No header / extractor or free flowing manifold will ADD power. It will REMOVE a bottleneck if this is the problem, & allow the engine to develop all the power that it can. That power level is completely dependant on the engines ability to ingest & burn fuel. & on its ability to convert that burnt fuel to work output EFFICIENTLY.

The cast GX manifold is NOT all that heavy, & as i have writen, i defy anyone to DEMONSTRATE the measurable vehicle performance loss as a direct result of the additional weight of the GX manifold over the weight of extractors.
Chris

Hmm, amazing thread, but aren't we missing the simple fact that any potential increase in h.p. would be nearly insignificant in real world application?

Re Z22/24 Engines
We should probably start a new Thread, because we seem to have moved marginally away from the original ---GX Exhaust Manifolds (they are better than stock, but HEEEVVY.)
Dodgeman, the link, "Nissan Engines" on the right of your screen will, I think, answer all reasonable questions. Good value and worth a look.

Feral,...Datster
[blushes, scufs foot] Aww shucks fellers, 'twernt nuthin'

89mm
This has been my most enjoyable exchange on this site & it has become obvious that i am able to mix it with others of more advanced years & / or advanced knowledge. I would love to waffle on about my 200B & other adventures, but this is not the spot for it as this is a thread for 1200 GX exhaust manifolds [remember], which i can firmly state are DAMN FINE MANIFOLDS.

Perhaps there is another forum where we can meet as i want to discuss uograding my L20B with Z22 crank, rods & pistons, plus the later 180B twin Hitachis, plus valve seat inserts [200B Gas cyl head?] & cat converter. I like 'em to be Clean, Mean & Legal, & it's the latter one that can be hard to do.
Why not use a Z22 or Z24 engine? I want it to look as original as possible, right down to the original engine number.

If anyone has learned something from this exchange, then my blown out internet bill will be worth it [it takes ages to write & re-check those long ones]
I have never crashed, ever, but i am not a racer, & like you, i am fully aware that i am only 8 feet tall & bullet RESISTANT.
I also concur fully with another of your comments. It seems that the more i learn, the more i realise just how little i know.
Every time i add some new thing to the pile of learning, it just gives me a better view of the size of the ocean of knowledge yet to be absorbed.

Looking foward to more
Chris
P.S. Did i mention just how good GX exhaust manifolds are?
GX EXHAUST MANIFOLDS ARE REALLY GOOD [just to make sure that i stay within the thread.]

Greetings Dodgeman!
It seems to me that the 200B is the old farts car, because that's what I drive, obviously in a little more spirited way than you do, but as you say, to each his own. Mine has a mild cam, a 32/36 Weber (alternatively, 2 X 1-3/4" SU's) and a 2-1/2" exhaust and it goes very nicely thanks.
I've been an engineer in the oil patch for longer than I'd like to say, and I've been building and competing with my own cars since the invention of the wheel, or so it feels. Presently, we are running number 4 (or is it 5?) with a new one on the drawing board.
My wife says that I am still an automotive adolescent--- the only change is that I realise that I am not 10 ft. tall and bulletproof like I was when I was 20, specially after a couple of spectacular crashes, but that's another story.
As I have said previously, I don't mind throwing any ideas or concepts into the middle for discussion and criticism or to test other people's contributions against my experience and knowledge, such as it is. No one has a mortgage on Nissan/Datsun wisdom, and the more you look, the more you learn.

Does anyone have the actual dimensions of the primary pipe / pipes off the GX manifold?

My 1200GX is in a Triumph Spitfire and some stoopid #### that did the conversion built up an exhaust pipe themselves from the manifold down - and it has two horrible pipes that meet within 3 inches of connecting to the manifold - the bends are horrible and must be restrictive - it then runs into a 1 3/4" pipe.

What I'd like to know is how far two pipes should be run from the twin outlet on the GX manifold - and what size the two pipes should be before they go into a collector.

A picture would make me happier than 6 cups of coffee.

Fantastic input Fellas.
I do like to try and understand the hows & whys of the workings.
Should be more of this , much better than those silly bickerings that go on occasionally.
"GO Datsun1200.com"

89mm
Huzzah, someone i can talk with, & i thank you for your informed response.

You are correct when you state that the cooling effect of the pressure drop across the throttle plate is not great in itself, but it is a great contributor to the latent heat part by allowing the fuel to readily convert to a gas. Most of my driving was, & to a degree still is, long distance cruising & i always tried to lift the vacuum guage needle to as near as possible to 18" of Hg [or more] which is what all good vacuum guages should be reading in. This level of vacuum in highway cruise mode is VERY efficient at converting liquid fuel to gas. I have had the butterflies freeze in my Datsun one cold winters morning when driving to work in Goulburn. The shafts froze in the carb housings, as it was running real good, but wouldn't slow down when i lifted the foot. Natural cruise control. The carbs didnt receive heated air, but the manifold is heated. These throttle shafts are downstream of the variable venturi & are in the fuel stream, so ice built up on the outside of the carb housing, freezing the shafts.

