People at the drag strip have known it before those engine master guys were even a glint in their daddy's eyes. lol
exhaust pipe diameter for a mildly modified 340
- Thread starter ir3333
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furyus2
Well-Known Member
Maybe so, but due to some of the comments here, not everyone knows.
I agree. The back pressure myth is so strong, you just cannot preach it outta some folks.
VOETOM
Well-Known Member
Back pressure = power loss in most anything we tested. The higher it was, the more power we lost. When none was there, the engine made the most power and the cars ran the quickest, almost 100% of the time.
My 320 HP 340 knew it had restriction but realistically, it only hurt about a tenth and 1 MPH when running 104mph and shifting at 6100.
My 320 HP 340 knew it had restriction but realistically, it only hurt about a tenth and 1 MPH when running 104mph and shifting at 6100.
ir3333
Well-Known Member
Long day....just got in and see lots of chatter. Great stuff guys!
OK... the mufflers are the restriction and back pressure has no effect!
I have watched most of the Engine Masters videos but they are usually for hi hp builds through open headers for the quarter mile.t
I do like a quiet exhaust, Rumble. Ultradyne tech spec'd the cam and said headers would produce no real gain in my build. Engine was built to give good street performance and will never see high rpm.
So...how much gain or loss could you notice driving on the street from 800 to 5000 rpm. 15 hp...20 hp?
OK... the mufflers are the restriction and back pressure has no effect!
I have watched most of the Engine Masters videos but they are usually for hi hp builds through open headers for the quarter mile.t
I do like a quiet exhaust, Rumble. Ultradyne tech spec'd the cam and said headers would produce no real gain in my build. Engine was built to give good street performance and will never see high rpm.
So...how much gain or loss could you notice driving on the street from 800 to 5000 rpm. 15 hp...20 hp?
Back pressure loses power. I'd say that's an "effect".
ir3333
Well-Known Member
Good point!
A 600 hp is pushing out about twice the air as your 340 and has only a 13-20 hp difference between 2.5 vs 3. They said 3” was about par with open headers.
So how much you lose by going 2” ? Instead of 2.5” probably about the same. Unless you put some power killer mufflers on some are terrible and might kill twice that. Testing is the only way to know for sure, I wouldn’t go with 2” but it don’t seem like you overly care about power.
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In my mind....and I know that's gettin dangerous, the biggest need to do away with back pressure has to do with not contaminating the next intake charge with exhaust gasses. Which of course leads to a power loss. I think we can all agree that's a bad thing.
junkyardhero
Well-Known Member
lotta people trying to pick pepper out of fly **** here.
600hp motor loses a few hp/tq, @VOETOM shows 1/10th & 1mph
if you're going from a single or a real crappy dual set up, then sure stepping it up to 2~2.5 with some good mufflers is going to be a marked improvement. but the difference between a 2" system and 2.5" system in a sub 400hp street car? what's the ROI on that? a nickel?
600hp motor loses a few hp/tq, @VOETOM shows 1/10th & 1mph
if you're going from a single or a real crappy dual set up, then sure stepping it up to 2~2.5 with some good mufflers is going to be a marked improvement. but the difference between a 2" system and 2.5" system in a sub 400hp street car? what's the ROI on that? a nickel?
ir3333
Well-Known Member
Correct, i've built a few cars and maximum power or racing is not important, but when i step on it
something has to happen.
I actually bought a complete inexpensive used 2" exhaust just to get me driving when i reach that
point with the current project.
So i thought i would see what some of the more knowledgeable guys on the site thought about how
much would be left on the table? Maybe it will be adequate
something has to happen.
I actually bought a complete inexpensive used 2" exhaust just to get me driving when i reach that
point with the current project.
So i thought i would see what some of the more knowledgeable guys on the site thought about how
much would be left on the table? Maybe it will be adequate
When the time comes Run it and measure the back pressure if it's low then probably good enough if high then a possible upgrade in the future, if you do measure please share the results, also could do open vs the 2" see what difference it makes.
Testing/measuring is the best way.
VOETOM
Well-Known Member
My 340 runs stock manifolds and it likes good exhaust systems.The difference between the very best system and stock setups on mine might be .15 and 1.5 mph so it is not much to worry about unless you need very tenth.
What does matter is the driver's side exhaust pipe out of the manifold. There is some serious power loss and for sure, I'd fix it. Tom Swope at Accurate can bend you 2,5. pipe to get aorund the starter and torsion bar and that is worth doing. The stock set up is about a 2" pipe squashed in half. It has to hurt although I can't say how much since mine has always had a homemade big pipe on the drivers side.
What does matter is the driver's side exhaust pipe out of the manifold. There is some serious power loss and for sure, I'd fix it. Tom Swope at Accurate can bend you 2,5. pipe to get aorund the starter and torsion bar and that is worth doing. The stock set up is about a 2" pipe squashed in half. It has to hurt although I can't say how much since mine has always had a homemade big pipe on the drivers side.
furyus2
Well-Known Member
I went with manifolds, and a TTI 2.5 inch exhaust. The fit on the driver's side is tight, but doesn't hit. I did need to cut a 5/8 wrench to tighten the bolts.
The other concern is sound. Smaller pipes IMO sound like pea shooters.
The other concern is sound. Smaller pipes IMO sound like pea shooters.
VOETOM
Well-Known Member
VOETOM
Well-Known Member
273, this chart above was from testing on Dad's car long ag. Pretty easy to see. We made a single system so we could really see what mufflers did or didn't do.
ir3333
Well-Known Member
Yup, when the time comes i'll install them.The complete exhaust came off a 340 Dart with the same
...549, and ...553 manifolds that i will use. The previous owner/friend restored a show quality numbers
matching 69 340 4speed convertible. I think there may only have been about 50 of those cars made and
these replacement pipes had no business on that car but it won't matter on mine.
...549, and ...553 manifolds that i will use. The previous owner/friend restored a show quality numbers
matching 69 340 4speed convertible. I think there may only have been about 50 of those cars made and
these replacement pipes had no business on that car but it won't matter on mine.
Swinger 340
Well-Known Member
It's not just the diameter of the pipe but the bends also, as well as the type of muffler. I use 2.5 with Walker Turbo mufflers, tail pipes comes out in front of the rear tires (none over axle). This is my van set up with a 70' 340. Note: Being a van, the collector is 2.5". I welded flange to the pipe, then attached to collector, by bolts. I noticed a huge difference between 2" and 2.5".
I wonder if anyone has done a study on decibels of loudness between the different size exhaust using the same mufflers for the given size so you could get apples to apples comparison. That could also be a deciding factor for some of us older folks that don't like too much noise anymore but still like power.
I think the bigger pipes are more mellow sounding. Think of a old pick up with skinny 2" tail pipes cackling up and down with rpm. What a stupid sound!
Stupid!? no way... This is the exhaust i want...I think the bigger pipes are more mellow sounding. Think of a old pick up with skinny 2" tail pipes cackling up and down with rpm. What a stupid sound!
That doesn't sound like a old pickup though. I remember watching those videos. That's like a Commando single exhaust. But if I remember right, that's not the "Hemi style muffler" and no resonator. Sounds great and he really get's after it at about 28 min. Downshift and go. And then at 30 min.
I believe it's actually a resonator and no muffler.. i'm too lazy to go look though
ALso a 340 under the hood now.
Ya. one or the other.I believe it's actually a resonator and no muffler.. i'm too lazy to go look though
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