Exhaust Manifold vs Shorty Headers

I have always been told that tube headers are always better that stock exhaust manifolds and I believe 99% of the time that is true. But as I was looking at shorty truck headers for my SBC-355, it dawned on me that with the very short travel of these compressed “shorty” headers versus that of stock manifolds or ram horns how much is performance really improved in this case?

I have seen test results of stock manifolds versus long tube headers and I understand that substantial power increases are possible. However the total length of exhaust gas travel before entering the collector on stock manifolds (both non-ram and ram horn) is so small that shorty tube headers actually increase this “travel length”. Is there really that much of a performance difference?

 

from what i read the problem with manifolds is that when a cylinder fires it can force gases still in the manifold into another cylinder causing an incomplete burn i have also seen the tests on long tube headers but none on shorties i would however be lead to beleive that shorty headers would get most exhaust gases at least far enough away from the other cylinders exhaust valves to minimize gases coming in.

 

The performance improvement of shorties is minimal compared to stock manifolds, but there is generally some gains. The tubes are smoother than the rough castings and the bends are gentler than the abrupt turns that many manifolds make. usually the size is a little bit larger as well. All combine for a slight improvement but not as much as a long tube or better yet a properly designed Tri-Y.

 

A lot of it depends on the manifolds you're talking about. If your engine has really restrictive manifolds, the shorties will do a lot of good.

The other thing is collector diameter. Are the shorties you're talking about 2 1/4" collector, 2.5, or 3"? Same for primary diameter.

You can make the higher level arguements about pulse scavenging etc, but there's gains to be had going from tiny pipe to large pipe. Especially when you're talking about a performance engine, not a stocker.

Guesstimating for the average 350 chevy based on experience, a good set of shorties ought to be worth 3/4 of what longtubes gain.

 

It sounds like there may be a point of diminishing return here.

How much is 1HP worth?

Now I will admitt that tubes "look" nicer than a manifold but - my ride is far from show quality!

 

If the question is shorties versus old school manifolds, it's shorties, no question.

If the question is shorties versus longtubes, that's a much closer gap.

What is the question? I'm confused and simple minded. Help me out.

 

I have a 97 Votec 350. It's in a 3500 1 Ton 2wd Dually. I have 2.5 pipe from the cats back and 3" from the cats forward.
I put on a set of JBA SS shorties and think the only difference over the stock manifolds it these are little noisier. I didn't get any "seat of the pants" feel after putting these on so I would guess the adder would around 2/4HP difference.
When I put on the K&N FIPK kit I noticed a real "seat of the pants" difference, compared with
the shorty headers.

IMHO

 

Maybe in some cases you will notice a small difference between factory and shorties, for the most part "it aint there".
I put the FPP shorties on my 97 Cobra and on the dyno it showed not quite 1HP difference fromt he stock manifolds(at the rear wheels), and the difference was above 5kRPM.
I put a set of long tube headers on the Cobra and noticed a 21HP difference at the rear wheels.
Shorty headers in any form except the tuned shorties for SBF mustangs are a waste of time in my book.
As for the tri Y's, they are OK, but for lower RPM's and not as good as a true tuned long tube header.

 

Well it depends on what you want and how you use/drive it. Also how much trouble you want to deal with. If you want no trouble or leaks easy to keep clean then just run the manifolds, sure its boring but an exhaust leak is not that exciting, and cleaning headers is not fun.
If its a heavy car or pulls loads like in a truck, long tubes are gonna rob you of a lot of power and milage on the street, and add loads of power on the high end at the track. Once you get it onto the highway it will be better and average out if you stay long enough.
I had a big pontiac and when I swapped tuned long tubes and tuned it to run, it morphed into a dog in normal street driving and a monster with my foot in the carbs. It was faster on the street and more enjoyable to drive with the manifolds and a lot faster at the track with the long tubes.
The tri-ys realy are the best of both worlds, but as previously mentioned by hotroddon they need to be properly designed. (Thorley I think is one of the better)They will start to increase low end at 17/1800 ish and pull hard at the top end. Big science behind all of that.
The shorties are concidered a waste of time and money by most by them selfs.
ls1truck.com has alot of info and dyno results on shorty headers versus long tubes. Dynos dont give any info on how it will drive, just how hard it pulls at the top thru the lights.
My .02

 

the guys i talked to used shorty headers mainly for clearance issues. put a sbc in a 49'-54' chevy car and you will see why they use them.

