I have a 1981 Ford F-100 with a I-6 , I recently hollowed out the cat. and put a 3 chamber flowmaster on. I now hear a backfire from time to time not alot , just once in awhile , is that bad ? .

Second question is directed towards the 1st , does a engine need back pressure ? When i was running a straight pipe back for a couple of days i did'nt hear any backfiring, maybe casue it was too loud

thanks.!

 

>I have a 1981 Ford F-100 with a I-6 , I recently hollowed
>out the cat. and put a 3 chamber flowmaster on. I now hear a
>backfire from time to time not alot , just once in awhile ,
>is that bad ? .

Do you mean a loud "BANG" or just a popping sound. I opened up my stock muffler and get a lot of popping on deceleration in gear, but not any louder than it sounds when accelerating hard. This, I understand, is caused by excess unburnt fuel (since there is a closed throttle on decelleration) igniting in the exhaust system. If you get a loud bang it must be a buildup. I would be interested in the circumstances so I can try to duplicate it next time there is a Ch**Y driver next to me that I want to wake up.

>Second question is directed towards the 1st , does a engine
>need back pressure ? When i was running a straight pipe back
>for a couple of days i did'nt hear any backfiring, maybe
>casue it was too loud

As a Ford engineer told me, "backpressure never helps." However, that said, the auto mnfr has to make cars quiet for the general public. The easiest and cheapest way seems to be to induce backpressure and hence, they tend to design the engine, both mechanical and computer parameters to function best with some backpressure. So a lot of back pressure reduction can be done, but at some point you may have to adjust the motor and probably if you want stub headers, you will find a loss of power until maybe the cam is changed or something else major like that. I would think a reasonable sized pipe (say 2.5") out the tail with no cat or muffler should not reduce backpressure too much. Butnot sure.

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i want to do tha mod tall paul did on his truck. where do i punch the holes and how many? do i use a hole punch and hammer or a drill? also is it realy louder?

 

Check it out. I put a photo on this thread:
https://www.ford-trucks.com/dcforum/exhaust/403.html

I have since widened all ten holes to 1/2-inch. It is loud enough that I can hear it on the freeway. It is loud enough that my wife has complained about the noise when I first start it up in the am. I would open them up to 5/8-inch, but for that. I used a high speed drill and aluminum roof flashing with a couple hose clamps around the muffler. There is a slot cut for the muffler hanger and one pop rivet in the end. I suspect that the bigger the holes the louder it gets. Maybe you should get a 3/4-inch drill and try a couple holes right behind the area where the front pipe comes in. Get a long bit so you can add holes without removing the shroud. Keep adding holes until it is loud enough. I think the aluminum shroud is the key to a crisp sound. Now it ain't a flowmaster. It's more of a truck sound to me, but I really like it.

 

u put tha holes on the back of the muffler, right? ill try a few 5/8" holes and try to make a tip. does it need the redneck tip though? cant wait to try it , thanx talpaul for saving me $$$, that is until i sell it, if i do.

 

Yeah, the holes are in the back plate. I found it had a beater sound, kinda garbled with just the holes. The tip is a piece of cake to assemble though. I thought it was a lot of fun because it was one of the few things I could do to the truck cheap and on my own. I'll tell you another mod that is really worth the bucks ($139) is a front stabilizer bar. This truck really corners nice now. I can howl the tires with no perceptible body roll.