1000coupe - I was talking tri-ys on v8s where eac 'side' has 4>2>1 (which is 3 Ys - 1 for each of the primaries to secondary pipe, then a final one (per side) from the secondary to the main collector. I wasn't suggesting they are popular on 4s, just aiming at a quick once over as far as why they exist at all. There are indeed tri-ys for 6s - 6 into 2 into 1 - but I'd suggest they are done to make for less total piping/space taken up, 6>1 still work better.Sorry if my post is confusing - I'm far from an expert, but my biggest drama is I tend to understand stuff a little bit better than I can effectively/clearly discuss it!

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opkey dokes - in that one the final pipe out of the collector might be tucked inside the 4-1 flange. Here is a pic (it was done for another forum some time back so please ignore the fact there are only 3 primaries - it was done to show an inline 6 with 6-2-1 pipes. The 'blue' area shows where it would trap heaps of exhaust flow. On some I've had (one for a hemi 6 in fact) the final pipe tucked a good 1.5 inches inside the flange, making a big obstruction to flow. In your example, nobody could say without cutting it off. If you cut carefully around the weld you could pop the pipe out without cutting all the way through, then flare that same pipe and re-attatch.




The second picture is as referenced in the first post - at the top is a 'typical' extractor - where the flange obstructs the port exit ever so slightly. The second is 'port matched' which is good, but the bottom one is opened a touch further to create an anti-reversion step (if the exhaust tried to go back in the port, it'd hit that step/edge and less would get in there). The green on that final picture is to show that in some cases, you might have to add weld (mig is good if you have access, I've actually done it by oxy a couple of times, because that is what I had) on the outside meeting point of flange and primary pipe.




Last thing I'll show - is photos of some extractors a mate got for a hemi 6. The port 'holes' in the flanges weren't cut straight - so when it looked 'lined up' on the outside, it wasn't on the ports. In the worst case, it blocked more than 1/4 of the port on the worst one. That had to be welded up to buggery to get it to line up - I had to actually add steel to the flange because I had to grind out past the end of the flange to line them up!! On which note, they were coated (they weren't manufactured by) jet-hot - a great coating. but since they had to be modified, that coating had to go for the welding to be done. I'd _strongly_ suggest sourcing extractors as is, then ensuring they fit optimally (or making them do so) and then and only then get them coated if you wish to.













The extractors were fitted originally at an exhaust place, and when it started to leak, we took them off to look, and you can see by the carbon deposits how far off they were. In the last pics, you can see that the entire left wall of the flange is actually new material. Given the amount I had to add to them, I thought for sure they wouldn't last, but they ended up on the car for a fair amount of time (approx 12 months) and didn't crack (he ended up upgrading to new pipes with larger primaries anyway)


The only other thing that comes to mind - Although I discussed the rpm sweet spot of headers vs their primary pipe diameter, it should be noted that pretty much _any_ extractors (the aforementioned issues notwithstanding) will provide a power boost - simply because they (combined with a freer flowing exhaust from there back) reduce exhaust backpressure vs the factory cast iron style stock (the GX ones, that I've only seen pics of, are likely a different story) and less heat under the carb - all of which boost power. What it's about however, is getting hold of all the potential gains - the drop in backpressure/heat _as well as_ the gains from optimal pipe sizing.

all things being equal, 4 into 1 headers are 'the go' the reason tri-y types work well on V8s is due to some other V8 specific shenanigans (due to a 90 degree crank phasing and uneven firing of each bank).

Generally you need to look at those which have enough meat around the flanges so you can open them up so they are about 1mm larger than the exhaust port exit. If they are smaller, it's a blockage to flow. If they are a mm bigger, it creates an anti-reversion step (pics on request) and helps extend the lower rpm range of the extractors with no loss up top. Similarly, where any joints are - mostly the collector on 4 into 1s - it's important that the next pipe along is flared and slips 'over' the pipe it connects to. On cheaper ones they slide the pipe inside and weld around, and on the inside, where the exhaust flows, it's like a big air dam/parachute and rules out 90% of the effects.

