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proper diesel muffler for noise and power


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When I first bought my 67 SII 109 2.25 diesel it had a flex pipe ran out back with no muffler. After driving it for a few days I couldn't stand the loud drone and took off the flex pipe and installed a new muffler I happened to have onto the exhaust pipe.The exhaust exit's just ahead of the rear wheelwell opposite the drivers side.Not only did it not silence the truck very well but, it seems to have reduced my power by quite a bit.

My question is, should I run a pipe all the way out back with the muffler near the back to help with the drone and noise? And, do I need to use a diesel specific muffler to get more flow? Thanks in advance for your help. This great forum has helped with several questions. Mark.

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Exhaust tuning relies on two things:

-gas flow

-exhaust pressure wave

Flow is the easiest to deal with. With diesel you basically want as much flow as possible, there's no need to balance it with back pressure to preserve the tune as you would with a petrol engine.

There are plenty of decent mufflers that flow more than enough not to affect the HP but should still reduce db levels. You may need to look at buying multiple mufflers though.

On a 2.25 you don't really need to worry that much, it doesn't produce much HP. I'd just slap some long sensible sized bullet mufflers in there. One about half way along and one at the back. I'd also run the exhaust all the way to the back of the vehicle as it should drone less and is further away from the drivers seat.

Have a look at Magnaflow mufflers, they are good quality and affordable. Check prices out on Ebay.

I'd say you'd want to run 2" tubing or maybe 2.5" if you want it to look beefier. The bigger the muffler the more silencing affect it should have.

I wouldn't worry about tuning for the exhaust pressure wave - I have no idea how to do it anyhow..

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