Headers vs 340 manifolds

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65 Cuda 340 said:
Just to update a bit, I took my 67 Barracuda to the strip a couple of months ago. I went from 13.70s at 98 with stock 340 hi-po manifolds, 2.25 exhaust and 3.23 gears to 13.07 at 106.5 with TTI headers, 2.5 inch exhaust and 3.55 gears. Both times through the mufflers. With a pretty dinky cam (.450/.455 lift).

That's a 3/4 second improvement from headers with a virtually stock 340 (Duster) and a very mild 360 (Barracuda). Not sure why anyone would be skeptical of a half second improvement with headers over exhaust manifolds with a stock or near stock motor.
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Eight and a half mph in the quarter is about 75 horsepower. You did NOT get 75 horsepower from a header swap on your car.
Maybe, if going from logs and a single 1 3/4 exhaust on a hi-perf 440 you could get 75 out of headers and good exhaust.
 
On a dead stock 340, most dyno tests have have seen are better than 30hp. This of course is not only a low end report but just a matter of what parts were tested as such header design, tube size, collector length, exhaust pipe sizing and length are all factors along with what ever muffler you use. Most choose the sound of a muffler over what actually makes HP.

To this end, end build choices and the muffler choice, dependent, on how he mufflers actual ability, you could throw away 15 to 100 hp away.

While no one in their right mind outs a stock muffler on a tunnel ram build, I’ve seen idiot choices that are nearly as bad.

Research!
 
I have seen dyno tests of headers, cutouts, and mufflers, where a completely mismatched garbage system was used as a baseline, in order to make the parts they are promoting/selling look as good as possible. GIGO testing.
(Example: EM trying to make cutouts look good. 800hp bbc, that needs 3 1/2 pipes with straight thru mufflers, gets tested with 2 1/2 exhaust and triple pass turbos of questionable quality. OF COURSE, the cutouts look good! Put the right system on it, the cutouts won't do squat!)
 
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I sometimes wonder how people drive. I have been driving cars with headers for fifty years, and haven't "smashed" a header pipe yet!
(And I have cars that have the oil pan hanging below the headers, and I haven't smashed one of those yet either!)
 
str12-340 said:
I think that this is 100% BS

I would bet that your customers are reacting to sound and such (I'm glad they are happy!).

Then if the car is mainly a street car you have to live with all the issues of a crowded engine compartment, smashed pipes from speed bumps, etc. After years of 5 different brands of header, I scrapped headers on my street cars and went back to well chosen manifolds and a well designed exhaust system. I never looked back...
Click to expand...

Lol, this is so typical of the arguments I have with customers when quoting a build, it's all good till we get to the headers and the customer says he's done with headers, leaks, speed bumps, road hazards, etc. lol

I tell them I dont build a big h/p engines to put in cars with stock exhaust, won't do it,
BUT - - I add, - I WILL put those hi-po ex manifolds on (pointing at a set hanging on the wall) if there's any leaks or speed bump issues with the suspension left alone . There has never been an issue on vehicle stance .

That's over a dozen builds ago, manifolds are still hanging on the wall.
These new design headers by TTI and Dougs are a vast improvement over the **** from decades ago

As to closing the exhaust, we ran "caps" that used the 3 bolts and a plate to close the header, then ran a street exhaust from a tube welded into the inboard side of the collector to the exhaust pipe ahead of the muffler.
Just unbolt the cap, and go racing.

Cheers
 
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I Installed a set of Doug's headers on my 340-.030 over 68 block with 71 J heads with 2.02 intake valves.
I noticed a huge improvement from idle through the entire RPM range, and I am only running a 9/16 ths street cam.

I can tell you that headers were one of the biggest performance improvements I've had made!

I plan on installing a Edelbrock RPM intake to replace my cast iron intake , not sure how much I will get with that change?
Bottom line is headers add power everywhere!!!
Click to expand...
 
Mike 340 said:
I plan on installing a Edelbrock RPM intake to replace my cast iron intake , not sure how much I will get with that change?
Click to expand...
the stock 340 intake is a really good piece you might see minimal gains with the RPM. the RPM air gap or an LD340 might squeeze a few horsepower more out of there though....
 
Inertia said:
As to closing the exhaust, we ran "caps" that used the 3 bolts and a plate to close the header, then ran a street exhaust from a tube welded into the inboard side of the collector to the exhaust pipe ahead of the muffler.
Just unbolt the cap, and go racing.

Cheers
Click to expand...
And nowadays you can buy them premade with a remote control operated valve that activates the cutout, how times have changed eh?
https://www.amazon.ca/Energy-Exhaust-Cutout-Electric-Wireless/dp/B01MXLXT0G/?tag=fabo03-20
 
If you were able to increase a stock 340 by 15hp by adding headers, could you feel the additional 15 hp in a 3600lb. car?
 
ir3333 said:
If you were able to increase a stock 340 by 15hp by adding headers, could you feel the additional 15 hp in a 3600lb. car?
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Why wouldn't especially at lower rpms where the hp gain percentage is higher eg.. 15 hp @ 3000 rpm vs 5000 rpm.
 
ir3333 said:
If you were able to increase a stock 340 by 15hp by adding headers, could you feel the additional 15 hp in a 3600lb. car?
Click to expand...
Or look at it this way hp is 57% of torque at 3000 rpm so 10-15+ hp at 3000 rpm is 18-26+ lbs-ft at 3000 rpm, is 20+ lbs-ft down low worth it ? It's basically like adding 20 cid.
 
rumblefish360 said:
On a dead stock 340, most dyno tests have have seen are better than 30hp. Tno testhis of course is not only a low end report but just a matter of what parts were tested as such header design, tube size, collector length, exhaust pipe sizing and length are all factors along with what ever muffler you use. Most choose the sound of a muffler over what actually makes HP.

