Technical Intakes.switching a 3x2 to a single 4

So on my sbc I've switched to 3x2,I've done everything to build them right,progressive,blocked idle circuits,low fuel pressure,all that jazz. The car still has a noticable less radical idle with this intake. I've ran a stock cast intake and a 4brl,and also a holly single plane and it idled,and loped very nice. Every time I slap on my 3x2 my cam sounds like it's gone,almost as if it's not getting enough fuel in all the cylinders as well. I've sorta given up on it after all this time, wondering what you guys think of spying a single 4 tunnel ram? The did run good with my old single plane on it.

My setup is,355 chev,headers,comp 268xe cam,3000stall converter,3.08 gears in a pretty light fender less A coupe. (And yes I'm pretty happy with that gear in this particular car) yes the 3x2 looks good,but I'm over the issues it is causing,it even tends to 'go' when I'm sitting at a light. and I do like the look of tunnel Rams. I know it may not be everyone's cup of tea. Also thinking on a nice duel plane air gap style intake.ill perhaps go back to 3x2 later but for the summer I just want to enjoy the car...and hear the cam again!

 

3 x94s= about 425 CFM's
I had a 327 with all most 400 hp with 750 vac in a 3,400 pd car 7.85 (1/8th)
3:55 gear 28 tall .
Same motor in a 2,600 pd car , would not fall out of a tree with 3 x94's
So I pulled the 3 Carb's off & back to a Single 4

To be different on my A ,
I run a Victor Ram on my SBC with 2 x 525 two barrel's Holley Race carb's ( big inch SB )

 

I've ran this car out of fuel before and these 3x2 I swear has the same sound that it had when it was running out of fuel. I think they are just not enough for the cam I have.

So you think i just don't have enough cfm?

I just don't know if a single 650 on a single tunnel ram will run good either but my single plane ran well. I know sir gaps are supposed to be one of the best but doesn't have the look (same reason I took off the single plane)

 

Yes a single carb will work , but A tunnel ram rpm range is about 4,500 to 8000 RPMs or so ,
If your motor is pretty much stock , don't expect it to Perform Well ,(No bottom end )

 

If your outer carbs are not true outer carbs then they are probably leaking air past the blades. No idle circuit means just air is leaking past the blades. More air less fuel will do two things it will speed the idle up and it will have a less noticeable lope at idle.

Maybe try fattening the idle up on the primary carb. it should help with the tip over as well.

 

What carbs to you have on the tripower? 94'S? or Rochester's? 94's are not near enough to run progressive on that motor. if you are running 94's try running them all straight up, no progressive linkage. you will be surprised how much it helps. if it is rochesters, you need to check your metering rods and jets and make sure that you don't just have it jetted to lean. a Rochester 3x@ set up should work just fine with that motor combination. Regardless of what you do with the 3 X 2 setup, a good tuned single 4 barrel will almost always perform better.

 

They are ford 94's the carb guru on here instructed me on how to set them up. The punters are not leaking air,I have used the special glue to seal the blades at idle. Also they won't be working as idle carbs cause the circuits are now blocked

 

You may on to something tho with returning the outer carbs back to idle carbs

 

Whats the point using dinky 94's? Go with a single 650 CFM four barrel and get you some performance.

 

So you have to remember that CFM of a carburetor should not effect much feel of an engine below 1/2 throttle, and will only effect peak performance when radically different. What you are experiencing is an air/fuel ratio problem. It seems for you, that most everywhere throughout your rpm range, you're not getting enough fuel.

The problem that most people have with carb tuning is that they can't leave one thing alone while messing with another. The very first thing that needs to be done is find the proper idle fuel mixture. This can be relatively lean on cars with accelerator pumps and power valves, but remember, adjust this well because it's a good part of your cruising mixture as well. (No I'm not going to instruct you how to adjust your carbs, just guide the whole process a bit)

Next, you need to guesstimate your main circuit fuel needs. Now remember, if your running 8BA carbs, you're going to run somewhere around a 50-55 jet. Remember, the jet is in relation to the air flow of the carb, not the engine. A 750 CFM carb will always need bigger jets on the same motor than a 500cfm.

Now it's time to consider the enrichener circuit. In the 8BA it is a vacuum actuated power valve setup. These carbs are tricky because the power valves are hard to find. BUT, you certainly can not run the stock power valves, due to the significant increase in throttle plate area. Typically trips will run 3.5"/Hg valves to make sure the enrichener circuit actuates on time and isn't just dumping fuel ALL THE TIME, which can make carb tuning a NIGHTMARE.

Finally, it's time to meter your air. This is done by adjusting the throttle linkage and air bleeds(of your carb has them) typically progressive linkage can be a nightmare, BUT if you decide how you want the carbs to operate before you start adjusting, it's easier to aim for that specific end goal. Otherwise it's a constant battle of adjusting for drivability or all out performance. I prefer a 2/3 throw on the center carb and the outer 2 come in quickly through the last 1/3, but that's just me. It's really all preference here. Just remember that anyone who says a hot 350 won't run on a single 2 bbl has never driven one. As long as the air fuel ratio is right and the transition between idle circuits, main circuits, and enrichener are working properly, the engine will behave absolutely fine until the airflow of the carb effects overall power. It doesn't matter to the engine if you're asking for 150cfm of air fuel mixture from a 170 CFM carb or a 700 CFM carb, as long as the mixture is right.


