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

[CobraSix]

This was starting on the end of the Offy 3bbl post, so I figured I'd move it out for discussion as it's own topic. Better for searching and responses that way.

First...here is where we are. We got off of the Offy topic and on to the Aussie 250 2V that ws converted to 4V. Debate started about which way to better mount the 4V. One person has theirs mounted with the primaries perpendicular to the engine (primaries are on the front part of the intake) and another has the carb mounted perpendicular to the engine such that the primaries are parallel to the engine.

School of thought for the second set up is more even distribution of fuel for the fore and aft cylinders. I think the downside of this is possible problems with fuel flow through the venturis, especially under heave acceleration.

If you do the first set up, then the forward cylinders may have a minutely better fuel mix (or richer at least) while the primaries are in use.

Then the question came up of plenum height (adding a spacer). Plenum height will make a difference in power. It is two fold.
1) The fuel/air mix is allowed to cool slightly allowing more power. I think this is slight.
2) Gives a more ready reserve of fuel/air read to move to the next cylinder instead of waiting to be drawn through the carb. It also allows better mixing of the fuel and air.

So...any thoughts, comments, questions...let's start.

Slade

 

[Anlushac11]

8)

My 250-2v manifold was setup so the carb runs parallel to the valve cover. I was also worried about fuel distribution. My answer was to buy a 1" spacer. I thought that would give the air-fuel mix more time to fill the plenum. I am still worried about the distribution but feel this will minimize the effects.

 

[Anonymous]

Mustangroo told me that Jason, his son, doesn't use the space anymore and Jason gets gut busting torque.

A problem that I've heard when the carb is mounted perpendicular to the motor is fuel starvation during hard cornering.

I tend to worry about my straight line perform, the Comet can't/won't ever see any sideways action during turns.

db

 

[Anlushac11]

Mustangroo told me that Jason, his son, doesn't use the space anymore and Jason gets gut busting torque.

A problem that I've heard when the carb is mounted perpendicular to the motor is fuel starvation during hard cornering.

I tend to worry about my straight line perform, the Comet can't/won't ever see any sideways action during turns.

db

Are you talking about the floats sticking during cornering? that can be cured by switching to a Holley center pivot float.

My Mustang is being built for a Auto-X and road racing suspension. I want handling as much if not more so. And the low end grunt of the 200 combined with a T5 and 3.73:1 Traction Lock rear will help greatly. I think will help accelerate out of corners.

 

[Anonymous]

Traction Lock rear will help greatly. I think will help accelerate out of corners.

I hear that a Torsen is the way to go on a road-racer. It will always give more torque to the tire with more traction (generally the outside tire in a turn). Helps back end steer around corners. So I hear. No practical experience...yet. You'd need an 8.8 or 9" to get one, though.

Changing topics yet again- who you going with for performance suspension components? I'm looking to go the same route with mine in terms of handling. Probably a little tamer since this also needs to be a daily driver.

Sorry guys. How do I move this out to a new topic so we don't walk off topic yet again?

--mikey

 

[Anonymous]

Are you talking about the floats sticking during cornering? that can be cured by switching to a Holley center pivot float.

This fuel starvation topic was discussed several months ago, I think the general consensus was to convert to Holley center pivot float like you mentioned. So I guess that's the solution to the Holley being off kilter.

In my case, I'm using an SP head which has the two inlet holes parallel to the head. IF I were to stick with a 4bbl carb setup I would've had to convert the float. My other option is to use a throttle body off of an LTD which would mount perfectly with a redline carb adapter. So EFI SP 250 w/T04 turbo.

db

 

[Anonymous]

It would seem to me that turning the carb so the primaries are parallel to the engine would be better for fuel distribution...

My only thoughts would be running the throttle linkage and the above mentioned changes in the relationship of the float and fuel bowls... the center hung float would be the ticket for that....

 

[xctasy]

Primaires should sit in clse to the stock position, the secondaries where ever. I wouldn't turn it around, I'd stick with it the way any Holley should sit.

With a dremel or die grinder, I'd take the first two inches off the dividing stakes.

The intake volume is massive with any 2V intake. I'd say any spacer would push the carby up too high to fit under a Stangs bonnet, even with the lo-deck 200 block. If it ran a big lift, short duration cam, a one -inch spacer would help.

The linkage is the issue. On OHC Ponchos, the 4165 , 4175 Holley or R'chester 4M 4-bbls were hooked up end on as per DBzOkoles, but they had an open plenumb to non-dived intke ports.

