Home-brewed IR combo?

[Anonymous]

I have an NOS Holley 2210 2bbl carb, listed as 350 or 380cfm (I forget), never been on anything. These came stock on mid-70s base-model Chrysler Corp 383s and 360s. They had either a single-stage or 2-stage power valve; mine is the former.

I'm wondering whether, if I obtained a second carb to match this one, they could be made to work on a homemade individual-runner set-up for a transverse-mounted four-banger. I.R. set-ups are done all the time with Webers, and Webers are admirably adaptable and tune-able, but they cost a lot, even used, and more than I want to spend on this car, whereas old 2bbl Holleys like this one are giveaways. The 2210 has some slots milled in the bottom of the baseplate. As long as I build the manifold so that those passages are working, will I have a problem with powervalve actuation or any other factor? Would I have to have a little balance tube connecting 1-2 with 3-4?

 

[xctasy]

No problem with power valve operation. You'll just have to change the effective power valve channel restriction (PVCR) size via a brass insert down to 16 thou dia or eliminate it entirely. You can externally reference it like on a #2300 or 4150 series boost referenced Holley using a Does 10s syle mod, or use a fuel control valve. You can then tailor any kind of vac source, poerted, mainfold, even vac pump or whatever.

Stock Holley operation of a power valve has the total fuel delivey in cc/min going up something like 8 jet sizes on stock on a 2-bbl V8. When you go to an independent runner, the carb is duplicated 3 times over, so it then has to get jetted down drastically, and then needs to operate like a Weber DCOE by having an idle, progression, and full throttle calibration. Its like comaring a mono jet Chrylsler K-car thottle body EFI to a multiple point one.

I've not done it yet, but the Power Valve dispersal orifice is the PVCR, so to work on an IR port on port system, it just needs down sizing a huge amount.

For stock 144/170/188/200/221/250 sixes with power peaks in the 4400 to 5500 rpm range , I've used a copy of the Alfa Romeo 1.3/1.6/1.8/2.0/2.3 Weber DCOE jetting. I got it as a desktop program back in 2007. It generally sizes the donar carb venturi at 0.040 sq inches of carb venturi for every Cubic inch displaced. So a 140 cid Alfa Romeo DOHC engine reving to 5500 rpm needs 140*0.040, or 5.6 sq in of venturi area. That then gives jetting to suit. It is a guide that allows you to determine what Holley jet sizes for any given Hp would look like with no power valve at all. You then find the Holley jet call sizes, and then down size them to allow for a 2 stage Holley 2210 power valve actuation so it operates like the idle and progression and power circuit on a DCOE. I'd hazard a guess that the PVCR could just be down sized by trail and error to allow for a rich lean variance. I'd not be using PVCR to equal 8 jet sizes under wide open throttle, I'd drop it back to a third that. 2.5 jet sizes via PVCR under wide open thottle.

 

[Anonymous]

I'm sitting in McDonalds this evening, freeloading on their WiFi hook-up. I just finally found my big Holley book before coming over here, so when my battery runs out, I'll get to studying the book. My recollection of the way the powervalve feeds fuel may be all wrong, so I'll come back when I can talk semi-intelligently. Thanks, Dean.

 

[Anonymous]

(Gawd, this laptop is flaky! Hope I can get this out)

Okay, I'm refering to the book and trying to get what you're telling me. Without having taken the carb apart yet, by the parts blow-up it appears that the power valve discharge channel runs off at an angle just below where the power valve threads into the bottom of the float bowl. Is there a removable orifice there that I should remove and replace? Are you saying to make a brass slug with an .016" hole in it and press the slug into the channel (as a place to start tuning)? And I'm not sure what you mean by "you could externally reference it"? Are you still talking about the PVCR? Also, it appears (?) that the power valve piston is normally actuated by manifold vacuum; why would the other options you mentioned be desireable?

The 2210 came with either single or two-stage power valve, but the 2245, which is almost identical, has a gradient power valve which might retro-fit if that's desirable . . .

