440 through manifolds, 2.5" or 3.0" exhaust?

[dodgeboy440]

Manifolds are 2 3/8" i.d. i'd do 2 1/2" pipes. Manifolds don't like a bunch of valve overlap. You might be surprised at how well a lesser cam will perform with manifolds.

RIGHT !!

So many Gearheads like us get Lost In The

Discussions on Size ….. for a guy bigger is

Always better ?!?!? Not so Sherlock ……

Study for a minute ……,OR Two …..

“ Volumetric Effeciency” ……

Question? IF By Chance YOU All Knowing Grand Puba Of The HP2,3,4,5,&6 …..
Had Exhaust Ports the size of a 55 Gallon Drum would your Ride Perform ?
Or……. Would it be a slug of iron ?

Answer Here Please :______________________________________________________________________

OEM’s over the years have spent countless hours & invested $$$$$$$$$ in determining
What works in a manner of speaking.
You & I benefit from those investments.
How you ask?
By studying what the factories have done. &
Looking for ways to improve the effectiveness of their engineering methodology.

Look For an Example At “ Smokey Yunick “
& some of his out of the box solutions to
Performance…….

Cool Stuff & Mentally Stimulating For Those with a brain ………That’s What Hot Rodding is all about !

Personally & IMO with OEM Manifold’s a 2.5
Size would give you 2 advantages…..

One is less restriction which is always good &
You may want to pair the intake with a low restriction air intake setup to balance the low
Restricting exhaust…….

Secondly the 2.5” over the 3” will fit more
Closely if you will on a street car & thereby
Providing more ground clearance. Ask the
Guys with the deep sump oil pans how their
Driving habits are on the streets…..
You’ll figure it out sooner or later , we all do!

Hope that helps !

Mopar2ya!!

John

 

[Budnicks]

I see you're settled on a 2.5" system

good luck & have fun

I have 68 HP iron ported/smoothed out castings/manifolds
on my current 68 RR
& TTI 3" head-pipes to a full 3" Flowmasters American Muscle 'mandrel system',
H-pipe (already on the car) with/thru Delta 50 series mufflers
& matched 3'' tailpipe up & over the rear, all the way out the back, cut to a 45* angle...

I probably have a bit more cam
(wasn't intending on using the HPs, my $1,000 Unisteer Rack 'bolt-in' steering dictated it,
TTI 383-178c4 (?) is the only Header to fit & are $1,300+)
& Edel. RPM 84cc Combustion Chambers pocket ported cylinder alum heads,
with Super Gold 1.6:1 rockers/shafts, matched springs etc. etc. etc.
but the stock iron HP manifolds (are org. to the car, now ported)
still knocked the heck out of the power, low end especially,
the porting helped a lil' still knocked 'the balls' out of it...
but;
the sound isn't bad at all, no drone
& sounds like a real muscle car should, just not a quick as it can/should be
it's tough giving up 50-ish HP, knowing it too...

 

[1 Wild R/T]

I see you're settled on a 2.5" system

good luck & have fun

I have 68 HP iron ported/smoothed out castings/manifolds
on my current 68 RR
& TTI 3" head-pipes to a full 3" Flowmasters American Muscle 'mandrel system',
H-pipe (already on the car) with/thru Delta 50 series mufflers
& matched 3'' tailpipe up & over the rear, all the way out the back, cut to a 45* angle...

I probably have a bit more cam
(wasn't intending on using the HPs, my $1,000 Unisteer Rack 'bolt-in' steering dictated it,
TTI 383-178c4 (?) is the only Header to fit & are $1,300+)
& Edel. RPM 84cc Combustion Chambers pocket ported cylinder alum heads,
with Super Gold 1.6:1 rockers/shafts, matched springs etc. etc. etc.
but the stock iron HP manifolds (are org. to the car, now ported)
still knocked the heck out of the power, low end especially,
the porting helped a lil' still knocked 'the balls' out of it...
but;
the sound isn't bad at all, no drone
& sounds like a real muscle car should, just not a quick as it can/should be
it's tough giving up 50-ish HP, knowing it too...

My thinking is, this being a vert, I'm not looking to have the fastest car on the street, or the track... The 440 is gonna have 915 heads with a DIY port job, lightweight forged pistons & H beams.. 9-1, 236@.050... So it should be healthy enough for what I'm doing... 3" makes things tight around the differential & the torsion bars... It found a new home quickly & I think th 2.5" is all I need...

 

[69ChargerR/TSE]

I’m using 2 1/2” with manifolds. 11.20s @ 121+ mph. 3.23 gear.

the 2 1/2” pipes just doesn’t seem to hurt power much. Probably less because you going with a cam for manifolds.

What’s done to your engine and transmission?

 

[BSB67]

What’s done to your engine and transmission?

508 cu.in.
Eddy heads
Dual plane intake
Pump gas friendly
Small roller cam w/ 48* overlap

TG2 shift kit, full automatic shift.
Steel drums for safety
2800 rpm converter

With the stock, 1700 rpm converter it ran 11.60-70s at 121+.

