headers ?? pro and con
 

all;
i am considering headers for a hot street engine. 2.4 - 2.7L (haven't decided yet) & webers. heat to the interior is not an issue. 1 1/2" ?? 1 3/4" ?? Bursch ? is there such a thing as OEM ? comments on the units in the pic, please. ('73 RS ?) all help greatly appreciated.
best
jerry
http://forums.pelicanparts.com/uploa...1110316435.jpg

Pros: Lightweight, more power, cool look & sound.

Cons: No heat. Harder to confuse with a cat & therefore more likely to get you red-flagged in emissions testing. Also, headers may pass more heat on to the engine, so you may see small increases in operating temperatures when not at speed.

Also, what you've got there just look like a standard set of HEs with the boxes cut off. As a header, they're about as good as it gets. SSIs are, of couse, the best. Bursch ones I hear rust out but may be good for the money. You probably want to just go with the stock size (I believe 1 5/8), anything bigger and you'll kill your low-end torque.

How hot will this engine be?

1 5/8 OD Headers.

For a 2.7 hot or not you can't do much better than SSIs their primaries are 1 1/2" OD( 1 3/8" ID ), wt ~24#s,


Mild steel like Bursch uses will quickly corrode.

I am running 1 1/2 OD on my 2.0L race Motor. Wont 1 1/2 on a 2.7 motor choke it down too much?

Most of the guys racing with us are using 1 1/2 on the 2.0L race motors and 1 5/8 on 2.4 above.

No, it's better to be a tad small than big, as w/ brakes smaller is advantageous, the smallest diameter pipe that will pass the gas at peak rpm and load is what is wanted, there is more to it than that but that is a good starting point, other things like primary length, transitions, collector design and size all enter into the equation. Most of us need to buy off the shelf anyway.

When you start getting into race 3.2s 1 5/8 OD is starting to get useful.

Gents;
thank you all for the feedback. i really appreciate it. after 25 years of 4-cylinder bliss i am pretty new to 911's, but learning fast thanks to guys like you and this board. is it my imagination or are the units in the above pic NOT the same as stock units for the same vintage ? they appear as though each tube is of the same (approximate) length, a concept i understand.
comments ?
thanks again
best
jerry

Early cars came with near-equal-length headers. And as a bonus, you got heater boxes around them (handy for foggy windshields).

SSI's are hard to beat. And as a bonus, you get heater boxes with them (handy for foggy windshields).

I am running 1 1/2" on mine....I am running on the street, if you run on the track with a racing muffler you can get away with bigger...just my $0.02

Right, not more power with headers since the SSIs _are_ headers. But true headers will be a bit lighter in wt. So if you live in SoCal and don't travel there is a benefit.

Somebody should make these things out of Ti like on the new vette's...

so... the units in the pic are the same as the ones on my '69 (minus the heater boxes) ?
thanks again all!
best
jerry

Yup. They look like a pre '74 heat exchanger with no boxes. This should be the same as what you've got on your '69 less the boxes.

Unless you never go out in the rainly season (street or track) you DO need heat in the Bay Area. I just did an event at Sears and it was raining on and off. It would have been impossible to keep my windshield clear without heat with both windows down. It also would have been uncomfortably cold.

Stock HE or SSI are my vote.

George

help me understand...let's say i remove the heater boxes from the stock heat exchangers on my old 2.2 longblock. this would be an inexpensive alternative to buying headers?

Bob, I suppose it would be an inexpensive alternative to buying "headers," but what will you gain by removing the heat exchanger boxes from the primary tubes? In theory, SSI's are headers to begin with, as are early style heat exchangers. When I think "exhaust header" it's just the part of the exhaust which bolts to the exhaust ports ("tail" pipe is at the other end of the exhaust) . There are cast iron headers, like american V8 trucks use, and there are tubular headers like high performance american V8's use. I would still call what an SC or Carrera has a "header," it's just that it is not a high performance, tubular header like an SSI is. Of course, for a certain application there might be a different brand/style of header that is better than an SSI header. If you look inside an SSI, it looks quite similar to the "header" pictured at the top of this thread. I think a lot of people use the term "header" to mean high performance (i.e. tubular) header, where as I have always known the term in a more broad sense.

Yes, thought the SSIs are going to be more nearly equal length.

thanks guys. running SSIs on my new 2.7 but still have my 2.2 hanging out in the garage. the hearter boxes on the stock HEs are starting to rust out but the pipes are functional. may be a good solution for converting to headers with a little work and ceramic coating.

If you're looking for an immediate, low cost solution, you've got it sitting in your garage then. Sand blast, paint, and you're in business.

Okay, here is the nomenclature:

All 911s have headers. They just happened to be covered by metal to make them also 'Heat Exchangers'. The early cars have better headers, because they tried to keep them equal lenght and also have a sane routing, not having to go through a single cat.

The "opposite" of headers are cast iron manifolds, that mostly do not have individual runners. This is something you find on non P cars a lot. Here is a lot of power to be found if you change these manifolds to headers.

As usual, Porsche already found a lot of power for us and it is hard to top off the factory. This may not be true for smog era cars, but it certainly is true for the early cars that had close to equal length tubing and good routing on the exhaust.

George

HI,

My stock 2.7RS engine (S cams, MFI, etc) was dyno'd with 1.5" SSIs and then with 1 5/8" RSR style headers.

The 1 5/8" do have more HP and rae stronger above 6K but very poor at lower RPMs. Not good for autox or street.