Cracked headers, any long term issues??

[n55luvr]

I think I've read on here that having cracked headers long term is no real concern. And I'm all for that. My 04 has cracked headers (tick tick tick tick). However after the truck runs for about 5 mins it becomes pretty much totally silent and life is good.

I'm a car guy like most of you and I spend lots of free time reading about mechanical issues of various cars on other forums. Came across something that caught my eye on a Ferrari forum (I know worlds apart in regards to engine architecture and materials but the concept is still the same):

'The headers on the 355 crack, air is sucked into the exhaust, O2 sensor sees excess O2, tells ECU to go rich. Then supposedly this results in raw fuel washing the cylinder wall and, as a result, scoring'


So my question is, has anyone seen anything negative from running cracked headers for any length of time? I have DT headers on my mod list but they are way way down at the bottom. Should they be moved up to the top to prevent any long term issues? My LC runs great, consistently get 15-17 mpg in mixed driving and seems to be reasonably powered.

 

[jcrandall]

fwiw, no issues here. I'm at 270K and the ticking has been around as long as I can remember.
Anecdotal evidence, but better than nothing I guess. I get closer to 12 mpg mixed, but that's probably a reflection of mostly short trips and a bad driving style.

 

[n55luvr]

Exact reply I am looking to find comfort in! I think my previous owner said the ticking had been there for many years and he also never had a concern about it. Never burns oil either. My elevated MPGs probably has a lot to do with my highway commute to work coupled with the 5 speed.

 

[LostAfrican]

Ummmmm......I know its a Ferrari forum and all, but can I just add:
'The headers on the 355 crack, air is sucked into the exhaust, O2 sensor sees excess O2, tells ECU to go rich. Then supposedly this results in raw fuel washing the cylinder wall and, as a result, scoring' - Doesn't make sense to me....first of all, every other cycle puts "raw fuel"/vapor in the cylinder. Also if fuel scores steel/aluminium cylinder walls then its a good thing our cruisers have titanium blocks and glass petrol tanks and we don't ever run the engines rich...

Even if all the above was true....the headers arent going to pull extra O2 in for very long, I understand that the heat makes them expand and seal up again.

 

[hoser]

My guess is the ECM isn't using the 02 sensors to control A/F ratio much during the warm-up phase. If that 'tick' doesn't go away after warm-up, you could have a long term problem.... including failed emissions.

 

[n55luvr]

Agree both of your comments. In theory the hair line cracks typical to our motors seal due to heat expansion. I think with the Ferrari example they may have a much larger crack or hole develop possibly in one of the bends due to high heat and said crack persists at all times, regardless of temps? I also think when a/f ratio tips towards running rich every time you drive you would introduce some problems, scoring of a cylinder wall? Seems odd but who knows.

I have no idea but I don't think this is something I will worry much more about.

 

[Kigiin]

Ticking for over 100,000 miles - still goes away in a few minutes.

 

[Sandroad]

I've got about 50,000 and 5 years on ticking headers when cold and no issues at all. Goes away quickly. On the 02 into the exhaust thing, the headers are under internal pressure from the exhaust gases and if anything it seems exhaust would leak out, not air leak in.

 

[e9999]

also not obvious to me that air would be sucked IN when the exhaust gases are under pressure, that would require a Venturi effect that in turn is dependent on unlikely specific shapes of the tube and crack.

 

[OregonLC]

I've got about 50,000 and 5 years on ticking headers when cold and no issues at all. Goes away quickly. On the 02 into the exhaust thing, the headers are under internal pressure from the exhaust gases and if anything it seems exhaust would leak out, not air leak in.

also not obvious to me that air would be sucked IN when the exhaust gases are under pressure, that would require a Venturi effect that in turn is dependent on unlikely specific shapes of the tube and crack.

I'm a bit over my skis here, but my understanding is that there is a negative pressure wave that exists in the exhaust as the flow stops and starts with valve timing. The overall flow is positive pressure, but there are moments where the pressure is negative. I believe this is a large part of exhaust tuning; getting the negative pulse to time with valve opening to assist with cylinder evacuation.

That said, the annoyance of the tick appears to eclipse the possible collateral mechanical effects in the 100. Further, the stock headers have such short individual runs it probably negates any real scavenging that could be going on.

 

[e9999]

I'm a bit over my skis here, but my understanding is that there is a negative pressure wave that exists in the exhaust as the flow stops and starts with valve timing. The overall flow is positive pressure, but there are moments where the pressure is negative. I believe this is a large part of exhaust tuning; getting the negative pulse to time with valve opening to assist with cylinder evacuation.
snip.

that does sound reasonable but whether air would be sucked in to any significant amount would depend a lot on the position of the crack and shape of the manifold, I would think. So, does not seem like a given to me. But am no exhaust expert by any means.