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Cat exploded, motor is alive, what next

readymix said:
I will check the distro today. Thanks for the ideas. Keep 'em coming
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My vote is for a muffler bearing coming apart at the header/manifold and clogging up the cat! Make sure they are in good shape and if they need to be replaced buy some that were make in the USA! :haha::haha::haha:
 
The timing was spot on.
So now the question is....will a clogged cat cause the exhaust to run as hot as it did, or do I have another issue?
 
I would think so! Just like on a diesel, if you have a restrictive exhaust you will run higher EGTs. Have you tried driving it yet? If not go drive it up a long steep grade and stop at the top and look at the exhaust. The only other thing I could think of is an exhaust valve not sealing up real well but my vote is for the cat being pluged up.
 
Well both manifolds were red hot so it would have to be more than 1 valve not sealing right.

I can't drive it yet, the passenger side manifold is broken in half. It has been leaking for a while and I guess this finished it off. Time to find that header review thread again:D
 
OUCH! Yeah thats why I didn't think it was a valve. I could be that since your rotor was cracked the timing could have been off before it broke into pieces but now that you have a new rotor on it is running fine. I still think it was the cat but it could have been a combination of the two. Good luck.
 
Maybe the Boom caused the other problems. I have a buddy that drove a 7.3 diesel and I think his waste gate got stuck closed but what ever it was caused enough pressure to go back through the engine that I blew apart his turbo, intake, and filter. Could be the same kind of issue.
 
Reading it now. Few questions about "My Plan"

I will buy the Hedman 69830's.
What size should the rest of the exhaust be. Keep in mind I have a 305 and will upgrade to a healthy, but not obscene 350 in the future.

Y-Pipe ?
2 into 1, to save money.

I was thinking 2.5" would be best, but I am not an exhaust expert.
 
3" to the muffler past the Y pipe is stock on mine. It's 3" all the way out with a Catco cat on it now.
So, to answer the question, 3" past the Y.
 
readymix said:
The timing was spot on.
So now the question is....will a clogged cat cause the exhaust to run as hot as it did, or do I have another issue?
Click to expand...

Its not that your timing was spot on or not. Once your rotor craked and came apart your timing changed. The changed in timing is what most likely caused your glowing CAT.
 
I see. I was not understanding it like that, but it makes sense now that you put it that way.

I will run 3" pipe after the "Y", but what size tube should I build the "Y" out of. From what I have read 2.5" would flow better than the 3".
 
2.25" Appears to be stock for the Y. I just measured it. You don't want the Y to be too big or you will lose a lot of your bottom end, and with a 305, you need all you can get.
EDIT: Use this for the merge. http://store.summitracing.com/partdetail.asp?autofilter=1&part=FLO%2DY250300&N=700+115&autoview=sku
flo-y250300_w.jpg
 
im running dynomax headers, 2.25 true duals, and glass packs on my 305 and Im happy with the power and sound
 
Im willing to bet the cracked rotor changed your timing, That in turn made your engine run rich, your cat will catch the unburnt gas and try to reburn it. Over time this plugs up your cat. the more its plugged the hotter it will get. Fix your other stuff first then maybe smog check it to make sure its not STILL running rich. A cat will plug up fairly fast but it still takes a few weeks, so I would think its been running rich for a while now, maybe a month or more. The backfire was probably caused by the cat exploding and the back fire probably finished off the rotor, hence the 3 pieces.

I would go with 2.5" to the Y 2 7/8" from Y to cat and 3" the rest. This will probably be cheaper and perform the best between the 2 engines.
 
2 7/8" is really close to 3" but its much cheaper by the foot. also a gradual increase in size as you move back has better scavaging than 1 jump or same size all the way back.

My local shop has always carried 2 7/8" pipe, I thought it was common and standard lol. It was the factory size for 6.9 non powerstroke ford diesels by the way, even though ford called it 3"


actually every exhaust I have ever done has been 2 7/8 after the Y or straight from the manifolds. In another thread I said my 77 has dual 3" but its actually 2 7/8 to the mufflers then 3" out with 4"x24" chrome slash cut tips. They have rainbowed like a harleys pipes. It rattles windows at gas stations at an idle, but you hardly hear it until you get on it.
 
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