The hot spot system usually works really well when it is in servicable condition with a fully functional thermo & pressure operated flapper valve. By the time the engine has enough miles on it to have a heavy carbon buildup under the hot spot, it is usually well into it's service life & burning a little oil, which is often the source of the carbon, & the flapper valve is usually stuck, often in the part open position. This means that the hot spot is getting at least some, & possibly a lot, of the exhaust flow ALL THE TIME, so it is not innefective, it is often overeffective. Combine this with the aforementioned part-worn engine with low [ish] vacuum & like you said, no problem. If the hot spot was innefective, one would usually know about it pretty soon in a low milage car.

Untill the advent of heated air intakes [flex hose fron air filter to the exhaust manifold] in cars in the late 70's, the easiest problem to fix for the night time NRMA men around here in winter was carburettor ice. The better the state of tune of the engine, the worse the problem. The fix? There was no fix, by the time he got there, the carb had soaked up some heat, the ice in the air passages of the carb had melted, the engine usually started straight up & the driver often left feeling sheepish.

I am the former Telecom Fleet manager for an area that finally extended from Cambelltown to the other side of the Vic border & out west to Young, I ran both the Canberra workshop as well as the Goulburn one & maintained about 600 fleet units of all types. I remember driving my Valiant six [company car] for about a year [1981] with extractors after the exhaust manifold broke. I had it dyno tuned to perfection & the further i drove it in cruise mode, the worse it got. I eventually refitted a new exhaust manifold & it was perfect after that, so from that experience [& others] my observations are diametricaly opposed to yours in point 3. The better the state of tune, the bigger the problem due to the higher vacuum in well tuned engines.

As i had writen before, you are right in your assessment about cold, dense air providing more oxygen, which can burn more fuel, but it needs high gas velocitys to maintain fuel mix stability & usually richer mixtures to compensate for the fuel not converted to gas on the way from carb to combustion chamber.
Now tell me, if you need all this cold air induction with high flow carbs etc to keep up with modern traffic, where are you driving? Taladega Speedway? [NASCAR]... [infantile chuckle ]
I just drove from here to the other side of Taree,... & back,... on Friday, in my near stock 200B, & i kept up OK. Got great mileage & gave the finger to 7 roadside radar Nazi's on the trip.
I think, like you, that the best place for the best torque figure to be, is where you need it most, usually at the engine speed used when passing & for me, that is a lot closer to 3,000rpm than the stocker ever was.

Anyway, what i have learned after more than 35 years in the game, after building & running a variety of hotties, & making the odd error or two, is that factory engineers are not stupid & that if it was possible to make a car that didn't have this feature or that feature [like t/stats & heated intakes] & still have these cars perform to specs, then these things would not exist. The trick is to try to fully understand why a certain design element exists, what benefits it provided & what it blocks, then honestly asess wether changing it will provide a real benefit to you in YOUR APPLICATION, for your driving regime. The stock 1200GX setup served my purposes perfectly, but some of my mates had Datsuns with 45 DCOE Webbers that went faster than my car, but none ever went as well, or for as long. Think twice [even thrice] act once.

Dif'rent strokes.......

GX RULES [does that sound provocative, do you think?]
Chris
P.S.
GX exhaust manifolds are real good too.

Therein lie the strengths of 1200.com

Hey Dodgeman!
There's a couple of details that you may have overlooked.
(1) The pressure drop across the butterfly in a carb is measured in Pascals or when I was a stude, inches of water gauge. This is hardly enough to have any material effect on the heat dragged in in the process of isothermal (adiabatic) expansion. No way! (Hint: look at the very small orders of energy involved- please don't be offended when I suggest that you dust off your copy of Wrangham's "Heat Engines" or equivalent and refresh your memory, because some of what you say is pretty woolly from a scientific viewpoint)
(2) I can still remember when cars had a "hot spot", utterly ineffective after a short time because of the insulating effect of the gas carbon that clogged it up, OR had no manifold heating at all. My recollection is that these cars ran well and delivered their power smoothly without flat spots etc. The only time that fuel vaporisation was a problem was on days of extreme temperature and it boiled (=vaporised in the carb or upstream of the petrol pump). It seems to me that the principle reason for manifold heating is to provide the replacement heat for the fuels latent heat of evaporation. Given that all modern U/L fuels are a cocktail of pretty horrible ingredients (MTBE being a contributor), to get them to be effective (i.e. small enough droplets) probably requires rather more heat than in the past.
(3) Having driven cars with and without manifold heating, I can say
that if the carb(s) and ignition system are tuned correctly there is no particular problem.
(4) You don't have to be defensive about your driving habits, to each his own. Me, I like my car to have the acceleration, handling and stopping to cope with modern traffic conditions where mid range torque is the parameter that counts.
(5) Also, no apology is required for diverting the thread. What is most important is the interchange of ideas and experience that this Club thrives on. To be able to express an opinion, have it praised or criticised without taking offence is the most important thing. That way, we all benefit ;-