Beyond those issues, which are mostly those workmanship rather than application specific (i.e. they apply to all extractors) the next thing is a fairly well known about 'science' . Basically if you know the capacity of each cylinder, and the rpm range you intend to run it in (in your case the racing rpm range, with little thought for anything below it relatively speaking) there's a formula for working out ideal primary pipe diameters. Conversely, if you know the pipe diameter, and cylinder capacity (easy enough) you can work back and determine what rpm range they will work in. Of course pipe _length_ does influence the powerband, but it's _very_ mild compared to pipe diameter. People harp about equal length primaries - and that's all well and good - as long as they are all equally the 'right' length. In practice, since the length isn't the big influence it's made out to be, a couple of inches difference from pipe to pipe is nothing to lose sleep over.

The 'formula' is based on the fact racers over the decades (well before I was born) noticed that if the average (not peak) exhaust gas speed was up around a certain speed (and I bloody forget exactly what that was) it'd produce the biggest lift in torque at the rpm where that happened . So based on a cylinder volume, if it's spinning at a certain rpm, and has to push all the exhaust through a cross section area of a known size, you can work out the gas speed.

Rather than go through all the stuff, here's the formula (and note it's based on pipe INNER DIAMETER - and most extractors are listed by pipe OUTER diameter. I usually just take 1/8th of an inch off the id and am done with it.


R= rpm
P = primary pipe area in sq inches
C = capacity of one cylinder in cubic inches

R = (P x 88200) / C

TO get the primary pipe area simply divide the id by 2 then multiply that by half the id, then by pi - 3.14159

i.e. (id/2) x(id/2) x 3.14159

If you need to calculate the cylinder capacity, there's a small calculator called engsize.exe or similar on http://billzilla.org

And for converting cubic inches to cc or vice versa do a google search for 'convert.exe' a brilliant freeware program.

Let's do an example :]

A 1200 engine (which is technically what - 1171cc??)

a12 - 1171cc or 292.85 per cylinder or 17.8708 ci


and we have extractors with a 1 3/8 od or 1 1/4" i.d. (approx)

1.25/2 = 0.625

so 0.625 x 0.625 x 3.14159 = 1.22718359375 -

I round that down to 1.227

So the pipe cross section is 1.227 sq inches and the cylinders are 17.8708 ci


R = (P x 88200) / C
R = (1.227 x 88200) / 17.8708
R = 108221.4 / 17.8708
R = 6055rpm

So what that means is that for a std bore 1200 motor, 1 3/8 OD primaries provide the strongest torque boost at 6055rpm. That doesn't necessarily mean that the torque peak will be 6055rpm - not at all - just that these extractors will be in _their_ sweet spot at 6055rpm. In practice, they happen to function very well a good 1500rpm either side of that, often as much as 2000rpm either side of it.

If we did the same on a 1500cc engine, it'd be more like 4750rpm for the same exact extractors.

As for collector sizing, it's more down to experience. On a 1.2 you'd be looking around 2 inches, and probably 2.25 on a 1.5litre for most apps though you'd tweak it either way depending.On primary length, it'd depend heavily on cam choice etc, but you'd not be hurting with up above 32-34 inches on a 1200 (which is in all probability far longer than any off the shelf unit would actually have.

If you can discuss the combo a little more, a more specific answer could be given. I've taken the stance that it's better to talk about the dimensions/design you'd most want rather than brands, as believe it or not, amongst different brands, their headers for some engines are really excellent and for other engines are woeful.

The above math has been refined above and beyond what I've outlined above. There is software that can calculate it down to the half inch for lengths with no sweat. I don't actually have it, but know someone who does, and I reckon they'd be willing to plug the numbers in if I emailed them about it, if you like.

1800kms round trip (outside Melbourne to Western Sydney and back) in a 1200 coupe to pick up an a15 motor. On the way up it was 40 deg C outside and the motor started running hot so I had the heater on to take some heat out of hte cooling system. Stopped once for fuel and once for food each way, and about a 10 minute break after getting the motor in the boot (bad idea by the way, poor fit through boot lid area)

The drive home was mostly at night, and a hell of a lot easier. Only cost $110 for fuel all up (so around 110 litres for 1800km, and I wasn't exactly driving economically.