Heck, the only 4V sixes I've seen in the flesh were orignially 2-bbls, with a large one inch ramp adaptor which allowed the primaries or secondaries to discharge there fare, not both. Very similar to the Mustang II 2800, Capri 2600/2800 and Pinto V6 2.8 adaptor used for the Holley Weber 2-bbl. That way the plenumb area is kept back to the stock 2V intake, not enlarged any.

 

[Anlushac11]

8)

My intake which was modified back in Oz for a 4bbl has no center divider. Its just one big open plenum chamber.

 

[addo]

Time to play contrary bugger again. If a 4 barrel carb is such a good thing with a 2V, why did noone ever make a manifold for it? You could get Weber, Dell'orto and SU manifolds.

Not dismissing the concept of 4 barrels, but ideas like Al suggested with two progressive carbs will likely run even better.

As I brought up before, running a "colortune" plug will confirm or deny the positive effect of one big 4-pot carby, especially in regards to evenness of fuelling. I am not going head to head particularly with anyone, but if this was a dead-set ideal combo, wouldn't it have been used here (Oz) along the way?

Just some things to consider.

Adam.

 

[xctasy]

Of course you are right, Adam. And you're not Devils Advocate, bro', its common sense!

It's just that there are no BMW 3.0S-style intakes for this engine. The real crime, is that there are no DGAS 32/36 Triple Weber carb intakes for the 2V. When a 250 sucks about 83 cubes per pair of intake tracts, and Eurpoean/Kiwi/British Pinto 1.6 liter OHC engines had a single DGAS 32/36 feeding an 88 hp basemodel, then we deserve to have 264 hp for our 250 2V's at the very least.

I think that one 4-bbl carby per engine is silly, but the cost of the other options, and the cost of the intake are the fly in the ontment.

Get this. One 600 cfm Holley 4-bbl has 5.16" of carby venturi, 2.454 open on the primaries, and an extra 2.706 on the secondaries

19|#4150/60|600|4-bbl-|1.5625--|1.25000--|2.4540|25.0-|1.5625-|1.3125-|5.1600-|~279ft/sec|183|375|

Three 32/36's, 2.547" on the primaries, and 2.661" on the secondaries

04|#5200-|280-|2-bbl|1.2800-|1.0400|0.849â€￾---|23.1-----|1.4375-|1.0625----|1.736“-----|387FT/sec|061bhp|124bhp|

The triple carbs have a much smaller wetted perimeter and time of concentration for each drop of atomised mix to cover. The 4-bbl disrtibution is plainly much worse, with the outer cylinders 6 and 1 starved, and 3 and 4 over supplied.

There is no difference in carb venturi area overall. Both have ~372-375 hp of carburation, and 183 hp on the primaries if the seocndaries were closed.

Tick to the triples for distribution!

Al's case is just as relevant. Comparing a 390 cfm carb to twin 32/36'S, the same deal.

11|#4150/60|390|4-bbl-|1.4375-|1.0625-|1.7730-|43.7-|1.4375|1.06250-|3.547-|~264ft/sec|122|244|

The outer cylinders 6 and 1 starved, and 3 and 4 over supplied with the 4-bbl, and no problem with the twin carbs.
The 390 cfm flows 244 hp, the twin 32/36 flows 248 hp, with 122 hp on the primaries for both carb arrangements.

The figures don't lie. It's not a stich up.

Were's me bleeding triple carb set up for a 2V? No-were, man!

I'd stick to 4-bbls, and hope for a set of triple SU's or Webers to fall out of the sky if I was into gasoline induction systems.* From http://fordsix.com/forum/viewtopic.php?t=7015&start=0&postdays=0&postorder=asc&highlight=

 

[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.

As far as other manifolds, look at the 300 manifolds. I think they make a 4V and a dual 4V manifolds for the 300 engines.

Sure, a Dual 2V would give better distribution, but at a price.

Slade

 

[Anlushac11]

8)

I dont now about in Oz, but in hte US it seems there is no one my age that tinker with cars that does not have some exposure or experience with a Holley 4bbl. It seems it was a right of automotive passage that you at one point had to tinker with a Holley.

Dont get me wrong I would love to have a 3x1bbl or a TBI setup on my 200.

I think a 3 x Holley 5200 would be a nice setup. Carbs are cheap and plentiful and airflow would not be a problem.

BTW anyone know what a Weber DGV series 38/38 flows?

 

[Asa]

I dont now about in Oz, but in hte US it seems there is no one my age that tinker with cars that does not have some exposure or experience with a Holley 4bbl. It seems it was a right of automotive passage that you at one point had to tinker with a Holley.

does that mean i'm not a gear-head? to the best of my knowlege, i've never touched a Holley while on a car, and actually, other than at swap meets, i don't think i've ever seen one period...

