Do headers on a 318 make a difference when adding dual exhaust?

[RicardoA]

I have a 1967 Plymouth satellite with a 318 and I am looking to add duel exhaust. should I also add headers or do they make that much of a difference?

 

[RR Fan Dan]

Nice ride. Why not head over to the welcome wagon and introduce yourself. This thread would be better in the exhaust forum. Are heads ported or stock? Headers really don’t make a big difference until you start trying to squeeze every bit of horsepower you can. Are you running a 2bbl or 4 bbl? If your engine isn’t built than I wouldn’t worry about headers. It will sound good with dual exhaust.

 

[Detective D]

I have a 1967 Plymouth satellite with a 318 and I am looking to add duel exhaust. should I also add headers or do they make that much of a difference?

View attachment 1833010

Fast answer is all the little stuff adds up.
Longer answer is depends on your end goals and budget.
Personally, if I was doing a car like that and was really just looking for sound and a wake up call for the engine, I would find some early 90's 318 Magnum manifolds and go that route. No leak issues, more flow then you will see out of stock heads on any LA 318, no worries about fitment of long tubes or whatnot. I think 91/92 Magnum manifolds are comparable to 340HP manifolds if I remember right. Can probably find a set on FB market or ebay for a lot less then headers too.

 

[68-500]

Headers,dual exhaust,and a 4barrel intake manifold probably biggest return on$ per hp.

 

[68-500]

Fast answer is all the little stuff adds up.
Longer answer is depends on your end goals and budget.
Personally, if I was doing a car like that and was really just looking for sound and a wake up call for the engine, I would find some early 90's 318 Magnum manifolds and go that route. No leak issues, more flow then you will see out of stock heads on any LA 318, no worries about fitment of long tubes or whatnot. I think 91/92 Magnum manifolds are comparable to 340HP manifolds if I remember right. Can probably find a set on FB market or ebay for a lot less then headers too.

Am I mistaken? I thought there was fitment issues with one side when using magnum manifolds.

 

[RicardoA]

Nice ride. Why not head over to the welcome wagon and introduce yourself. This thread would be better in the exhaust forum. Are heads ported or stock? Headers really don’t make a big difference until you start trying to squeeze every bit of horsepower you can. Are you running a 2bbl or 4 bbl? If your engine isn’t built than I wouldn’t worry about headers. It will sound good with dual exhaust.

Thanks for the help. I will go over to the welcome wagon and introduce myself and go to the exhaust forum.

 

[#41]

Its not worth installing headers on a mostly stock 318 unless you are just trying to make things look pretty.

 

[Dutchrebuild]

I just put a dual exhaust on my 68 318 charger...the system was free as it came on a buddy's 67 Coronet 318, and he's going to a big block. My system was built off of a set of 71 340 exhaust manifolds. not sure why they used the 340 manifolds instead of the 318 manifolds. Problem is, the 340 port size is much bigger than the 318. This caused a big headache finding a gasket to seal the big port manifolds to the small port head. I am not a fan of small block headers on b bodies...they tend to hang way to low, and sometimes get banged off the road. I would build a dual exhaust off your original 318 manifolds...it will be just fine. I only got one good run in so far with my dual exhaust setup...sounds much better and I swear it's a bit faster. Good luck!

 

[YY1]

Magnum manifolds don't clear the power steering pump on the driver's side.

360 manifolds could be an alternative, but like 340 pieces, the early ones without AIR holes are hard to find.

Interestingly, the set of 360 manifolds I have are cast different, and the driver's side AIR holes look like they could be tapped and plugs fiitted. The pass side is "D" shaped and look to require welding buildup.
That means you could technically use a 360 Driver's side after installing plugs and a Magnum Passenger side.

The main issue with SBM headers is that they're A- expensive as all get out (at least for good ones), and B- an incredible PITA to install and remove.

The factory said the dual exhaust on 318 73/74 Roadrunners was good for 20 HP.

 

[Hey-O]

You could go with a shorty header. Less hassle, clean bolt and add a little HP and torque.

 

[Runcharger]

Headers aren't worth the trouble on a 318. I would keep the manifolds. No leaks, no dragging pipes. The dual exhaust will gain you the most performance improvement. If later plans include an upgrade to a 360 then the headers would be worth it.

 

[1967coronet]

Yes, headers and duals will both improve your horse power and sound better.

If you have future plans of adding more performance bolt on parts I would have a set of headers in the mix.

Adding a nice set of 2" or 2.25 duals and muffs on your manifolds will make more smiles per mile.

 

[YY1]

The 2.25" duals with factory manifolds completely changed the tone of my 73 318.

I get lots of comments about the sound, and people asking if it's got a cam.

 

[WileE]

Yes, without question.

