Headers vs 340 manifolds

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In my humble opinion....
You will make more power with headers. The OP wanted to know how much. My answer to that is: it's combo dependant, so we CANT answer his question. Also, whether headers are worth it, or desirable, is entirely dependant on the individual.
So: if you want headers, buy em. If you want manifolds, use them. Just know you are giving up SOME power. How much depends on how much motor.
Simple, really.
 
33IMP said:
In my humble opinion....
You will make more power with headers. The OP wanted to know how much. My answer to that is: it's combo dependant, so we CANT answer his question. Also, whether headers are worth it, or desirable, is entirely dependant on the individual.
So: if you want headers, buy em. If you want manifolds, use them. Just know you are giving up SOME power. How much depends on how much motor.
Simple, really.
Click to expand...
Right! Putting headers on one means you need to make many changes in order to take FULL advantage of headers. This is why people argue headers add "only" 10hp, which we all know is bullshit, because if you RETUNE the engine to take full advantage of headers, you will have more then 10HP difference. How much depends on the rest of the engine. But headers can affect everything from carburetor tuning to distributor tuning and lots of other things. It's all about the complete combo and adding headers CHANGES that combo, so be prepared to make other changed to take advantage of them.
 
When I got my '72 Dodge truck with a 360 the exhaust manifolds were badly cracked. I put headers on instead of manifolds after seeing the Richard Holdener Dodge 360 video, fortunately since my truck is pretty high off the ground cheaper headers fit well and don't drag (went with uncoated Hedman 1 5/8" long tubes). The mid-range torque gains were pretty substantial even with the stock 2-bbl cam as you can see in the video. One point to add, they don't just help at WOT either; I got noticeably better part-throttle torque and throttle response. As far as the typical downsides, I've had these headers on for a year and a half and they've never leaked with Percy's/Taylor Cable soft aluminum gaskets and spark plug access is arguably better than with the stock log manifolds. I drive the truck in all seasons and weather too btw.
 
i don't know myself so go to the guys that specialize in these things.
For what it's worth when Ultradyne ground the cam for my 372
they told me headers wouldn't make a noticeable gain unless the
cam had a duration over .220 @ .50 and a lift of at least .5 inch if that helps.
 
RustyRatRod said:
Right! Putting headers on one means you need to make many changes in order to take FULL advantage of headers. This is why people argue headers add "only" 10hp, which we all know is bullshit, because if you RETUNE the engine to take full advantage of headers, you will have more then 10HP difference. How much depends on the rest of the engine. But headers can affect everything from carburetor tuning to distributor tuning and lots of other things. It's all about the complete combo and adding headers CHANGES that combo, so be prepared to make other changed to take advantage of them.
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did you watch the second video he rejetted the carb and the timming it made 291 with manifolds and 301 after jetting the flipping carb and tunning the pos
pretty simple
 
a-bodyguy said:
did you watch the second video he rejetted the carb and the timming it made 291 with manifolds and 301 after jetting the flipping carb and tunning the pos
pretty simple
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I wouldn't have posted that if that's the best I could tune.
 
33IMP said:
My guess Is he doesn't even know he did it. Scrolling error.
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Oh right good point, I forget that happens sometimes. I do that on my phone once in a while but I usually catch it and undo. Just edited the question to not sound pissed lol.
 
MopaR&D said:
Oh right good point, I forget that happens sometimes. I do that on my phone once in a while but I usually catch it and undo. Just edited the question to not sound pissed lol.
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99% of the time, I'm on my phone while here. Done it myself, more often than I'd like to admit.....
 
33IMP said:
99% of the time, I'm on my phone while here. Done it myself, more often than I'd like to admit.....
Click to expand...

I read threads on my phone but hate typing on touch screens so most of the time when I want to reply to something I use a PC with an actual physical keyboard lol.
 
MopaR&D said:
@autopar3000 what do you disagree with?
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Lol, 33IMP is right. Must have tapped the disagree button when scrolling by.

For the record, I'm a header guy; I have never had manifolds on my car. I was starting from scratch with nothing, so I wasn't about to go looking for manifolds when I could go looking for headers instead.
In the late 90s I started with the same cheap headers you have on your truck, then I went to the shorties that were tested in the magazine article that was posted earlier in this thread, and for the last 10 years or so I've been running coated Doug's D453 headers.
 
autopar3000 said:
Lol, 33IMP is right. Must have tapped the disagree button when scrolling by.

For the record, I'm a header guy; I have never had manifolds on my car. I was starting from scratch with nothing, so I wasn't about to go looking for manifolds when I could go looking for headers instead.
In the late 90s I started with the same cheap headers you have on your truck, then I went to the shorties that were tested in the magazine article that was posted earlier in this thread, and for the last 10 years or so I've been running coated Doug's D453 headers.
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Haha no worries.

I have a set of D453's I bought last November for my Duster with an AutoZone discount as I knew prices were going to go up from inflation. Still haven't installed them yet but I'm excited to see how the performance will improve, the Duster currently has Hedman Tight Tubes going into 2 1/4" downpipes that snake down then up and over the steering linkage. Not very ideal and considering the 360 in that car has heavily ported Edelbrock heads and a custom-grind Racer Brown hyd roller cam (5.9L Mag short block, cam specs shown below) I think it will pick up quite a bit with a proper set of long tubes.