 

No.
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I would think that newer factory manifolds (1970 vs 1964) for a SBC would be better, but actual shorty headers probably wouldln't do a whole lot.

Back in the 5.0 days I did a set of equal lengthy shorties, they looked like they flowed a hell of a lot better than the stock 1988 manifolds. Add a cam and they'd help even more.

 

speedway sells some nice looking ram's horns that look traditionalo and supposedly flow well.

 

They used Rams Horns on older Vettes in the '60s, and they're not bad as far as cast iron manifold go. But a lot of cast iron manifolds were like big logs with terrible flow. Shorty headers might not be much better than Rams Horns, but they're a lot better than most of the other stock cast iron manifolds.

Shorty headers make tight installations a lot easier -- that's for sure. Make sure you can get at the spark plugs, because there are variations of spark plug location and angle on some heads.

 

Being a simple, low-bucks kinda guy, I prefer efficient cast iron manifolds over any kind of header. Keeps the engine compartment temperatures down - an important consideration in Texas - and often allows hanging power accessories such as P/S, A/C and/or alternator in a cleaner manner without resorting to billet brackets!

Most cast iron manifolds can be cleaned up with a hand grinder to look smooth and attractive and there's lots to be said for being trouble-free and leak-free. This is an important point if you drive your hot rod more than on and off the trailer!

As for performance, about the only real-world situation where there might be a slight advantage to headers over a good set of efficient manifolds is when passing on a two-lane road at wide-open throttle, where every additional horsepower means an extra margin of safety. But this assumes that the carburetor/cam/ignition/heads combination is optimal, and that the efficiency of the exhaust flow through the manifolds is the weakest link...again at wide-open-throttle.

Just my $.02...

 

That's for a 1997 cobra. Many late model LS-V8 chevys are a very similar deal, because the stock manifolds are so good that anything short of longtubes is a waste.

On my late model LT1 camaro shorty headers were worth a tenth at the strip. Got the timeslips to back it up. LT1s were pretty much the very last generation of cast iron traditional manifolds for chevy V8, everything afterward looks like a header, even if it's cast, and flows much better accordingly.

The other thing to consider is many late model shorties maintain stock outlet diameter so they bolt to stock cat pipes. A header with a 2 inch outlet ain't gonna flow, period. A good shorty with a 3 inch outlet will flow.

On a traditional small block chevy with old manifolds, there's more than one hp to be had.

 

The more overlap you have, the more important keeping the primaries separate is.

 

I highly recommend the CD from Headers by Ed on header design -- great info.

 

AMEN !!!! I agree totally !! The early cast iron look traditional vs the cheapie shorties and will last nine times as long.
A few years ago ASA stock car association had a class where they were required for some time to run cast iron manifolds ( 901 vette cast units with 2 1/2 inch outlets were the hot set up) and a two barrel carb.
A friend of mine in Indiana dynoed these engines for this class. They actualy showed increased horse power over the header set up most were using!!
I bought a pair of cast center dump units sunday at the Indy swap for $40 bucks. A little bead blast and some vht and we are set for ever ...

 

Shifty Shifterton,

I have a friend with an 02 W6 and very nasty 402CI Ls-1. He switched from shorties to long tube and picked up 33HP at the rear wheels (these headers cost over $1k) and he now is turning in the low 11's with a street car and DOT slicks. It depends on what you are building the motor for as to which header will be of the most benefit.

At least my .03 cents worth.

 

Were your friend's shorty headers late model smog legals, the way most are? The kind that terminate in the stock manifold diameter?

Really no suprise that a nasty engine picked that much up with longtubes, it's not an apples to apples comparison where you can say tube length was worth 33 hp. Your friend's new headers undoubtedly have bigger primaries and a bigger collector than the shorties.