To this end, end build choices and the muffler choice, dependent, on how he mufflers actual ability, you could throw away 15 to 100 hp away.

While no one in their right mind outs a stock muffler on a tunnel ram build, I’ve seen idiot choices that are nearly as bad.

Research!
Click to expand...
Ive seen plenty of STOCK 340 dyno test without mufflers it was never more then 20
Stock builds thru manifolds make 340 hp downhill with the wind.
You are not getting 370 hp bolting headers on that top of the line build with a stock cam.
 
Here a manifold & header shootout on a 300 hp 5.9l Magnum crate engine.

https://www.motortrend.com/articles/mopp-0307-installing-exhaust-headers-into-300hp-crate-engine/
Legend318:Stock '69 A-Body exhaust manifolds with 24-inch extensions360:Stock '77 360 iron log-style exhaust manifolds with 24-inch extensions340:Stock '70 340hp exhaust manifolds with 24-inch extensionsSHT:Hedman 151/48-inch-tube shorty headers with 24-inch extensions 1 58: Hooker Competition 1 58-inch ceramic-coated header tti: Tube Technologies Inc. 1 58x1 34-inch chrome step header 1 34: Hooker Super Competition 1 34-inch header; bare, uncoated
Horsepower
RPM318360340SHT1 58tti1 34
2500186185187189187189187
3000223223225226228228226
3500269271272276280281279
4000299301306307314318312
4500311313315321319326321
4600311314315320317327319
5000303304308315312316311
5400281291289295282296289


Dyno Results
Westech Engine Dyno Superflow 901
Torque
RPM318360340SHT1 58tti1 34
2500391.3389.5392.0396.1392.9397.4392.3
3000389.0390.1394.3396.5398.4399.5395.8
3500403.0407.1408.3414.5420.5421.1418.3
3700400.2404.7409.1413.7423.9425.5420.7
4000392.7395.5401.2403.4411.9417.4409.9
4500362.6365.8367.1374.1372.7380.9374.3
5000318.4319.5323.7330.7328.1331.6326.3
5400273.2283.5281.4286.6273287.6281.3
 
Headers had decent gains on this mild 360 @ 5:35 ish (time)



Not so much on this magnum

 
340 with basic mods

https://www.motortrend.com/articles/mopp-0102-1970-340-high-performance-mill-dyno/
Phase 1:Stock 340 baseline, Chrysler electronic ignitionPhase 2:Replace small production AVS with Edelbrock 800 CFM carbPhase 3:Replace factory HP manifolds with Hooker 151/48-inch headersPhase 4:Replace factory iron 340 HP intake with Edelbrock Performer RPM Air GapPhase 5:Replace SSI springs and retainers with Engle #604LS retainers and #993 springsPhase 6:Replace stock 340 HP cam with Comp Xtreme Energy 268

Dyno Results
Westech Performance Group
Superflow Dyno
Horsepower
RPMPhase 1Phase 2Phase 3Phase 4Phase 5Phase 6
3000185.2195.5199.6206.4206.2214.7
3200195.4206.1213.9220.7220.8229.3
3400208.9224.6233.0240.6240.5251.5
3600224.8238.7252.7260.8259.9275.7
3800236.4253.7266.6277.0276.9298.1
4000249.5267.6280.0291.8291.8311.7
4200259.3278.9292.9306.0306.2327.1
4400265.0287.1304.3321.3321.3344.6
4600268.8297.2313.3335.2334.7355.9
4800274.7306.8321.1343.1342.5366.7
5000278.5312.7329.1352.6350.4377.0
5100280.2316.9330.6354.5352.4381.3
5200281.3316.9330.8353.6353.6384.3
5400273.7314.9329.3350.8355.4386.1
5500273.5313.9330.4350.7355.9387.4
5600269.3314.5330.2350.9353.5389.4
5700312.7329.3348.6353.3391.6
5800308.8326.2347.6351.4387.2
6000329.2353.4383.7
6200314.8373.7
Torque
RPMPhase 1Phase 2Phase 3Phase 4Phase 5Phase 6
3000324.2342.3349.5361.4361.0375.8
3200320.7338.3351.1362.3362.3376.4
3400322.7347.0359.9371.6371.5388.4
3600328.0348.2368.7380.4379.1402.2
3800326.8350.7368.4382.9382.7412.0
4000327.6351.3367.6383.1383.1409.3
4200324.3348.8366.3382.7382.9409.0
4400316.4342.7363.2383.5383.6411.4
4600306.9339.3357.7382.7382.1406.3
4800300.6335.7351.4375.4374.8401.3
5000292.6328.5345.7370.4368.1396.0
5200284.1320.1334.1357.2357.1388.1
5400266.2306.3320.3341.2345.6375.5
5600252.6295.0309.7329.1331.7365.2
5800279.6295.4314.8318.2350.6
6000288.1309.3335.8
6200266.7316.6
 
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