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4 Inch Exhaust?

OD_Coyote

Active member
887
58
28
Location
North Bend, WA
The “j” pipe on my M35A2 will need to be replaced in the near future and I was thinking about going to 4” diameter pipe instead of 3.5”. Has anyone gone down this road before or have any thoughts/observations to share? I am hoping that the larger exhaust may help lower the EGTs a little and perhaps make the truck sound even better. I was wondering what I could do to improve the air intake system as well?
 
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LanceRobson

Well-known member
1,638
206
63
Location
Pinnacle, Stokes County, NC
The size of the multi-fuel exhaust was purposely kept a little small to accelerate the exhaust fumes up and away from the troop compartment (the bed). The Army knew from the start that the truck would breath easier with the bigger pipe but saw it as a troop safety issue.

I'd say "change it" and post the results, please!

Thanks

Lance

EDIT: Anybody know where to find a couple of 5-ton air cleaners? That mod has been on my mind for a while.
 
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Hammer

Well-known member
1,483
398
83
Location
Winlock, WA
I put 4" exhaust and muffler on mine starting at the fender. It still has the stock bottom 3.5" section, then it necks up at the hole in the fender.
Sounds good, and runs well, but I didn't have a before/after comparison for EGTs.
Just make sure to keep the bends nice and smooth when making it with 4", and it should work well.
Worst case is you spent some money on a bigger exhaust that sounds a little different from stock.
 

OD_Coyote

Active member
887
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Location
North Bend, WA
Thanks for the feedback folks. I will post updates on this project as it progresses. Does anyone know where I can get a 5 ton air intake/filter assy?

Thanks.
 

bgekky3

New member
243
2
0
Location
Huron, Ohio
My dad's shop is next to a chrome shop. They are always throwing away 6" stacks. Once I get there (next week) and get settled, I am going to run a duel 6" straight pipe set up. I will post the before and after data. Right now I think I am overfueling, but I am going to get that straightened out this week. I am at 1100 unloaded accelerating so I think the fuel was turned up on the new engine. On hills the pyro climbs faster than the tach.
 

SasquatchSanta

New member
1,177
18
0
Location
Northern Minnesota
I installed a vacuum gauge under the steering column in place of the air breather warning devise on my deuce. Even with the LDS-1A engine the stock deuce aid breather pulls very little vacuum. The exact numbers are posted somewhere on the site but I can't recall what they are at this time. I would say as long as you keep the stock deuce air cleaner clean you're not going to gain anything by installing a 5-ton unit.

As someone that has gone the route of turning down the fuel I would say not to neglect the droop screw. My LDS engine was seriously over fueled from the rebuild depot. I turned down the main fuel setting two flats and the droop screw 1/4 turn. It didn't stop smoking until I turned down the droop screw.

I made several posts on this subject. In one I even did an on-road manifold pressure test. If you scan my previous posts you may find some insight.

I think you're on the right track in increasing the exhaust pipe size.

Good Luck.
 

Larry Weibert

Active member
102
119
43
Location
Youngstown New York
I have been reading the deuce exhaust treads for some time. I plan on doing monthly camping 2.5 hrs from my home for local Rocket launches. Its probubly 3.5 hr in a deuce. I am thinking of going out the back of the deuce with the exhaust and using the exhaust stack placement for the intake. Any thoughts on that.
 

Hammer

Well-known member
1,483
398
83
Location
Winlock, WA
Exhaust out the back makes a BIG difference!
The motor is a high compression motor, so it makes it's own noises. But moving the exhaust down and back makes the biggest difference you could for these trucks.
 

77 AMG

Active member
403
62
28
Location
Owingsville, KY
Exhaust out the back makes a BIG difference!
The motor is a high compression motor, so it makes it's own noises. But moving the exhaust down and back makes the biggest difference you could for these trucks.
@Hammer. Would care to explain how this would work better for the engine, as opposed to the stack style exhaust? Both of my Semis' were "stack" trucks, so, I am not seeing how this would be a benefit? Thanks
 
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