One big difference between Victoria and NSW - there are warning signs before speed cameras in NSW, and more to the point, they seem to be in 'reasonable' spots. In Vic if they ever put one near or at an accident blackspot, it'd be purely coincidental. all about revenue down here (and for hte record, I didn't break the law during the drive though I didn't muck about either)

If I had to do it again, I'd not do it before replacing the seat (not enough leg room for me in std form) and possibly a smaller steering wheel for the same reasons.

The motor ran smooth as silk (original factory a12 still going strong since 73!!) there and back, a little warm in the middle of the day, but didn't use water, and isn't using any water or oil back in melbourne! I do think that I could have done it easier with a freer flowing exhaust (1 inch outlet is probably a little restrictive even at highway speeds/throttle inputs.

Don't connect the fuel pressure regulator boost reference line to the inlet manifold if it's a blowthrough! If you do, the vacuum at part throttle will drop fuel pressure possibly to the point you don't fill the fuel bowl at part throttle!

The other reason is that as air passes through the carb, through the venturi, it drops 1-2psi under boost conditions (and about 1.5in Hg under atmo non turbo apps, more for some older oem carb setups, and less like around 0.75in Hg for properly optimised competition engines). You _want_ it from befor the carb mouth, that way under boost you have 1-2psi more fuel pressure, which acts as extra insurance under boost. As soon as you go 'off' boost the pressure in the plumbing from turbo/supercharger outlet to carb mouth will not go above atmo, so it stiill runs the same off boost, and won't flood (as long as the supercharger has a bypass for part throttle, which I mentioned in the other thread about fuel pressure)..

For the boost pressure _guage_ I'd actually make a _very_ strong case for plumbing two fittings - 1 to somewhere between turbo/supercharger outlet and carb mouth, and the other to the inlet manifold. Then you can (once it's all setup) look at the boost pressure before and after the carb mouth. The boost pressure in the inlet is the 'true' boost pressure in all fairness, and representative of what you might expect as far as output. Recording that boost level across the rpm range, then switch the guage to the fitting before the carb mouth. This will (due to the venturi causing a pressure drop, which it needs to to meter fuel at all) show a higher pressure.

You should expect 2psi or so higher reading before the carb vs inlet manifold - pretty much no big deal. BUT if the pressure difference is 3-5psi (let alone if it's more than 5psi) then it's clear cut evidence that the carb is too small and acting as a restriction. This is bad on multiple fronts - 1, it's restricting how much air/fuel can get in there for any given pressure before the carb so overall less cylinder filling, and less power. 2. if the blower or turbo has to work harder to get the air/fuel in there it will cost more power (either at the crank to drive the blower, or through pumping losses of the pistons pushing against the turbine and it requiring more work to achieve the boost) 3. Since it's working harder, apart from pumping/mechanical losses, it's also going to heat the charge up more which means it's closer to detonation, and at higher temp less dense, so less power yet again.

Having the two boost guage takeoff points where you alternate plugging one off and running the other to the guage(heck even going as far as to run two gauges) can tell you a lot about the suitability of the carb, and whether you could have the cake and eat it too - and end up with better cylinder filling with less chance of detonation via carb size optimisation.

It's gotta track with boost. so it's always 2-3psi + boost pressure to be safe. Holleys in general can handle as much as 7-8psi static without trouble, so 7-8+boost pressure is the go. Other carbs - most of the sidedraughts and most downdraught webers will _not_ cope with that - 2.5-3.5psi should be about it - i.e. 2.5-3.5psi plus boost pressure. The reason for that is that above 3.5psi many of them aren't able to successfully close the needle and seat (it's basically due to the leverage of the float/link arm and how it acts on the needle and seat) - so it will over run the needle and seat and flood the carb as the fuel bowl overfills.

Another thing you'll find with most sidedraughts and downdraught webers (to a less extent) is that they'll tend to lean out under boost (even with adequate fuel pressure) - due to the way their fuel and air corrector/bleed/emulsion circuits work. you _can_ definitely work around this and get the fuelling right under boost, but they (at least sometimes) then are 'off' the optimal a/f curve when off boost.

