Headers vs 340 manifolds

[Furious65]

I think you'll be fine going with shorties although you want ones that aren't "block hugger" type with the outlets pointing straight down; having the outlets angled backwards instead will be a great benefit because you can have smoother bends with the downpipes and keep them the same ID as the collectors. I had to use angled collector extensions from Sanderson iirc to make it all fit with the Hedman Tight Tubes which required the diameter to neck down right off the headers.

I was only considering the Hedman 78500 vs the Dougs D453. Those generic block huggers just aren't worth the hassle even if you could get them to fit.

I've seen and worked on a coupla vehicles with the shorty headers, and would like to see any shorty header to pipe connection on the driver's side that doesn't take a lotta fabrication, and doesn't end up looking like the plumbing under a kitchen sink, as I mentioned in an earlier post.
I very much doubt any come near tuned, have so many tight restrictive u-bends, and I had to fab that drivers connection on ONE set , it took longer than installing efficient long tubes, at near the same cost ! !
JMExperience .

Eh, all that matters to me is that it works and I have great ground clearance. Honestly I think I can do the Hedman shorties considerably cheaper than some Dougs since I can do all the fabrication and welding myself.

 

[Inertia]

Depends on the value you put on your time .

Please post a pic of the finished head pipe, I'd like to see it .

 

[MopaR&D]

I was only considering the Hedman 78500 vs the Dougs D453. Those generic block huggers just aren't worth the hassle even if you could get them to fit.


Eh, all that matters to me is that it works and I have great ground clearance. Honestly I think I can do the Hedman shorties considerably cheaper than some Dougs since I can do all the fabrication and welding myself.

The 78500 are what I have. I found some old pics of when I fabbed the downpipes. The installed pic sucks but you can kinda see how it snakes around the steering linkage. And yes the paint changed color after being run lol.

 

[65 Cuda 340]

Had to check to make sure I had not already posted in this thread. Back in the late 70s-early 80s, I had a 73 Duster 340. Stock except for a spread bore Holley, it ran 15.05 at about 93-94. Put on a cheap set of Black Jack headers, no other changes, ran 14.40s at 98 despite now having a serious traction problem with its open rear (3.21 ratio). Just a sure grip would have got me into the 14.20s. I was amazed at how much faster this almost totally stock low compression motor was with headers.

Fast forward to 8-10 years ago. I sold the early model 340 hi-po manifolds I was running on the 360 in my 67 Barracuda, got rid of the muffler shop 2.25 exhaust and replaced it all with TTI step headers and TTI 2.50 inch X-pipe system. Again, a low compression motor, albeit with thin head gaskets and heads milled.030 (but the pistons are .100 down at TDC). Cam is a Mopar Performance 761, which is basically one step above stock. Again, I was amazed at how much more power it had - everywhere. No traction at all anywhere in low gear; had to swap to drag radials (for the street) because it was scary to drive with street tires (I think roads around Tallahassee are slicker than farther north, maybe heat/humidity). No times, because I haven't been to the strip since, but no question it was a huge improvement.

So then I bit the bullet and put TTI headers/2.5" exhaust in my 65 Barracuda. Now that was a job. Cam is the same as in my 67 Barracuda, compression ratio is higher. Again, big improvement.

So, I simply don't believe any test that says headers are only worth 10 hp. Maybe with a .380 lift cam. ??

Just my own experience. Yours may differ.

 

[340sFastback]

With stock manifolds the driver side head pipe, at least the stock style pipes, are severely pinched down to clear the torsion bar. TTI routes the driver side pipe differently to get rid of the pinch. So in a lot of cases some of the gain with headers is alleviating that pinched head pipe.

 

[Inertia]

The real difference is when you uncap them, disconnect the ex pipes, that'll put a real smile on your face ! !

 

[Bodyperson]

With stock manifolds the driver side head pipe, at least the stock style pipes, are severely pinched down to clear the torsion bar. TTI routes the driver side pipe differently to get rid of the pinch. So in a lot of cases some of the gain with headers is alleviating that pinched head pipe.

That’s why the dyno tests are not all telling.

 

[340sFastback]

That’s why the dyno tests are not all telling.

Can't speak for the various dyno test comparisons done over the years. But I think a more valid comparison is using an unpinched driver side head pipe when testing the manifolds. Also passengers side heat riser could be partially stuck closed too which would choke power too.

 

[Bodyperson]

Can't speak for the various dyno test comparisons done over the years. But I think a more valid comparison is using an unpinched driver side head pipe when testing the manifolds. Also passengers side heat riser could be partially stuck closed too which would choke power too.

