How did you run your single exhaust?

[MikeOneZeroZeroNiner]

I feel like I'm beating a dead horse here since there are so many exhaust threads on this website, but none of them really address my question.

After a broken U-Joint incident down in San Diego, I am running straight pipes, and it's just too loud. I want to run a 3" exhaust from the manifold back; what crossover or Y-Pipe did you use? I've read the threads that say that the small block gassers will bolt right up to our manifolds, but the biggest diameter I can find for the crossover pipe is 2.5".

Where did you get your 3" Y-pipe/crossover?

Also, where did you run the piping? Is it in the stock hangers? If so, which side?

 

[Barrman]

The manifolds only let you leave them with a 2" OD pipe. Look at your stock pipes. They swell out after leaving the manifolds to 2.25.

I am using a set of M1009 manifolds on a HMMWV can engine in my M715. This week is the start of building the exhaust system. All I had is the manifolds. I took them to a muffler shop and had them make some down pipes and put the flares in for the donut gaskets. 2.00" pipe is all that will fit. We found collars for a small block system to hold the flares to the manifolds.

I was wanting to go bigger myself. But the price of 3" compared to 2" plus how much harder it is to fit the bigger pipe in tight places convinced me to stay 2" all the way back. I found a Cherry Bomb dual 2" in single 3" out muffler that I will probably order. I want to at least look stock with a single pipe out the right rear of the M715 even though it will be a bit bigger than stock.

The diesel page.com books about the 6.2/6.5 have a good bit of discussion about how to get 2.5 pipes from the manifolds out. I personally don't think it will make all that big a difference on a NA truck that won't see high rpm. Sorry I couldn't help you about the cross over stuff, but you might be chasing something not needed or not available.

 

[MikeOneZeroZeroNiner]

I found a shop here in CA that quoted me $350 to fix my stock exhaust and only $375 to run full 3". So I went with the full 3". It looks pretty good, sounds great, and I can feel a very slight increase in torque at low-rpm from a stop. My only concern is that it hangs down a little lower than the stock pipes (which were tucked up pretty nicely.

 

[twomorestrokes]

My only concern is that it hangs down a little lower than the stock pipes (which were tucked up pretty nicely.

That's the main thing that i am trying to avoid as mufflers catch on a lot of things off road. My original plan was to go to a single exhaust with a crossover from an '87 350 truck app and have the muffler in the bed with a pipe and heat shield (like a semi tractor) I really don't know how you could feel any performance gains/ losses on these low performance trucks with exhaust changes.

My latest plan is to turbo the 6.2 which mandates a single small diameter downpipe and a single exhaust. Have you seen the restrictive exhaust dump on a GM4 turbo and downpipe diameter? That's all 8 ports shoved through that tiny single pipe and it's a turbo application.

Bottom line is 2.5" or 3", single or dual, I really don't think you need to worry a great deal about slowing down a N/A 6.2.

 

[67_C-30]

That's the main thing that i am trying to avoid as mufflers catch on a lot of things off road. My original plan was to go to a single exhaust with a crossover from an '87 350 truck app and have the muffler in the bed with a pipe and heat shield (like a semi tractor) I really don't know how you could feel any performance gains/ losses on these low performance trucks with exhaust changes.

My latest plan is to turbo the 6.2 which mandates a single small diameter downpipe and a single exhaust. Have you seen the restrictive exhaust dump on a GM4 turbo and downpipe diameter? That's all 8 ports shoved through that tiny single pipe and it's a turbo application.

Bottom line is 2.5" or 3", single or dual, I really don't think you need to worry a great deal about slowing down a N/A 6.2.

You're going to have to modify the down pipe on a 6.5 setup anyway to fit your truck, but the inside of the turbo exhaust housing is only a little over 2.5", so going a whole lot bigger afer the downpipe on a 6.5 turbo only helps very slightly. In others words, going to a 3" or 4" system using the stock exhaust housing won't help all that much - the turbo itself is the bottleneck.

As far as tucking a 3" pipe, my 3" system is slighter higher that the factory set at the rear of the truck, and actually tucked even tighter under the truck before the axle. I used a welded bullet style 3" muffler that doesn't have an "edge" to hang on like a oval shaped turbo style muffler. There's plenty of room to tuck a 3" system up tight on these trucks. I have more ground clearance for my exhaust now than I did with the stock set-up.

http://www.youtube.com/watch?v=dBEivdlaPL4

Here's the location of stock tailpipes to compare to mine.

http://www.youtube.com/watch?v=htSWxx_Mdks

 

[twomorestrokes]

That's the way I see things C-30. With these tiny outlet stock manifolds or the small outlet on the turbo when going that route, dual 4" pipes are WAY overkill. Looks cool but lots of needless $$$ spent. I'd stick with 3" max. True duals on a stock application is fine, as well as a single 3" system if you want to drop one side of the piping. I plan on a single 3" pipe from the turbo, just not sure yet whether it will be outside the frame rail or inside. I'm fine either way since it will be out of sight either way until it comes up through the bed. If the pipe is outside like a lot of guys do, it would put the stack in the bed corner instead of closer to center if it were inside the rail. I plan on topping it off with a weather flap at the outlet behind the cab.

 

[67_C-30]

That's the way I see things C-30. With these tiny outlet stock manifolds or the small outlet on the turbo when going that route, dual 4" pipes are WAY overkill. Looks cool but lots of needless $$$ spent. I'd stick with 3" max. True duals on a stock application is fine, as well as a single 3" system if you want to drop one side of the piping. I plan on a single 3" pipe from the turbo, just not sure yet whether it will be outside the frame rail or inside. I'm fine either way since it will be out of sight either way until it comes up through the bed. If the pipe is outside like a lot of guys do, it would put the stack in the bed corner instead of closer to center if it were inside the rail. I plan on topping it off with a weather flap at the outlet behind the cab.

IMO, the only way to truly utilize a 4" or bigger system on a 6.5 turbo is to replace the housing of the turbo. I built a custom rear housing out a peice of 4" mandrel bent pipe and made a 1/2" thick flange at work. It required running outside of the frame rail and considerable clearancing of the inner fender, but it really makes a GM-3 turbo spool. It sounds and acts a like a much better turbo, and the EGT is lower than a normal GM-3 turbo.

http://www.youtube.com/watch?v=nXhvZP9wryk

 

[chevyCUCV]

Maybe you should get a bigger turbo?

 

[67_C-30]

Maybe you should get a bigger turbo?

A bigger turbo on an engine that can't handle more than 12 psi is pretty much pointless. The GM-X series turbos work well for what are designed to do, but the hard 90 in the exhaust housing is very restrictive. My exhaust was cheap mod that improved low end spool tremendously. It would't work in some applications because of the size, but I had room in for in the dually, so I made it.

I am eventually going to retofit a GM-X turbo with a smaller, straight rear housing to replace the Banks turbo on my M1009. The quick spool ability of a free flowing GM-X would be way better than this non-wastegated turbo onthe Banks. With 3.08's and 33" tires in the M1009, the Banks lags significantly at times. I love the Banks manifolds, but I prefer the GM-X 6.5 turbos.

 

[twomorestrokes]

Maybe you can answer my question 67_C-30. My turbo setup came with everything except the factory oil feed line. When making my own, do I need some type of restricting orifice in there or is it just free flowing pressurized oil? Thanks.

*edit: oops, wrong thread. didn't mean to jack the exhaust thread.