hey i just got headers on the car and it has flowmaster 80 series exhaust. this is the situation:
for example if the OEM manifolds are more restrictive than the cat convertors and the flow is opening up at the cats, this should be okay for stock performance. but if the cat convertors are more restrictive than the headers, this will damage performance yes?
also it is sounding a little funny, when i am accelerating or going uphilll. i dont know how to exlpain ut but it doesnt sound bad, just not normal.
BOTTOM LINE: is the solution to get high flow cat convertors? or..
thanks.

 

I have a high flow cat on mine right now. I like it and it allows me to pass smog with it. I would go for it.

 

If you still have the original cat on the car after 15+ years, most definitely change it. I'm surprised you still pass smog with it. By the way, all aftermarket cats are "high-flow." Its all they make now.

Where in Cali are you? North or South?

 

kevin is right.
just had a meeting with the engineers from catco converters. they told us a high flow cat is the same as any other cat with a polished shell.

 

sweet!!! thanks for that! i was lookin at advertised hi flow ones and they seem higher than just the stock replacement.
im in the bay area btw, kinda right in the middle.... north id say cuz i gots da norcal star sticka on me car!! ahaha

 

hey i was wondering what the symptoms are for a header gasket leak because if i am in one of the upper gears (3rd-5th gear) and just coasting (at 2000-2500 rpm), and hit the go fast pedal, the whole car shakes noticeably but not violently, accompanied by what sounds like the sound of detonation until it gets past like 3500-4000 rpm, then its fine.
any ideas?
clutch prob perhaps?
stumped...

 

A header gasket leak will sound like "tick-tick-tick" at idle, and a faster tick when you accelerate.
Your description of the problem sounds like knocking or detonation. What brand and grade of gasoline are you using? Does it still do it if you use a different brand?

 

GUTTEM OR CUTTEM!!!

 

i would but im in **** california. and i am going to put a new knock sensor in a day or two. i am pretty sure it is still the one that was on the 5.0L engine, but its a 5.7 now. that might fix the knock and the timing i hope....
i just used shell, 91 octane, i suppose i could have pressed the 87 button by mistake, but at idle the cat convertors are making pretty loud (for lack of better words) convertor noise. o well ill replace the knock sensor and check back... we'll see.

 

The knock sensor would be a problem only if you are getting a code 43. Some people say the knock sensors are different for a 305 or 350 but I havent noticed a difference in my research.
Is this a brand new thing or something that has gotten worse over time?