That’s what I’m saying. The manifold vs. header comparisons do not account for the torsion bar squeeze.

 

[65 Cuda 340]

My 73 Duster (post 129) benefited to some extent just from getting rid of the torsion bar pinch, as well as the tiny pipes coming off the manifolds. But neither my 65 nor 67 Barracudas had that pinch or the small pipes - just full 2.25 pipes off the manifolds. Of course, the latter two also benefitted not only from headers, but also from increasing the pipe size from 2.25 compression bent to 2.5 mandrel bent. But I'm convinced the headers were the main gain.

 

[stroked340]

TTi's all the way we use to throw stock manifolds in the trash along with Thermo-bogs!!

 

[HSDemon]

Had to check to make sure I had not already posted in this thread. Back in the late 70s-early 80s, I had a 73 Duster 340. Stock except for a spread bore Holley, it ran 15.05 at about 93-94. Put on a cheap set of Black Jack headers, no other changes, ran 14.40s at 98 despite now having a serious traction problem with its open rear (3.21 ratio). Just a sure grip would have got me into the 14.20s. I was amazed at how much faster this almost totally stock low compression motor was with headers.

Fast forward to 8-10 years ago. I sold the early model 340 hi-po manifolds I was running on the 360 in my 67 Barracuda, got rid of the muffler shop 2.25 exhaust and replaced it all with TTI step headers and TTI 2.50 inch X-pipe system. Again, a low compression motor, albeit with thin head gaskets and heads milled.030 (but the pistons are .100 down at TDC). Cam is a Mopar Performance 761, which is basically one step above stock. Again, I was amazed at how much more power it had - everywhere. No traction at all anywhere in low gear; had to swap to drag radials (for the street) because it was scary to drive with street tires (I think roads around Tallahassee are slicker than farther north, maybe heat/humidity). No times, because I haven't been to the strip since, but no question it was a huge improvement.

So then I bit the bullet and put TTI headers/2.5" exhaust in my 65 Barracuda. Now that was a job. Cam is the same as in my 67 Barracuda, compression ratio is higher. Again, big improvement.

So, I simply don't believe any test that says headers are only worth 10 hp. Maybe with a .380 lift cam. ??

Just my own experience. Yours may differ.

The difference that you saw with headers is that headers usually produce more power all over the RPM range with no loss of power anywhere. Most people just look at peak power production and see 9-10HP at 5,500 RPM and think that they are not worth it for 10HP, and to be honest a lot of performance parts that only make 10 peak HP may not really make much of a difference as they only make that power on the top and usually lose mid range torque, like with a single plane intake on a very mild engine. Another thing with long tube header that usually improves, and the dyno cannot account for it, is that you get rid of some of the bad horrible bends and kinks in the tubing right after the exhaust manifolds, that in itself will probably make a good improvement, that you will not see on a dyno, as you are not running stock exhaust tubing. Parts that make more power all over the RPM range, from 2500 to 5500 usually make a good difference in performance. I learned this while working on 5.0 Mustangs in the 80's and 90's. One of the most popular performance accessories, and the one that when I sold them everyone said that the car felt much better and when I drove them after the install I could always fell the difference, were underdrive pullies. The underdrive pulley kits, crank/water pump/alternator, would only make maybe 5-6 peak HP on a 5.0 engine, but the cars definitely felt much better and were faster. The pulleys would make more power from idle to redline, and even though it was not a ton, it was everywhere in the RPM range with no loses anywhere.

 

[66jim]

The difference that you saw with headers is that headers usually produce more power all over the RPM range with no loss of power anywhere. Most people just look at peak power production and see 9-10HP at 5,500 RPM and think that they are not worth it for 10HP, and to be honest a lot of performance parts that only make 10 peak HP may not really make much of a difference as they only make that power on the top and usually lose mid range torque, like with a single plane intake on a very mild engine. Another thing with long tube header that usually improves, and the dyno cannot account for it, is that you get rid of some of the bad horrible bends and kinks in the tubing right after the exhaust manifolds, that in itself will probably make a good improvement, that you will not see on a dyno, as you are not running stock exhaust tubing. Parts that make more power all over the RPM range, from 2500 to 5500 usually make a good difference in performance. I learned this while working on 5.0 Mustangs in the 80's and 90's. One of the most popular performance accessories, and the one that when I sold them everyone said that the car felt much better and when I drove them after the install I could always fell the difference, were underdrive pullies. The underdrive pulley kits, crank/water pump/alternator, would only make maybe 5-6 peak HP on a 5.0 engine, but the cars definitely felt much better and were faster. The pulleys would make more power from idle to redline, and even though it was not a ton, it was everywhere in the RPM range with no loses anywhere.

