Fuel Dispersion, 250 2V Aussie, and 4V carb discussion ?s

[xctasy]

CobraSix, addo, you guys are both on to something.

CobraSix

Maybe I've missed something, but even with dual 2Vs on a log head, that is still a mechanical linkage between the two, with no demand oriented response, only gas pedal operated.

After Running an Offy, I can say that set up kind of sucks sometimes, though once it kicks in teh car recovers, it is great.

and addo said

But generally speaking, the performance progression was 1 barrel Strommie to 2 barrel WW to Holley 350 to triples. These days, only the latter two options get much airtime

That's why I think there is a solution, ex Chrylser, of course. The triple#2300 Holleys the Six Pack 340's had were a superb set up, very like Cliffords, but they just used the single 2-bbl most of the time, and vacuum operated the front and back 2-bbl under load. This is basically a 6-bbl carb with 4-bbl secondaries. With this set up, the Mopar boys had no issues with extra cable load, as there was none! If the Aussie Charger got one of these, no Ford Falcon GTHO 351 would have ever taken it on!

The use of multiple mechanical secondaries isn't a good idea. Lamborghini found out that if all the carbs were synchronus, the throttle travel could be increased, and more mechanical advantage and control, could be used. Chrysler Australia, Holden, and Datsun brought into this. That's what you notice about the best triple carb set-ups, a long travel, almost scary, pedal movement with excellent progression. The early 3929cc Lamboghinis had the same feature, a wild, long travel pedal. My cousin cruised in a Esapada once, and he said the throttle was like a gang plank to the Lord High Executioner... slam it all the way down, and 350 horses ready to draw hang and quarter!

I can put a 2300 Holley any where on a cross flow intake. If the centre branch is used, and two plates welded on the ends, you could fit three 350 cfm carbs. If each outer had the vacuum diaphragm housing placed so it was not hitting the rocker cover, then you could run the whole thing like my Falcon is now. A small 2-bbl flowing through small channels, given excellent torque, and then two bad brothers hanging off the flanks, ready to add another 4.43 sq inches of venturi area to the original 2.215 squares. That's 6.645 squares, and on a 250 cross-flow or even a 250 Log or 2v, thats perfect for the ultimate in performance, for the minimum in cost.

addo's colortune, or my platinum resitance bridge will show perfect mixture distribution if its calibrated right. Exhast gas temperature will be as good as a set of triple Webers of HD8 2" SU's at wide open throttle. There is the potential for 744 cfm with this set up at Wide Open Throttle, and only 248 cfm at the point the auxhilaries kick in. Whats even better, if the engine can't suck enough air, the auxhilaries don't need to open right up, just like a set of triple 2" SU's on an engine too small to take all it's got.

And no extra weight on the throttle, CobraSix.

 

[CobraSix]

I'm not arguing that the 3x1V carb is generally going to be a better set up then any single carb (4V,2V, 1V). I'm still working on my Offy...I haven'te given up yet. I'm working on a Vacuum operated system for the Offy, and maybe at some point I go back to it.

THe only reason I'm changing to a Aussie 250 2V is for simplicity, I drive my car 80-100 miles a day from May until November...and also eventually the idea of adding a supercharger (a year or so down the road). Adding forced air to a Offy would be interesting at best, nightmarish at worse.

Slade

 

[Anonymous]

Just to add another fly to the ointment, try this on for size.

I saw a Triumph TR-6 once with a 3 Weber side-draft set-up on an I6.. They were either 40's or 45's. One venturi per cylinder. Rather scary looking. Granted, the car was set up for club racing, and you could smell the abundant un-burned fuel at idle. I got a ride in it and it was fast. Never drove it, so I can't speak to throttle response.

And, rumor has it, the head was like our I6's- a log head affair. Stress on the word was.
8)
--mikey

 

[Anonymous]

I must say, after all these comments I like the Idea of a two barrel carb that will flow more cfms up too around 400, 450 or 500 literal cfms (not like a 500 holley at 350cfm. This would be as an option for people who dont want to go the four barrel route or to triples.
I know I would use one myself a bit further down the track if it were easily available.
Perhaps someone can come up with a way to get one to be modified to do it. Until then over 220 hp "needs" a four barrel or triples. Or maybe a big bore two barrel will not work that well?
The discussions in the above would be great in the HardcoreTech section.
Regards Tim

 

[addo]

Tim, I think for a large two barrel carb, the venturi design (cross-section) would become even more critical. This is probably the kind of thing which designed the secondary on the Varajet and similar carbs. It may ultimately prove to "twitchy" to be streetable.

Odd point: The 188 Argentinian Falcons can run a single downdraught Weber 45mm set (for amazing strip times), but I have seen very poor results with a similar carb on a 202. It must then reflect manifold design.

So, we then realise that all this talk of carbs, venturis and whatnot sits on top of a manifold that may well be bettered with current needs taken in hand. A pair of manifolds for a 2V, each running a progressive carb, would be interesting fodder.

Adam.

 

[xctasy]

Ah Addo, the Offy Dual Plane 2V/4V intake mit twin Weber/Holleys.

Theres an idea!