I have a 1989 f250 straight cab with the 7.3 non turbo diesel. I was wondering if anyone here has put on a set of dual exhaust stacks in the front of the bed. I have 5 inch stacks from a 378 Peterbilt because they were free. Any suggestions on this install would be appreciated.

 

I don't really like the sound of these diesels when you divide the exhaust, they remind me of what a giant VW bug would sound like. But, with 5" stacks you'd sound like one of the big boys for sure! You might have fun trying to find room for pipes that big, but if your bed is wide enough I guess that might not be a problem. My Dad has a single 4" stack on his 6.9 flatbed and it sounds really good. It got a lot quieter when he turbo'd it though.

 

If I put on the stacks I will probably put on a 3inch muffler from a 02 Dodge Cummins so I dont get a ticket and have that crap cackle sound.

 

Run a single pipe from the down pipes back to the rear of the cab. Then make a flat Y to split it to each stack. Works good, sounds great. I used a three inch flow through muffler on mine. Pics in my gallery, none of the bottom of the truck yet though. I have been meaning to take some of the flat Y that I made to split the exhaust. All it is is a pair of 90 degree ells that I cut and welded together to make the Y.

 

I would try dual 2.5" pipes and thrush magnums, I have heard a few diesels around here that way and there was no snap or anything. The 5" stacks will really enhance the lows too. Best sounding Diesels with galsspacks (I'm sure someone will disagree) the chev 6.2 with dual 2.25" and thrush magnums.

 

do I put the single muffler right before the y? did you bring the pipes up between the frame rails and then out once in the bed to make a wider space between the stacks?

 

I ran mine back from the Y into the muffler and up through the frame to the Y which has the top pipes laying flat pointed to the bed sides. I have an flatbed dump that left me enough room to take the pipe over the frame to each stack.

Hard to explain but I used two 90 degree ell bends laid back to back.
Then I cut enough off the back of each ell to make a three inch inlet pipe that goes into a 45 bend then another 45 bend to get it into the muffler.
The outlets go over the frame and ell up to the stacks.

The piece I made was hinda like a T but by using the ells it has a better flow path for the exhaust.

Also I have each pipe from the manifold dumping into the three inch pipe seperatly, not both coming together and then going to three inch pipe.

I did one on a Dodge that we cut one hole in the bed over the exhaust pipe location.
Then we ran one pipe into the bed and made the Y pipe split the exhaust pipe right above the bed floor and set the stacks at the outside edge of the bed box. Word of caution, the pipes do get very hot while driving. The Dodge owner melted his lunch cooler the first day he drove the truck. It slid against the pipes while driving down the road, lunch was hot, but it smelled like burnt plastic. Bed liners are also at risk without some heat shielding.

With a stock pickup box you have to either go under the frame or put the Y inside the bed. Under the frame is down to low in my opinion.

 

Freightliner used to have a square muffler mounted on the frame behind the cab (on a cabover) the exhaust from the engine entered the center and the stack outlets were on the outside edges of the square muffler. I'm not sure what the inside was like for diverting to the outlets. Probably be a pretty easy fab if a guy had access to a few tools and I don' t think it'd look bad especially if it was chromed.

 

I am using two 5 inch stacks from a peterbilt and I wondered if there was an easy way to hook the 3 inch pipe to the stacks with not much more than a mig welder.

 

I would just get a shop to make the adapters.

 

Money is tight and I can use a millermatic mig to weld what I need so I definitely wont pay a shop.

 

I was thinking of cutting a 5 inch circle out of a piece of 1/4 inch plate steel and cutting a 3 inch hole out of the middle to make the adapter. It would look like a giant washer.

 

You would do much better flow wise to have an angled transition from 3" to 5".
The sudden change will cause swirling that will not flow as well as a smooth surface.

 

thanks for the advice. Im now thinking of buying the pipe and having a shop do the work so I can have it run seperately from each down pipe. I was wondering if anyone knew about how much a shop would charge for this kind of install.

 

Go to a place that sells pipe, they shoud have some reducers there. I got mine from a place here in tulsa, from a pipe supply place. have some 2 1/2" to 4" reducers. They are usually cast iron or steel. Lowes and Home Depot don't wont have 'em. good luck.