 

[Budnicks]

My thinking is, this being a vert, I'm not looking to have the fastest car on the street, or the track... The 440 is gonna have 915 heads with a DIY port job, lightweight forged pistons & H beams.. 9-1, 236@.050... So it should be healthy enough for what I'm doing... 3" makes things tight around the differential & the torsion bars... It found a new home quickly & I think th 2.5" is all I need...

I understand completely

yeah
with stock-ish heads, it should be fine too,
as long as the;
exhaust valve, 'isn't a bigger diameter than the exhaust port'
that's usually where it kills power
you need an opening at a min. the diameter the size or bigger
than the diameter of the exhaust valve or it will rob unnecessary power

people ignore 'that rule of physics', all the time, & it kills power
unnecessarily kills power, good bottom end power where street driving is

& the reversion/pulsation back pressure, in the exhaust manifolds, doesn't help
that's why tube headers make more torque & HP,
it keeps that crap farther away from the cylinder heads/combustion chamber
a 'dual pattern cam' with more exhaust duration, can overcome a lil' of that too

I'm sure it'd be fine for what you're doing still
Just pointing out facts

 

[69SuperBee451]

I never understood running pipes that are a larger diameter than the outlets on the manifolds. Whats the point?

 

[33 IMP]

I never understood running pipes that are a larger diameter than the outlets on the manifolds. Whats the point?

I don't have a degree in flow dynamics, but.....
As I understand it, gasses expand into the larger pipe, causing a pressure drop, helping to evacuate the manifold.
I'm more than willing to listen to a better explanation by somebody smarter than me.

 

[71RRHI]

On my 70 Coronet convertible 440 4speed with Hp manifolds. I put a TTI 2.5" kit with x pipe. I like it. It has a nice low rumble but not real noisy when cruising around with the top down.

 

[Some Car Guy]

I don't have a degree in flow dynamics, but.....
As I understand it, gasses expand into the larger pipe, causing a pressure drop, helping to evacuate the manifold.
I'm more than willing to listen to a better explanation by somebody smarter than me.

I believe that is roughly the ray evernham way of looking at it. He says to step the exhaust bigger as you go. Bean counters dictate going smaller to save a buck. We probably aren’t talking about any huge swings either way, at least not in a street car, but for a max effort deal, you go big or go home.

 

[493 Mike]

Most tailpipes can be more efficient if one size smaller than the exhaust pipes. The gases cool in the muffler, thus reducing in volume. The smaller tailpipes maintain the smaller volume of gases at a similar flow rate, maintaining efficiency. OEMs did this, and it saves $$$ and weight.
Mike

 

[INTMD8]

I never understood running pipes that are a larger diameter than the outlets on the manifolds. Whats the point?

It could be more efficient. If you have say, 2.25 outlets on the manifolds and run 2.25 exhaust, the exhaust will have smaller inner diameter than that on the bends. So, could be beneficial to use the next size up.

Sounds like this setup would be fine with dual 2.5. I think that size is ok for up to 600hp or so.

I have dual 3" on mine. 650rwhp and traps 127+ at 4,270 race weight.

 

[69SuperBee451]

It could be more efficient. If you have say, 2.25 outlets on the manifolds and run 2.25 exhaust, the exhaust will have smaller inner diameter than that on the bends. So, could be beneficial to use the next size up.

That’s a good point when ya think about it like that.

 

[493 Mike]

That’s a good point when ya think about it like that.

That is why premium systems utilize mandril bends. And why I build my systems with them.
Mike

 

[Kern Dog]

Most tailpipes can be more efficient if one size smaller than the exhaust pipes. The gases cool in the muffler, thus reducing in volume. The smaller tailpipes maintain the smaller volume of gases at a similar flow rate, maintaining efficiency. OEMs did this, and it saves $$$ and weight.
Mike

More efficient?
I'd argue that point. Your words have the sentiment that the system is actually better with the smaller tailpipes. I'd contend that beyond the mufflers, going one size smaller doesn't help or hurt and that the reason the factory did it this was was entirely based on cost.

 

[493 Mike]

More efficient?
I'd argue that point. Your words have the sentiment that the system is actually better with the smaller tailpipes. I'd contend that beyond the mufflers, going one size smaller doesn't help or hurt and that the reason the factory did it this was was entirely based on cost.

What are you basing your argument on then?
Mike

 

[BSB67]

That is why premium systems utilize mandril bends. And why I build my systems with them.
Mike
View attachment 2005359View attachment 2005360

That is a thing of beauty.

 

[1KoolBee]

This was a good test -

Ya that is a great test, I’ll bet they could have gotten back 10 hp on the 2.5 test if they jetted the carb for that setup.

 

[33 IMP]

Ya that is a great test, I’ll bet they could have gotten back 10 hp on the 2.5 test if they jetted the carb for that setup.

They were horrified that the 2 1/2 cost almost 20 hp. I was pleasantly surprised. I expected much more hp gone away.
That's evidence how GOOD those magnaflow mufflers are.
I'd bet cheap turbos would have cost fifty hp.
(I have long-*** straight-thru 3" magnaflows on one of my big blocks.)