Dean, you say that with an IR set-up the carb is "duplicated three times over" (or twice, since I'm talking about a four-cylinder) and therefore has to be jetted down drastically. Why is this? The air-draw is a lot more pulsating when coming from a single cylinder rather than from four cylinders (V-8 with dual plane manifold) and a plenum, and it may be that this carb won't be happy with that pulsating signal. But the venturi is the same and the air/fuel ratio desired is the same, so why jet way down? You can see I've never done an IR intake on a car!

(My other carburetor option is to find a second Weber 40DCNF-12, which is probably the wise route to take, even at the likely extra $400 or so that I expect even a used carb to cost me.)

I'm badly limited by specific knowledge and basic intelligence here :duh:

 

[Greywolf]

I am not a carb guy at all, so I apologize if I'm off base, but I think the reason for Dean's concern about the duplicated carbs has to do with intake velocity.

Since you're now taking 1/2 or less of the original airflow through each venturi:
P1V1=P2V2 for airflow/pressure through an orifice.
That is, the original pressure (air pressure in absolute psi, that is, 14.7=atmospheric) multiplied by the velocity in inches/second of the air at the orifice, will equal the multiplied sum of the pressure and velocity on the other side.

And velocity through an orifice changes by the area. Larger area=lower velocity for the same volume of airflow (or liquid). Meaning if the volume is lower (because it's now split between two carbs) and the area is doubled (because it's now two carbs worth) velocity will be down significantly. Not sure if it's directly proportional but I think it would be. It's been too long since I've had to think about Bernoulli or Boyle, I been playing with Watt and Ohm too much lately.

So if you have the same size venturi being fed with a smaller volume, you'll have less velocity through the carb stack and fuel feed may be significantly different than intended. You'll have to re-jet at the very least (of course you knew that), but if idle airflow is too low, even re-jetting may not provide adequate fuel (which is why a lot of multi-carb setups are progressive...although that's hard to do with an IR setup).

Dean is concerned your setup may not idle.

 

[Anonymous]

I don't know if this is true of mild street engines, but race engines with IR induction systems get problems with stand-off because of pulsing and wave action, which complicates jetting (and the racing outboards I dealt with were extremely crude . . . and mainly had to run well only at WOT). Dean will surely let us know if this IS a consideration in my parts-chaser vehicle, where the runners are going to be so short (wild-guess: 8-9"?) that my street engine should never wind up high enough to get into the region of well-defined resonant waves.

It's likely that a dabbler like me shouldn't mess with this sort of thing on his basic transportation. But I've been reading about IR Webers for so long, I thought I should get off the pot . . . . :rolflmao:

 

[xctasy]

Fuel standoff and pulse tuning are the reason that IR setups are normally based on time honoured Weber/ Dell Orto/Mikuni/Amal/Lectron systems.

According to Vizard, Braden, Barry Grant et al, in any non IR Holley, they hate long duration cams, as the venturis are short and not suited to controlling fuel standoff, especially when the choke circuit is so close to the top of the boosters. Stock soution for 4500 series Dominators is to update to a custom made longer booster venturi. Those custom parts can be transferred with a bit of maching to the old standard 2300/ 4150/4160/4165/4175/4180 carbs, but not the 4360 or 1946/2210 series carbs from the mid to late 70's.

So you just have to find ways to cope with the pulsating and oscillationg intake 'slugs' as each barrel isn't serving 4 cylinders every 720 degrees. The 2-bbl 2210 then has to deal with a cagy, hairy air flow signal. In its stock environ (the International Harvester Scout 345/ Mopar 318/360/383/400) its under a really nice, huge vac signal. Easy to get easy flow from each orifce, wether it be idle air bleads, power valve or booster venturis or jets.