There is a simple way around this - you run a restrictor ring at the mouth of the carb. It has to be just a few mm smaller than the mouth of the carb (still likely larger than the venturi/chokes for the webers) . for whatever reason, this allows the emulsion circuits etc work a lot better. It basically doesn't affect them much at all for normal driving, but once more rpm and boost is on board, and flow starts to really increase this restrictor ring will cause slightly less pressure through the mouth of the carb, which pushes more air pressure (relatively) to the fuel bowl, which then automatically enrichens (above and beyond the carb circuits ability from beforehand) under higher boost/flow.

Such a phenomenon isn't a big secret. If you lok at the mg metro turbo setup (basically a mini engined car that looked like a ford laser, which ended up with a turbo to account for hte fact it was in a larger car than a mini, and had a mini (i..e 1959 tech) engine powering it. The carb 'hat' or plenum has a sleeve inside it that works as a restrictor ring. Take it out, and it'll technically flow a little more, but fuelling under boost is way way way off, and generally not recoverable. Similarly, there was a turbo kit available (again for the mini) from Janspeed that used a dellorto (as far as I can remember) in a blowthrough setup. It too ran a restrictor - in the shape of two rings placed at the carb mouth.

Yet further on minis, a long time contributer to the mini-list mailing list had an mg metro turbo setup in a mini, then went to a dellorto,

found it on google

and tried extensively to get around the restrictor ring option, but nothing worked (and he tried all emulsion tubes and air correctors etc under the sun). There was a fair bit more detail on this on the min-list and the old blowthruturbol list at the time than is on the website but the main important stuff is there.

This _is_ a lesser issue on the smaller dgv style webers (pretty much all downdraughts save for the ida/idf stuff)

I'm adding all this because even _if_ you get the fuel pressure/supply into the carb right, you might still run into issues of it leaning out, or being right for boost but terrible off boost. If you manage to source some of the webers that had been used in factory blowthrough (and the carb hat if they had them) it'd be a better start.

With a holley 2 barrel, you can address the phenomenon almost solely by going to high speed air bleeds that are around 1/2 the area (area not diameter) of std for that particular carb

Only other thing to remember - on some oddball carbs - under boost in a blowthrough for fuel to flow you need to route full boost (from before th carb mouth) to the fuel bowls. This usually isn't a problem at all, because the fuel bowl vent is routed into the carb main body well inside the air cleaner base attachment point, so it automatically gets full pressure. then air travels through the carb, through hte venturi, and it sees a slight pressure drop (so let's say you have 14psi boost pre carb, by the time it goes through the venturi it might be about 12psi - so there's a 2psi difference between air above the fuel in the fuel bowl and the fuel introduction point in the carb throat, and fuel will flow. On those oddball carbs where the fuel bowl vent is to somewhere else, as soon as you get boost in the carb throat, there's none above the fuel in the fuel bowl, so no fuel will flow (in fact air will be pushed backward through the fuel circuit and into the bowl through the jets etc.) That's one of the 'sneaky' reasons the engine can die flat on its face when you get any boost pressure, even though fuel supply/pressure is perfectly adequate.

Lastly - on a supercharged blowthrough, when you close the the throttle or even at part throttle, the charger is trying to push heaps of air through there but the throttle won't let it - as a resuly you get stuff all pressure (or partial vacuum) in the inlet manifold but possibly 10-20psi or even more above the throttle plates. Apart from causing more heat, and possibly blowing a hose, it'll put massive air pressure above the fuel in the fuel bowl and push significant amounts of fuel through the idle and transition circuit and cause flooding/stall soon enough. In that scenario you need to have a bypass valve plumbed in there so that at part throttle there is somewhere to dump excess air from the supercharger when it's still sspining and the negine is at part throttle. On a blowthrough turbo, you can usually get away with it, as it only spikes a little when you lift off after a full boost run. The turbo soon enough spools down and the pressure pre throttle drops back to atmospheric, and it's 'all good' . you can get these bypass valves through places that stock stuff like 'pro-chargers' which are made for blowthrough carb, or you can diy one, or you can even rig up a turbo sourced blowoff valve.

