Blown Header gasket back pressure ?

[Pops Fun]

Hi
Just changed my engine combo making 623rwhp , put my cats on to quiet down the roar...
Must be getting old. Then blew the exhaust gasket , wondering :

Could the exhaust changes, (Cats) put more pressure on the header gasket and blow it??
.
.

 

[Noobz347]

More likely, you have a header flange that's not completely flat or bolts that are backing themselves out.

 

[Gearbanger 101]

I see you're running Mac's....blowing out a header gasket isn't uncommon and it has nothing to do with you running cats.



The individual flange design they use is a poor one. The pipes flex and move around with the various heat cycles and once the headers have been removed, they almost never line up and seal the same. My advice to you would be to spend some money on some good gaskets (not the cheap crappy paper ones Mac gives you with the pipes) and add a liberal coating of high temperature copper silicone to both the header flange and the header gaskets before bolting them back on. Then, tighten them uniformly from the center outward, torquing them on in stages.



That's what I had to do to finally seal up my last set of Mac's. They're not a horrible header, but they aren't exactly maintenance free either.

 

[ProKiller]

i despised my mac's for this very reason. always had header gasket failures.

 

[Pops Fun]

JBA Ford Shorty Headers

They have nice thick flange??

http://products.jbaheaders.com/detail_shortyV.asp?id=1624S-4JS

 

[revhead347]

I wouldn't say it's the cause, but running cats on an engine making that kind of power isn't really a good idea anyway. They definately do cause back pressure, but in all reality cars making that kind of power have a tendancy to blow header gaskets.

Kurt

 

[Venom351R]

what torque stage should header bolts be done in? I'm installing my longtubes in a few weeks

 

[Gearbanger 101]

JBA Ford Shorty Headers

They have nice thick flange??

http://products.jbaheaders.com/detail_shortyV.asp?id=1624S-4JS

Sorry, I was under the assumption that you had the Mac headers listed in your Car Domain link?

JBA's are pretty low end IMO. I'm not sure what the OHV headers are like, but the ones for the modular crowd are notorious for cracking.

In my opinion....if you insist on going with a short tube header, the Ford Racing ones will be your best bet for proper fit and finish.

 

[ProKiller]

we're all the bolts torqued down still or did one of them wiggle a little loose? had you retightened them after you heat cycled the engine a couple times? what bolts do you have in there now?

 

[revhead347]

what torque stage should header bolts be done in? I'm installing my longtubes in a few weeks

I don't remember exactly what your headers look like, but I assume they have a single flange. Tighten from the inside out. They don't have to be that tight, just nice and even.

Kurt

 

[Pops Fun]

Sorry, I was under the assumption that you had the Mac headers listed in your Car Domain link?

JBA's are pretty low end IMO. I'm not sure what the OHV headers are like, but the ones for the modular crowd are notorious for cracking.

In my opinion....if you insist on going with a short tube header, the Ford Racing ones will be your best bet for proper fit and finish.

I had the mac's didn't like them... The JBA"S flange looks much stronger. My MAC's were pretty bad!!

 

[Pops Fun]

we're all the bolts torqued down still or did one of them wiggle a little loose? had you retightened them after you heat cycled the engine a couple times? what bolts do you have in there now?

They were still tight, going to work on it next week. Pretty sure we retightened after running the car, it's been a while and with my memory..