The ways through that are to reduce the axuliary fuel supply that is designed to cope with many sqaure inches of wetted perimeter requiring fuel when a V8 cracks open to wide open throttle. In IR systems, there is next to no time of concentration or wetted perimeter to add, and the fuel goes right to the source. So your squirters need less volume and capacity.

Meantime, just hook the 2-bbls up as an IR system, and reduce the power valve size by fuse wire firstly, and then rework the idle and richness to suit by breaking intothe lead plugs. If its reverse idle, then you'll need to have a think on what you'll do, but as long as you've got the main jet sized to suit, you should be okay.

Your 2210 carbs existing venturi diameters define where the power will be in the rev range, and you can only customise that about 125 thou up before breaking into the casting, or maybee down 125 if you alloy sleave. either way, that defines your main jet size, and it must be actaly right in terms of cc/min discharge to make the power you are aiming for. IR systems a very specific, just like 80% dutry rasting figures for injector sizing on an EFI engine.

I don't have any info on your 2210. The seventh post down in viewtopic.php?f=5&t=8106&start=0 has some data which might help.

The data for definig exact cc/min for your application just has to be interpolated between ventri size and this post

 

[MustangSix]

It might be cheaper and easier to set up some bike carbs. Mikuni carbs are dirt cheap and are designed to operate as an IR. You just need a suitable air filter or airbox.

Some may recall that I attempted this with six Mikunis on a crossflow, but synching up all of them was too hard. Four wouldn't be a problem. I also had to add a pressure regulator to keep the fuel at 1.5 psi. Bike carbs are usually gravity feed and don't like a lot of fuel pressure.

 

[Greywolf]

It might be cheaper and easier to set up some bike carbs. Mikuni carbs are dirt cheap and are designed to operate as an IR. You just need a suitable air filter or airbox.

Some may recall that I attempted this with six Mikunis on a crossflow, but synching up all of them was too hard. Four wouldn't be a problem. I also had to add a pressure regulator to keep the fuel at 1.5 psi. Bike carbs are usually gravity feed and don't like a lot of fuel pressure.

That looks eeerily like my old Triumph Spitfire under the hood (except mine had the GT6 engine). Just a spot of nostalgia.

 

[xctasy]

#10+

The Mikunis would be an ideal first start on a 4 cyl application

Only problem is they do start taking up some space unless you make a shorter manifold for them.

If your serious, I'd use Mikunis first to baseline maximum power, idle an progression. Vizard and others found 44 mm brilliant on Baja dirt racers for Pinto engines, able to be tuned and can take the abuse.

For packaging, a set of 2210 Holleys would work better, but unless you can get the carb's venturi area up to taht of some RC40 Flatsides or 44s, you won't get the power. Any IR set-up will start to gain power over a single 2-bbl on a 4-cyl engine, but to make them pulse tune, you have to have less than 22 cubic inches of engine per sq in of venturi area, or else theres really no point. From memory, irrespective of what IR set-up you use, for 122 cubes, you'd need a minimum of 5.5 sq in of total carb venturi area just to get abot 140 hp at 5200-5400 rpm.

 

[Beemer+ford6lover]

If you do decide to try the motorcycle carbs, try to stay away from the cv(constant velocity) style carbs, they almost always give problems with tuning when you have individual filters unles you run a longer rubber peice between the filter and the carb. Honestly flatslide carbs would work the best, i would look for a set of carbs off of something like a yamaha xs750 triple. That way you can get two sets of carbs of 3 each connected. Now for specifics with tuning the carbs, they are way simpler than a car carb, its all about 1/4 throttle primary jets, 1/4-3/4 is needle jet, and then 3/4 on is the main jet. The thing you will have to remember is motorcycle carbs are all about instantanous throttle response. where as carbs designed for cars are typically design with cruising more in mind so i wouldn't expect them to get you any mpg gains because modualting the throttle and keeping it steady for cruising will be slightly harder.

 

[Beemer+ford6lover]

It might be cheaper and easier to set up some bike carbs. Mikuni carbs are dirt cheap and are designed to operate as an IR. You just need a suitable air filter or airbox.