I'm just trying to cover all possible bases as far as things that might still be playing a part and might make it 'appear' that something else is wrong or that some other change wasn't also warranted.

a14 head on ebay

This one is for sale, and in Melbourne. Let me know if you are going to bid on it, otherwise I'll grab it for myself (or try to). I don't 'need' it but if nobody else wants it a spare would be good. I'm just hoping to avoid bidding against a fellow forum member and putting the price sky high only to eventually pull out of the bidding or something.

Since this one has sold, would it be possible to get details of where/whom it was purchased from? Perhaps a part number/reference?

Is the motor still std bore, or has it gone oversize, and if so, how far??

Most of the answers would be 'it depends' - if you want to do it properly and safe (which is the only way worth talkin about - no kidding!) - allright - to raise you'll need new springs at the front, and be prepared it will alter wheel alignment and likely in a bad way (wearing out the outside shoulder of the front tyre treads would be my bet).

If it's leaf sprung rear, you can get the leaves re-set, and possibly add one more leaf to the pack (whiich will make the rear end twitchier, esp in the wet, as will raising it, so you have a double whammy of danger). That'll only give you a couple of inches before you start running into trouble with shocks reaching the end of their extension.

Lowering it, you 'could' cut the front springs (but I _absolutely_ don't recommend that) - which will drop it a good couple of inches, and also make for a much higher spring rate (since hte softness or hardness of a spring in terms of how to compress it is a combination of how thick the spring coil material is, and how many coils or loops are in there it'll start lower and likely bottom out easier, but the actual spring rate itself would be higher. Worse still, if you cut too far, when you jack up the car, the spring might not extend long enough to stay in place, and can flop around. this could come out or jam/skew if the wheels come off the ground on rough road or if you go airborne over a crest, and if that happens, when you 'land' you'll almost certainly veer uncontrollably off the road and or into something.

On the back you can use lowering blocks or re-set springs. Be aware that if you lower it to the point that the axle centreline is higher than the front spring eyehole (or roughly the front lowercontrol arm bush centreline on 4 link rear ends - roughly - I won't complicate this with the full mate/points of intersection etc) then when you accelerate it tries to unload the weight on the drive wheels and can lead to wheel hop and general instability under full throttle (esp coming out of a turn).

In other words, generally going more that a couple of inches higher or lower than stock is a bad idea (and I haven't even mentioned the damage that can be done bottoming out shockers/suspension components when too low.

Generally the accepted minimum lowest is that an object that is 4 inches or 10cm high should be able to be driven over (obviously not by the wheels/tyres) and nothing on the car should hit it. A coke can is about that measurement, so that sounds pretty much on the money. A lot of trolley jacks aren't far off that either, so if they don't fit it's also a giveaway.

Some of the above sounds like 'the sky is falling in' and it's not meant to be, it's just a (very brief and simplified) overview of some of the risks - and it's important to get them 'out there' because whilst you'll get good advice here and a few other forums, you'll find no shortage of idiots elsewhere who will just blindly say 'cut the springs' without even knowing about the fact that they might drop out (some don't mind you, but you have to check or find someone else who has done it to the exact same model and know for sure) - the same tools who would say 'it's all good bro' will be nowhere to be found if their advice ends up hospitalising you or someone else :)

on some circuit race engine sumps, they have tubes, with a smaller tube that has a tapered seat ground into it pressed inside, then a ball bearing (a couple mm smaller than the i.d. of the outer tube, but big enough to seal off the inner one) and a split pin to stop it rolling all the way out. If you put one at the bottom of each baffle, the ball rolls and closes the 'outside' axle during cornering, preventing oil getting past, and the other one is open, allowing any oil on the 'inner' side to get back to the centre. At rest and in a straight line, due to the ball being a few mm smaller, it also rolls away from the inner tube and lets oil drain back quickly. This might work even better than angles or fixed holes, but it's a question of whether there is enough room to fit them or whether or not the baffles don't already do more than enough.

I'd actually make a case for their use on circuit racers, as with very few exceptions you'll always be doing more corners turning one way than the other, so without flaps or one way valves, there's more likelihood of a bias in more oil getting past and remaining on one side (*the mostly outside for that circuit) axle tube region.