I have a 1990 F-250 with a 5.8. I installed long tube headers with an O2 sensor bung welded into the right side header. After that I took it to a shop and had them build a true dual exhaust system for the truck, and due to limited finances and a need to get the truck on the road quickly, I opted for a cheaper set of Cherry Bomb Turbo mufflers. When I spoke with the shop, we agreed on 2.5" exhaust as opposed to the 3" I had originally asked for. When I got the truck back, it was only 2" pipe, but I shrugged it off because the truck was running and I needed it to work.

That was about a month and a half ago, and now it seems after driving it for awhile that the rather small Cherry Bomb mufflers along with the small 2" piping is creating too much backpressure. I say this because the mufflers are splitting at the seams and im assuming this is because of a massive amount of backpressure because of the mufflers that are severely undersized.

Basically, Im asking if im right in my suspicions? And when I take it back for bigger mufflers (probably Flowmasters or Magnaflows), should I have new, bigger piping ran too? Ive been researching, and I dont see anybody running such a small setup on a big truck like this. Ive read that Lightnings have 3" exhaust, and seeing as I plan on upgrading the intake manifolds and injectors soon, should I run that big of a pipe?

 

Hate to see something unanswered. Just my opinion, 3" is too big. The 2.5" like you decided sounds right. As far as mufflers splitting, that sounds like a defect. Unless you had a heck of a backfire, can't imagine that happening. Don't know what warranty you got with the system, but they didn't do what you wanted plus you have problems. I'd get back with them. I deal with Interstate Muffler due to the fact it's warrantyed as long as you have the vehicle. Never had to take one back in 45 years.

 

If they crush-bent the pipe then there are areas that are probably 1 1/2" or smaller in diameter. That is too small. 2 1/4" mandrel bent or 2 1/2" crush bent is way better. What ever muffler you choose should have the same core diameter as the tubing.

I had a 73 F250 with the 360FE engine. My first exhaust was headers with 2 1/4" duals and turbo mufflers dumping in front of the rear tires on each side. When those mufflers broke apart I had a reputable shop install new turbos and tailpipes over the axle and out the sides after the tires. First trip I had lost all my added power. After discussing the problem with some friends we decided to cut the tailpipes off and dump under the truck before the axle. All my lost power came back. To this day I won't use crush bent tubes opting for mandrel bent pieces.

 

There really wasnt any warranty with the exhaust, I got it done just for the price of materials really because its the shop I take my truck to for any repair I cant handle. And the mufflers I have are honestly about 1/3 the size of a Flowmaster 50 series. The mufflers were only $20 a peice though, so I could expect too much out of them

 

The one good aspect of it all was that it was all mandrel bent and the welds were almost all leak proof. I paid $60 for the whole setup to be bent and the mufflers to be welded on. I supplied the mufflers.

But I will say, the cheap Cherry Bomb Turbo mufflers arent welded, they are all crimped on the edges, which Im pretty sure leads to the seams blowing out. And the small mufflers lead to constant droning of the exhaust. These tiny little mufflers are constantly being maxed out. I assume so anyways? Its the same concept of how some mufflers are rated for a certain horsepower, and if you have a Flowmaster 40 on a 1500 hp motor, it would choke the motor.

I honestly dont know the science behind it, Im only 19. All I know is from my experience so far. I apologize if I sound like an idiot

 

I agree about the cherry bomb mufflers not holding up well. Blew some apart on my 5.0 Mustang GT and would have been cheaper in the end if I just had spent the extra to buy Flowmasters the first time. I am also curious if they ran a crossover pipe for you. You really do get better performance with crossover on most applications and unless the computer was set up for O2 reading on just one bank I am surprised the truck is not running poor (getting loss of performance and gas mileage) or throwing codes at you.

Had seen on my brothers older Ford Probe that exact issue when he bought a header kit and the O2 bung really only reads one half of the exhaust. The car was running poor and getting terrible fuel mileage until I welded a bung down the pipe further so it was seeing all the cylinders exhaust go by.

 

They didnt put a crossover on it, then again I never really asked for it. I told them I was on a budget so they did what they could. And stock there was only 1 o2 sensor on the passenger side

I plan on taking it back soon and getting a whole new mandrel bent 2.5'' system with an H-pipe and probably Flowmaster super 44's. The exhaust currently dumps in front of the rear axle, and I'll probably end up doing the exact same thing with the new system. I will say though, the mileage is down right horrible. When I say bad, I mean like 5 mpg with my lead foot. I think several things are contributing to the loss of mileage, and I believe with a new exhaust setup, I should gain back the mileage I lost. You would think with a cold air intake, headers, and a full tune up I would gain mileage, but I think my exhaust setup counteracted everything I did.

 

I think I would really look into this to see if that "stock from factory" exhaust was reading from just one side / bank of engine. The computer adjusts based on what it reads from the sensors and if half the exhaust is not being seen it makes the computer think something is wrong so it adjusts to try and fix it. I have seen it kill fuel mileage but maybe yours is OK reading like that but that would be strange to tune on half the engines output. If the truck came with single exhaust and the two stock manifolds met and then the sensor was there it would be reading both.