds when they're hot and cold water splashes on them. A 1 inch deep puddle will throw enough water up in the engine bay to soak everything at 30 mph.

 

Yep the manifolds must be prone to crack. when i got my truck i had to replace them both. the passenger side was so bad that it broke into 4 seperate pieces when i took it off. ine fact i went to the junkyard for a replacement and the ones i found there had cracks in them too. so i bought new ones from ebay.

as for running weak. my 302 is a dog too. very weak. mine still has the cats and i am going to look into them to see if thats my problem. i could see how it would make it run weak if the cats are clogged since its a 2 into 1 exhaust system. has never run hot though. must be pushing out just enough to not make it run hot.

 

PAINT....thank you for proving my poitn to jr...the cast iron is so much more rigid that there is no dexterity in the materials as is not the case with steel piping...he said exhaust pipes will crack....NO they won't.

Brian...i dig the GPW.....

JR

 

if I ever get down florida way I'll bring ya some cracked exhaust pipes-better yet when the weather gets better up here I'll send ya some pictures --not trying to bust your ***** just have 2 broken ones in my yard

 

More than welcome to....

JR

 

I had a 93 5.0 5 speed and when the cats plugged up it began to lose power especially on hills. I was towing a 24 foot pontoon boat over some pretty good hills and was beginning to over heat and lose power -- everything seemed ok until the manifolds cracked -- became very loud and all of a sudden I had my power back and it would climb over the hills like a new truck. Replaced the manifolds and the cat and that seemed to cure it. IN years past I have seen y-pipes be made out of double wall pipe and the inner would collapse and choke the flow down to the vehicle would hardly even run. Check for plugged exhaust beyond the cats too.