20210727_184130.jpg
 
MopaR&D said:
Haha no worries.

I have a set of D453's I bought last November for my Duster with an AutoZone discount as I knew prices were going to go up from inflation. Still haven't installed them yet but I'm excited to see how the performance will improve, the Duster currently has Hedman Tight Tubes going into 2 1/4" downpipes that snake down then up and over the steering linkage. Not very ideal and considering the 360 in that car has heavily ported Edelbrock heads and a custom-grind Racer Brown hyd roller cam (5.9L Mag short block, cam specs shown below) I think it will pick up quite a bit with a proper set of long tubes.

View attachment 1716009430
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I would be real interested in hearing the results of the Dougs vs the Hedman shorties.
 
Furious65 said:
I would be real interested in hearing the results of the Dougs vs the Hedman shorties.
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From me? Or from MopaR&D?

From my end I can tell you I noticed more difference in the sound than the power. I was running a worked over 318 at the time; small valve J heads, LD340. I don't remember the cam specs, but just to give you an idea it wouldn't support power brakes.

With the Doug's it seemed to feel like I was getting a bit more power throughout the range, but when you spend $850 on something you have to watch for psychology creeping in and making you see things that aren't there. The Doug's are coated so I'm sure temps are down under the hood, but I didn't actually notice that either.

Bottom line, those Headman shorties perform way better than conventional wisdom would suggest they should.
 
autopar3000 said:
From me? Or from MopaR&D?

From my end I can tell you I noticed more difference in the sound than the power. I was running a worked over 318 at the time; small valve J heads, LD340. I don't remember the cam specs, but just to give you an idea it wouldn't support power brakes.

With the Doug's it seemed to feel like I was getting a bit more power throughout the range, but when you spend $850 on something you have to watch for psychology creeping in and making you see things that aren't there. The Doug's are coated so I'm sure temps are down under the hood, but I didn't actually notice that either.

Bottom line, those Headman shorties perform way better than conventional wisdom would suggest they should.
Click to expand...

I think he was referring to me since he quoted my post but still worthwhile to read your experience. I paid around $650 for my coated D453's including shipping as I used AutoZone's 15% off deal and ordered them last December before all the recent inflation.

I think for my case most of the gains will come not necessarily from the difference in the headers themselves but the fact that currently it has 2 1/4" downpipes coming off the shorty collectors with really tight (although smooth and mandrel-bent) curves going down then 180° up then 180° down again to clear the steering linkage. The secondary tuned length is very important on cross-plane V8s, moreso than the primary and having 3" pipes coming straight off the collectors on the Doug's going back a few feet is much more ideal. The Hedman shorties have 2 1/2" ID collectors so having the pipes neck down to 2 1/4" right there and at an angle kinda kills any exhaust gas velocity and pulse tuning that otherwise could be taken advantage of.
 
autopar3000 said:
From me? Or from MopaR&D?

From my end I can tell you I noticed more difference in the sound than the power. I was running a worked over 318 at the time; small valve J heads, LD340. I don't remember the cam specs, but just to give you an idea it wouldn't support power brakes.

With the Doug's it seemed to feel like I was getting a bit more power throughout the range, but when you spend $850 on something you have to watch for psychology creeping in and making you see things that aren't there. The Doug's are coated so I'm sure temps are down under the hood, but I didn't actually notice that either.

Bottom line, those Headman shorties perform way better than conventional wisdom would suggest they should.
Click to expand...
I was specifically asking MopaR&D as I saw he was going from the shorties to the Dougs. However, anyone who has done both is more than welcome to chime in and your input is much appreciated.

The reason I asked is that I have a mild 300hp 318 (ie; built from the old 318 Street Recipe mag article) and have been debating on which way to go for my Barracuda that will be 99% street and I later plan to do a Gen III swap. The shorties are a lot cheaper and would probably be fine for what I'm doing I think.
 
The true improvement is when the headers are open.
Go get a coupla timeslips with the exhaust system hooked up, then go uncap the headers and make a coupla runs, - be prepared for a real difference . .
You will definitely feel a big difference and the timeslip will prove it.
If you have a set of collector reducers, as used connecting the exhaust pipes, - put them on, and see how much you slow down, no Dyno required, just your *** ! !
 
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Furious65 said:
I was specifically asking MopaR&D as I saw he was going from the shorties to the Dougs. However, anyone who has done both is more than welcome to chime in and your input is much appreciated.

The reason I asked is that I have a mild 300hp 318 (ie; built from the old 318 Street Recipe mag article) and have been debating on which way to go for my Barracuda that will be 99% street and I later plan to do a Gen III swap. The shorties are a lot cheaper and would probably be fine for what I'm doing I think.
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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.
 
inertia said:
The true improvement is when the headers are open.
Go get a coupla timeslips with the exhaust system hooked up, then go uncap the headers and make a coupla runs, - be prepared for a real difference . .
You will definitely feel a big difference and the timeslip will prove it.
If you have a set of collector reducers, as used connecting the exhaust pipes, - put them on, and see how much you slow down, no Dyno required, just your *** ! !
Click to expand...

That's where collector extensions are key. Gotta keep the velocity up in the collectors or else there isn't much scavenging going on until higher RPMs. Most "race" headers have noticeably longer collectors for this reason.
 
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 .
 
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