I have a 98 F150 4.6 injected. While fixing the exhaust leak in my driver side manifold I could see that my muffler was cracked quite badly. So I decided to just straight pipe the exhaust instead of buying a new muffler. Some of my friends said it could damage my motor without the back pressure. Is this true? Or are they just jealous of the sound?

 

They are jealous of the sound, Magnaflow sells straight pipe muffler and they wouldn't sell something that would harm

 

Straight piping won't hurt it. Enjoy.

 

The only issue you could possibly run into is your your exhaust valves warping...

If your valves cool too quickly because cold air rushes into the open pipe....then valves with small tolerances can warp...causing valve noise...or in extreme cases valves that dont seal...

this is usually an issue in smaller motors (motorcycles and the like) with short tailpipes....but if you have a header pipe that is 8 feet to the tailpipe...it shoudnt be an issue...

 

you will fail your smog check next time with straight piping....

the smog check guy will notice if you remove the Catalytic coverter and will fail you...they do that here in California....

keep that in mind...

 

straight pipes are great,i've ran them on every car i've owned at one time or the other.but today you have emissions to worry about,but if you have cats on the exhaust system.i had a 76 t/a 455 i converted to alcohol removed the cat and passed emmisions but the failed on the safety for not having cats so i went to the junk yard bought 2 cats took them home and knocked the guts out of them filled the cat with quickdry cement with a pipe through the cat had them welded to the header collecter and passed safety.

 

I assume the purpose of the quick dry cement was so they didn't sound hollow if someone tapped on them...?

 

yes they have a thing about modified cars,with the cement it gives a solid sound when they hit the cat with a night stick.it sound hollow they take you car.your jailed and fined.that was the way in the 80s in va.

 

I changed over to liquor uprooted the feline and passed emmisions yet the fizzled on the wellbeing for not having felines so i headed off to the garbage yard purchased rwo felines took them home and knocked the guts out of them filled the feline with quickdry bond with a funnel through the feline had them welded to the header collecter and passed wellbeing.

 

just leave the cats and you'll be fine. the cats will provide enough back pressure and stop any valve problems plus give some noise reduction.