Yes could not agree more, IMO engines power output should be be measured in area under the curve. A much more real value.

 

[justcuz]

Reading this again since I posted this question 2 years ago

Completely stock 340. 4 speed car 3:23 gears non sure grip

Thinking about long tube headers vs stock 340 manifolds.

Car will be tuned if header installation moves forward.

Realistically, how much gain can I expect?

No other modifications planned.

Asking all the Mopar experts on here.

 

[Inertia]

The 78500 are what I have. I found some old pics of when I fabbed the downpipes. The installed pic sucks but you can kinda see how it snakes around the steering linkage. And yes the paint changed color after being run lol.

View attachment 1716010328

View attachment 1716010329

Thanks for posting that, - good job .

Reading this again since I posted this question 2 years ago

Completely stock 340. 4 speed car 3:23 gears non sure grip

Thinking about long tube headers vs stock 340 manifolds.

Car will be tuned if header installation moves forward.

Realistically, how much gain can I expect?

No other modifications planned.

Asking all the Mopar experts on here.

Take a pic of your grin before, then after install, AND then again when you run them open .
You'll know without question !

 

[496 polara]

Depending on the exhaust behind it I would wager 15hp.

 

[junkyardhero]

i agree, tests have shown a pretty average 15hp throughout the range. there are a lot of variables, but upwards of that 15 wouldn't be unheard of.

 

[1MeanA]

What was the recipe for more power back in the day? Headers, cam, intake and carb? I think it was discussed already in this thread but changing one component won't provide a significant gain IMHO. The stock stuff isn't garbage but it could be improved.

 

[Inertia]

4 bbl, 3/4 race cam, 4:11 gears and headers .

Headers have long been the most cost effective way to gain horsepower.
When headers became popular, advertising would have you believe 10 - 15 % (%) h/p gain, 10% with exhaust hooked up, 15% with them opened up. iirc.

 

[1MeanA]

4 bbl, 3/4 race cam, 4:11 gears and headers .

What the heck is a 3/4 race cam anyway?

 

[Inertia]

What the heck is a 3/4 race cam anyway?

Lol , my memory isn't THAT good. lol
That was the Drive-In talk, - mosta them didn't know either .

 

[junkyardhero]

What the heck is a 3/4 race cam anyway?

basically it's a high performance street cam. it comes from the old school flat head era.

there was "semi race" and "full race" grinds and what they did was grind the intake lobe as full race and the exhaust as semi race, thus it was only 3/4 race.

basically today it kinda encompasses a whole slew of performance cams that are somewhere in the realm of that 3/4 of the way in between hotter than stock and not full race. sometimes people will refer to them as "stage 3" as well.

legendary cam grinders Winfield and Harman-Collins were the ones that are credited with it.

 

[ir3333]

headers on a stock 340 through mufflers aren't going to gain anything noticeable.
3/4 cam was a cam ground specifically for the rpm operating range on 3/4 mile stock car track which would have
no low rpm requirement....or maybe a cam with 12 lobes?

 

[Inertia]

headers on a stock 340 through mufflers aren't going to gain anything noticeable.

Absolutely 100% wrong .
I have had tooooo many customers come back with the biggest **** faced grins after their first drive with headers.
They certainly noticed, not just one, or a few, - - dozens.
Then they go to the strip and open them up and gain up to 5/10ths, or can't get traction .

Any breed.
The power isn't just at wide open throttle, it's at idle, it's at slow cruise, hi cruise, the extra power you don't notice is just less gas pedal thru all driving conditions.
The low back-pressure, scavenging, equal length tubes, doesn't only work at wide open throttle.
Those gains are there in all conditions, otherwise all cars would come with log style exhaust manifolds, no exhaust direction from the head at all, yet they made cast hi-perf exhaust manifolds with direction, then tube headers, all improvements, at a $$ cost.

 

[junkyardhero]

headers on a stock 340 through mufflers aren't going to gain anything noticeable.
3/4 cam was a cam ground specifically for the rpm operating range on 3/4 mile stock car track which would have
no low rpm requirement....or maybe a cam with 12 lobes?

while i won't address the stance on headers, can you shed any light on how you came to that conclusion on the 3/4 cam?