Some may recall that I attempted this with six Mikunis on a crossflow, but synching up all of them was too hard. Four wouldn't be a problem. I also had to add a pressure regulator to keep the fuel at 1.5 psi. Bike carbs are usually gravity feed and don't like a lot of fuel pressure.

By the way are those mikuni RS series carbs with the accelarator pumps?

 

[Anonymous]

I thought about using the 2210 because it's unused NOS sitting in a box on the shelf for decades, but as I mostly expected it sounds from what you say, Dean, that it would be sub-standard in the end, and that a second DCNF Weber is the smarter choice.

I've had some experience setting up slide-valve Mikunis, years ago, and like that idea, too. We always rubber-mounted them against wear from vibration, though this Mitsu four, balanced during the rebuild and having counter-balance shafts madly whirling about on either side of the crankshaft, is a lot smoother than most Mikuni applications. I never got to fiddle with a Mikuni with an accelerator pump, though; what did they come on?

Beemer+ford, that's a good point about a too-responsive throttle being undesirable on a street car; would be especially bad with cable-type throttles, which always seem to have a little stiction regardless of how you lube them (cable-operated clutches are worse). Pushrod throttles were another feature of older cars that seem superior. Of course, Toyota's fly-by-wire electronic throttles had no stiction, did they . . . .

 

[Beemer+ford6lover]

I think all the rs series mikunis have accelerator pumps in them and are typically found on late 80's and up early 2000 model sport bikes. they came in a variety of sizes from 32mm to 46mm i think. Lol, there are so many different kinds of motorcycle carbs that operate differently its really hard to remember them all. I'm more familiar with early carbs up until about mid 80's though i'd love a set ot the rs 34's for my kz1000 just to make it easier to tune. You can adjust the needle in them on without removing the entire carb to get to them on a bike. unlike my bs 34's on my bike.

 

[xctasy]

Response time is power if its a car or bike. On a car, the engine is in transition more often, as the power to weight ratios are worse and total frontal area sap reserve power. There is also a flywheel effect which slows the throttle events.

Due to the scaled down lowering of rpm at peak power, cars seam to have have proportionally more torque down low, and different gear ratios slow the time factor. However, its just a scaled bike performance curve where maximum torque is a function of the 5252 rpm power= torque function.

Mikunis are just like Weber IR set-ups...just like Webers or any IR set up, with no other mods, they always make up to 25% more power over a six cylinder per throttle system (refer to the 16% we found Big Six forum back in 2007 with pssnmn1 Bill in Indy on the Desktop Dyno program run out on a stock 1-bbl 300 vs one with six barrels viewtopic.php?f=2&t=42347 ), and about 10 to 12% over a good three SU system on a six cylinder car (Aston Martin DB6 with triple 2" SU's vs Vantage with DCOE 45'S and 40 mm venturs, 285 vs 314 hp). Another compariosn from Aussie Chrysler Hemi 6:The 38 mm choke DCOE 45'S on the 1971 E48 Charger vs the 216 hp on the Carter 318 carbed 2-bbl 265 Hemi E37 Valiant Charger, thats a 15% boost with stock cam and exhast just by going IR. So the change to independent runner is always worth at least 10%, and often up to 25%

Similar with Ford Pinto 2000's. You get as much power out of 44mm Mikunis as you do DCOE 45 Webers with 40 mm chokes. 155 hp or more at 6500 rpm is not uncommon.

 

[MustangSix]

Most constant velocity carbs like SU's, Stromberg CD's, and Mikuni's don't have or need accelerator pumps.

The interesting thing about IR setups is the total airflow possible. With shared plenums under a typical 2bbl or 4bbl you wouldn't expect to need a carb any bigger than 400-500 cfm on 4 to 5 liter engine. But when you look at a typical 40mm DCOE or similar IR setup, the total available airflow can be well over 1000 cfm.