Settin mufflers under the cab good or bad?

[old_1966_GMC]

So im havein some problems with my dad in where i should put my mufflers so first off i had thougth of puting my mufflers under the cab sence the frame is straigth and make 2 holes in the rear crossmember where the 2 drive shafts connect and have the exhaust tips comin out in front of the rear wheels but this where im have trouble my dad says its not good to put the mufflers under the cab on the frame because if theres a leak it not good to breath the fumes.so what u guys think will there be any problems installing my mufflers under the cab or should i take my dad advise in finding a diffirent place to put my muffflers i mean i really like the way i had n mind but i dont know what to do now PLZ any help or photo would be helpful
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[markeb01]

I have mine mounted vertically under the bed in front of the rear axle, specifically because I didn't want them under the cab. This wasn't because of potential exhaust fume leakage, it was to minimize any possible exhaust droning. My truck has a noisy gear drive and loud mufflers, but there is no droning in the cab at all.

[Rannos]

When running your exhaust you want your mufflers placed as close to the end of the exhaust as possible. There are a few reasons for this. One being the drone in your cab. More importantly IMO is performance. The farther back your muffler is the better exhaust gas scavenging you get and the more potential for power you have. Running full length exhaust on our trucks can be a pain with the cross member and trailing arms getting in the way but what I have seen done is either cut out the cross member like you were talking about or run the exhaust out side of the frame. Running it outside of the frame can cause problems if your have dropped the truck more then a few inches as it crosses under the frame before the trailing arm cross member. Hope this helps.

[lakeroadster]

The "drone" noise that is referred to in the previous posts is caused by the exhaust exiting under the vehicle and the harmonics related thereto, not where the physical location of the muffler is.

Your exhaust "system" needs to be based on the requirements of the engine. For a stock or mild performance build there really is nothing wrong with placing the mufflers under the cab. The only reason they may need to be positioned further back is if you will be using an "H" or "X" pipe which is placed between the engine and the muffler. X / H pipes are not a necessity on a stock or near stock motor though.

Here is an excellent Super Chevy article: Exhaust Science Demystified

My 350 is a mild performance motor. I run long tube headers into Cherry Bomb mufflers under the cab, through full length tailpipes that exit at the rear of the truck. Here are some photos and a video clip.

Good luck to ya and I hope this information helps.

John

YouTube - Lakeroadster's 1965 Chevrolet...

[Rannos]

I agree 100% that the exhaust needs to meet the requirements of the motor and that there is nothing wrong with mufflers under the cab. My mufflers are under my cab as well but my exhaust dumps less then an inche after the cab. The fact still remains the closer to the end of the exhaust you place your muffler the more efficient the engine will run no matter the build. Plus the more pipe you have after the muffler the more of that raspy draw back you get. Some people love that sound and to each their own, but to me it takes away from what could be a nice sounding truck/car. I will link a video of my truck running with the mufflers just before the dumps.

BTW John that is a sweet truck and the way you ran the exhaust is very clean.... mine will be very similar to that when I re-run it, just with the mufflers located just after the axle.

YouTube - 1964 Chevrolet Truck Rat rod.

[old_1966_GMC]

Well my main reason for putting my mufflers under the cab is that the mufflers are 10 1/2 Inces wide and 22 inches in length and these are flo pro performance muffler i picked up at the junkyard sence they still looked fairly new they do sound real good to me sence im running the stock 305 v6 but also i tend to have enough clearance between the drive shaft and frame if u guys have a better i idea then mine tell me and everyone about or post some photos
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[blackedoutharley]

Here is my experience.

On my '65 LBW I had the mufflers mounted under the cab and the exhaust exiting in front of the rear tires. You couldn't hear yourself think inside the cab!

When I had the exhaust replaced I moved the mufflers to just in front of the rearend and installed full tailpipes exiting under the rear bumper. Now I can talk to passengers, listen to my stereo and think.

Full length Hooker headers (2.5" collectors), 2.5" pipe into Flo Pro mufflers. Unless you're running a blower on nitro you will benefit from some backpressure.