 

[Unkle Krusty]

Nicks Garage in Montreal has made videos of a 318 with headers, and stock exhaust. On my van the engine is next to me, as in inside. Clearance and heat were the main issues. I stayed with the stock manifolds, but later will change to twin pipes. I have not researched the clearance for any other manifolds, but have heard the 360 manifolds breath a bit better.

 

[Coelacanth]

I did a dual exhaust, 2 bbl-to-4 bbl intake manifold and carb upgrade on a 1968 Monaco 318 winter beater I had, and it definitely made a fun difference! I don't think headers are worth the bother, either.

 

[Unkle Krusty]

I did a dual exhaust, 2 bbl-to-4 bbl intake manifold and carb upgrade on a 1968 Monaco 318 winter beater I had, and it definitely made a fun difference! I don't think headers are worth the bother, either.

I thought I would wait until the current exhaust pipes fall apart and then go the twin pipe route. Fiddling with the new 1405 Edelbrock today. Put in and on their cam and manifold and related bits.

 

[Budnicks]

Any engine will increase HP & torque with a set of long-tube headers
even a set of short tube headers will make more power & torque than stock

any I.C.E. is just a huge air pump, air in & air out
on any engine they don't know what brand or size they are
BB or SB
it's all about flow, what goes in has to come out,
free flowing in & out...
generally the proper sized tube header is worth about 7-10% at min.
even on a completely stock 318 2bbl engine

fitment & clearance is a different issue,
unless they are way too small tube or way too big tube
I highly doubt any headers for any 318-360 LA or Magnum
(Magnum exhaust manifolds will flow better than the LA manifolds, but are made for trucks)
for those engines it is either one of these 1-5/8" diam. or 1-3/4" daim. tube
on the high side
bigger versions will have 2-1/2" std. collectors or 3" on the high side,
some will have reducers down to 2"- 2-1/4"
or 2-1/2" tubing, is on the bigger side for a lil' teen

*even a decent set of headers,
combined with a single 3" exhaust, head-pipe with a Y, into one, good flowing 3" muffler
will make more power, than a stock engine/stock manifolds with 2" duals

*unless it has other mods
like a bigger/higher lift & more duration cam, you'd want headers
&
*An alum 4 bbl intake/dual plane for street,
get an Edelbrock RPM dual plane it's worth it, hands down best street manifold on the market
&
*a single plane/open style intake, is more for wide open throttle,
can still be made to work on the street, just will give up bottom end torque
&
*along w/nice properly sized 4bbl carb or EFI
that will wake up

almost any domestic engine combo, with cast iron manifolds,
from org. OE cast iron stuff,
it's restrictive PERIOD
even the HP manifolds, don't believe the hype
& I speak 1st hand experiences, on either the intake or exhaust...
but with some 'tubular headers',
albeit the shorty will make a lil' more HP/TQ, on the lower side of the scale
but a long tube headers, usually under chassis, will have more HP & a bunch more TQ

Tri-Y's Headers, like Schumacher Industries, are a decent compromise for fitment,
better than the shorty's,
but not as good as a quality long tube

we are talking Small Blocks here too, not a MW
unless you're talking about like the MW manifolds (they are some heavy SOBs)
BBM/RB 413-426 Ply. SuperStock MW or Dodge Ramcharger MW manifolds
they will flow, much like a header would, but not applicable here, & very heavy cast iron

none of the SBM manifolds,
not any of 273 (even HP versions)-318-340 (even 340 HP man.s) or the 360,
in any or either LA or Magnum series
they aren't as good as any tubular headers, would be

watch Engine Masters (MotorTrendTV) series on Headers & exhaust pipes
there's several episodes, they are very informative

Headers will make more power & torque...

 

[RicardoA]

I just put a dual exhaust on my 68 318 charger...the system was free as it came on a buddy's 67 Coronet 318, and he's going to a big block. My system was built off of a set of 71 340 exhaust manifolds. not sure why they used the 340 manifolds instead of the 318 manifolds. Problem is, the 340 port size is much bigger than the 318. This caused a big headache finding a gasket to seal the big port manifolds to the small port head. I am not a fan of small block headers on b bodies...they tend to hang way to low, and sometimes get banged off the road. I would build a dual exhaust off your original 318 manifolds...it will be just fine. I only got one good run in so far with my dual exhaust setup...sounds much better and I swear it's a bit faster. Good luck!

thanks, really appreciate the advise.

 

[1STMP]

Its not worth installing headers on a mostly stock 318 unless you are just trying to make things look pretty.

And sound 'better'. Which depends on
muffler selection.
Few consider custom headers coupled
with seldom considered mufflers such
as Bassani, and instead run with what
everyone else is using.

As a baseline, headers will almost
always net 10 extra Hp, though not
true in every case. Custom headers
are not far beyond the cost of off
the shelf.
Crank up the volume!