I had a flowmaster 40 series installed yesterday on my 86 F-150 302 FI along with new pipes(not duals though). I basically just replaced the stock exhaust from the cat back with the same thing with the exception of the new muffler (stock size pipe with single entry & exit flowmaster 40 series muffler).

My problem is that it is VERY quite (honestly) and it "puffs" when I let off the gas (I am assuming it is a back pressure problem). I did not want an obnoxious loud but the deep throaty sound of a 40 series flowmaster. Does anyone now what could be wrong or should I expect a quite sounding system since I did not run true duals? Could it be my CAT's are bad? Would removing the cat's make it sound more like a true 40 series or would it still "puff"?

Basically when it idles you can tell I have a new muffler but when I give it any gas at all, it sounds very quite just like stock! You can't even tell it's an aftermarket muffler????

Please help if you can!!

 

I think it's notmal for it to puff and sputter a little when you let off the gas because of less back pressure, all of my vehicles with performance exhaust do the same thing. And yes, the exhaust will sound louder without the cats.

-Jon

 

Thanks for the help. I am thinking of cutting off one of the older cats and leaving the smaller/newer one on. Maybe this will help it out some? The older cat might be bad anyway.

Thanks

 

I looked under the truck last night and the "puffing" sound is coming from the pre-heater, which is located right before the cat. This looks to be the original pre-heater for the cat, so I'm sure it's got to be bad after almost 17 yrs.... I might go ahead and cut the cat off to, since it will help my performance and sound. I am going to keep it though, just in case it won't pass inspection next July.

Thanks everyone

 

its a pre cat, not pre heater