When talking header design, you can't include the smog legal variety because they all bolt to the stock cat pipe and have a restrictive collector.

see where I'm coming from?

 

Good discussion and points being made here. So please allow me to throw these questions out there...

1. Stock 305 out of a '95 FS Chevy truck going in a 53 Chevy truck (daily driver type of truck and please don't hassle me about the 305, it was only $100 with less than 40k miles on it), keep the factory manifolds or go with shorties or longtubes? The goal is a jump-in-it-and-go, not every HP that can be made.

2. Mild 355 in a 66 Chevy truck (daily driver type also) that currently has some old, nasty, constantly leak, dimpled-to-hell-to get-em-to-fit, 1 1/2" primary longtubes. replace with some factory manifolds, shorties or go longtube again?

Being that both trucks are never gonna see the strip, would the money needed for the longtubes be worth it? I'm not exactly made of money and let's face it, painted headers are gonna be rusty in about 2 days after they are installed, LOL, so the ceramic coated would pretty much be the way to go.

I saw an episode of Horsepower TV when they tested all kinds of different headers and the gains didn't seem to be very much for the outlay of moolah... But then again I can't remember the exact numbers and that was on a dyno, not real world driving.

 

I design and build custom headers. Shorties are an improvement simply because they don't have such sharp turns and don't converge at one another like manifolds. Manifolds are cheap to produce and that's why they are on your car from the factory. At that length of primary on a shortie, tuning is out of the question so the only gains are due to increased flow efficiency. Long tube headers aren't better because of the name brand but rather what kind of coincidence it is that those off the shelf headers fit your exact engine combo. There is a reason people want custom headers. The reason being that every combo is different and that calls for a different header/intake. Also some floks don't like to fight headers for fit and plug clearance. All headers have a "tune." It's just that is that tune anywhere near the ballpark of what you need. Shorties are a solution to a problem. Cast is ugly, boring and generally ill flowing. Shorties fit better than longtubes. Primary diameter and length are very important and so is colector length. Bigger is not always better. You'd be surprised what kind of power can be made with 1-5/8" primaries! Longtubes, when designed or used properly, are king for efficiency and power. A good header consists of good materials starting with at least a 5/16" flange. All mine start with 3/8" flanges. You don't blow header gaskets because of bad gaskets. I can run my headers with no gasket. They are bad because of the little o ring welded on the engine side of the header flange and that stupid 1/4" stamped flange. They are also bad because you need to be a contortionist to get to your plugs and header bolts. They are also bad if you EVER have to use a hammer to install headers that are made for your car.

 

I've read a number of you guys who think shorties are better looking. I couldn't disagree more. True there is a slight performance edge to the shorties but they have no character. Give me a pair of ram horns any day!

 

They only have no character because they are a fairly new design and are widely used. I would rather see some megaphone headers myself. I think those are cool looking and more period correct.

On the flip side, old school machinery that has a smooth well designed casting is really cool to look at. Just something about a nice casting...

 

Shifty Shifterton,

My friend owns a muffler shop, and he totally redid the stock exhaust system, did away with the Y pipe, made a complete dual exhaust system with two short hi-flow cats. The shortie headers he had looked like equal length shorties (kind of like the 5.0 Mustangs) abundle of snakes is what I call them. Anyway, they were not totally CARB rated, but he got them past with no issues. So when I said he made 33HP more at the rear wheels, this was over the shorties he had on the "real" dual exhaust.
I'm not sure if he is using 3" pipes to the cats and 2.5 the rest of the way, but something like that. I drove the car with the shorties and also drove it afterwards and the difference was like night and day.

 

Conceptfab,

Well put, here are the ones I did for my flathead.
To put it in simple terms, when you build custom headers, you build for that specific motor, and that specific chassis.
I love building headers!

 

Me too! And I REALLY like stainless! 37 Plymouth with, cough cough, small block chev.

 

See all those holes in the frame? I had to run 2-1/2" stainless through all that too, not easy. 1/8" clearance top and bottom

 

if there was any real performance to be gained from hedders on a street driven vehicle i would have thought the oem,s would have them.