 

[Anlushac11]

I dont now about in Oz, but in hte US it seems there is no one my age that tinker with cars that does not have some exposure or experience with a Holley 4bbl. It seems it was a right of automotive passage that you at one point had to tinker with a Holley.

does that mean i'm not a gear-head? to the best of my knowlege, i've never touched a Holley while on a car, and actually, other than at swap meets, i don't think i've ever seen one period...

Thats right..your sir are a youngin, a whippersnapper.

Dont feel too bad. I run into guys all tha time that make me feel stupid around fuel injection and they freak if they have to touch a carb, they think the p/n will be in hieroglyphics.

 

[Anonymous]

I think that anytime you can spread the charge on the intake runner it will help, doubles and triples (or more ) are going to work the best, but there is the issue with balancing multiple carbs.

Possibly the solution lies in multiple electronically controlled throttle body fuel injection

Not for me though, I'll stick with my Offy for now I'm happy with it

See Ya'
Mike

 

[Anlushac11]

I think that anytime you can spread the charge on the intake runner it will help, doubles and triples (or more ) are going to work the best, but there is the issue with balancing multiple carbs.

Possibly the solution lies in multiple electronically controlled throttle body fuel injection

Not for me though, I'll stick with my Offy for now I'm happy with it

See Ya'
Mike

Im not a electrical expert but I was wondering if you could run 2 TBI's with a Megasquirt using one set of sensors?

 

[xctasy]

You can do lots with TBI set ups, but the air fuel atomisation often is worse than a conventional carb, according to the FrenchTownFlyer.


Oh and to this question,

BTW anyone know what a Weber DGV series 38/38 flows?

Based on the area increase, and the fact that the stock 5200 flows

200 cfm at 1.5"Hg :arrow: 248 cfm
230 cfm at 2.0"Hg :arrow: 286 cfm
280 cfm at 3.0"Hg :arrow: 349 cfm (Holley #2300 flows 350 cfm).

So its almost a 350 Holley. It's an excellent carb, I've heard. It flat lines at 155 hp or so, just like the 350 Holley.

 

[twentyover]

Directed at Cobra Six

One of the beauties of the constant depression carbs used on English cars ( SU and Stromberg CD's) (besides being side-draft) is that the flow area of the car is rpm dependent.

Unlike the offy deal where you slap open the throttle and you mechanically open the end carbs, getting an immediate reduction in flow velocity due to the huge increase in throttle area and a fixed venturi area-

Assume you have a set of constant depression carbs. Outside of the fact they are extremely sad all the time, remember they are on a common throttle shaft. Go full throttle and the butterflies immediately open. What makes these hombres work is that there is a slide and needle in them, and the slide stays in the airflow path, resticting initial flow. As flow increases as the engine picks up, the slide moves clear of the airlow path, until it finally totally clears the area at high throtlle and high rpm. Imagine this as something like a vacuum secondary on a 4 bbl, but it's actually a vacuum primary.

Downside is- they don't accelerate quite as fast as fixed venturi carb. But remember- there alot of stuff you can do to help the engine rev faster- lighter rotating weight ( flywheel).

Find a Datsun 240Z and take a good long look at the carbs. These were built by Hitatchi under license from S. ALL the stuff for these are still available- Z- therapy for the Hitatchi SU and HS6 SU's, and Curto and Hawkshust for the entire range of H, HS, HD, and HIF carbs. Burlen over in England makes all new carbs off original tools for this stuff, so there are no worries about avaialability.

Obviously, i'm a fan of the SU (more so than the Strombergs), butt stomberg parts are also available (tho I'm lead to believe less available than the SU).

Check it out and think about it.

 

[addo]

Note that my opinions of four barrel carbs are tainted by amateurs and garages installing untuned, ill-matched carbs on worn V8s using the "Put a Holley 600 on; that'll fix it" basis. There's no shortage of these dipwits and their motors even today.

As I mentioned, I find it weird that no four barrel carb manifold was produced, if it's such a valid idea. Australia was no stranger to either Holley carbs (on the Falcon GT) or hot sixes. The hottest sixes we put out in the good old days ran triple CD175 for the GM 202 cuber, and the 265 Chrysler ran triple 45mm Webers.

Both these engines have bolt-on manifolds; 4 barrel manifolds are available from a variety of sources. 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, with the possible exception of (2 barrel) Carters on the Mopar sixes.

Check any of the Aussie boards for Toranas or Chargers or Pacers. Note the carbing and capacities.

Cheers, Adam.