Sorry for rambling, hope this helps.

 

Re-read Beaner's post. He's got it right

 

What's the point of dinky 94's?? Well it's a hotrod website,and s single 4 really isn't traditional. I think we all here would prefer 3x2 IF they ran the right way. I'm just getting tired of messing with them and I'm just frankly not knowledgeable enough with them to get them to work right

 

Neverdun, wow,no you're not rambling. I appreciate that write up. But honestly it's a bit over my head I can admit.

My linkage is setup how you say about 2/3. Not sure what my jets are in my center carb,they are from dickster here. He has set me up this far. My car also tends to randomly get fuel and want to take off. It's not bad,but it's annoying. So just getting new bases with idle circuits and adding the missing idle parts to the outer carbs will not remedy my issue?

 

I'll trade ya the 3x2 for a tunnel ram!

 

You might take offence, but your knowledge of why the car sometimes takes off at a stop, is at fault. It is not randomly getting more fuel when it does that. If it is random, this is a perfect symptom of carbs throttle plates not sealing correctly each/every time the throttle is used, then relaxed.

If it was fuel, the idle would drop, not rise, and probably stall, run black smoke.

Carbs not sealing at random times can be one or more carbs with an issue, also linkage problems, springs not right, etc. It also can be wear on throttle blade shafts, that prevent the blades to stay perfectly centered, and be able to close tight, each and every time, even letting the carbs close very slowly or very fast.........it should always idle the same.

Not all brands of trips are touchy: I have used original Rochester factory tri-power carbs on and off since late 60s, and they all have run so perfect and always went back to correct idle each time. I have never wanted the modded fake Rochesters, as the originals seem to always be available.

.

 

El Scotto, I'm aware of the price diff. I think I'll decline!

F&j, no offense taken. You are not rude,and I agree with what you are saying.

I think I'm going to throw on a cheap air gap and known good 4br to drive it while I work on re doing my tri power setup. I can use the intake and carb on another car once the 3x2 is back up and working. Will save me some cash right now and get me up and running again. I don't like the idea of giving up,so I think this is the best compromise for now

 

You can't set up 3 94 carbs like 3 rochesters and expect it to work like 3 rochesters. You prolly need 6 94 carbs just to get close.

A tuned single 4 bbl will always out run a poorly set up and out of tune 3x2 set up. Also A single 4 won't ever look as cool nor ever give you the awesome sound and kick in the pants when the other 2 carbs kick in.

 

31vicky, yeah I agree with ya

 

Anyone know where I can find aftermarket primary carb bases? I thought they used to be 80$ each seems now they are over 100 each

 

A set of 94's on a sbc is sweet, made for each other. The idle ckt is too small in your primary carb, it is designed to supply fuel to a flattie, the sbc needs more fuel. Locate whats called the 'idle resrictors' (brass tubes) and drill the pinched end to .031 and you'll be good to go.
Stay with the cast iron bases, Holley/Ford made them that way for a very good reason.

 

I'm not sure what the idle restrictors are

I figured my bases are not good like others have stated they are a bit worn in the shaft area.was thinking of turning them into working carbs,that may fix the problem of them leaking out of their throttle shaft also

 

Oh and also forgot to mention when I'm cruising in town (not highway) the engine is sorta sputtering like it's not running right,hard to describe,when I give it a bit more throttle it will start to run just fine but when I'm at a very low cruising speed (almost no throttle) it sounds like it's breaking up till I go above that speed (highway speed it runs just fine) and that's still using the center carb.my outer carbs only are used for on ramps or very hard take offs,otherwise it's just the center,any time that I'm giving the center carb input,in runs fine. Any time that it's left to do its own thing it runs Not like it's old self

 

That is classic surge, caused by too lean idle circuit. Puttin thru town you are on the idle circuit and it is supplying just enough fuel to run a stock flattie. Get a diagram of the holley 94 and you'll find the restrictors, you get to them from the top they are the screwdriver head seen on top of the crossover tubes. Unscrew them and the small hole at the other end is the problem, it is about .022ish and you'll need about .031 to get enough fuel. You'll be good to go when you drill them out.

 

Scotto,
That's just plane mean. Besides I was going to trade him a tricked out holley on a Contender intake.

Ok back on track, if I am setting up a multi carb intake 2, 3, 27?they are running on a common plenum I don't delete the idle circuits unless I have outboard specific (secondary) carbs. Number one if you have air going past the butterfly you need fuel going a past the butterfly and two it is just easier to tune.

Number two if you have a single carb running the show and you have air going past the butterflies on the other carbs that single idle circuit better be one FAT SOB.

You need to maintain about 14:1 (as much as 15:1) air to fuel ratio. That is 14 parts air to 1 part fuel (with gasoline), I say as much as 15:1 because our gasoline is contaminated with corn squeezins these days. It is going to be hard for a single small 2 bbl to over come a major vacuum leak and if you have carbs that don't shut the air off you have a major vacuum leak, way better for those carbs to be dumping some fuel.

 

The leaking throttle shafts are not hard to fix. I had the same problem, and got some oversized shafts from Mac's. I bought the proper reamer from Amazon; it was pretty cheap (about $10). Carefully ream the bases and install the new shafts. The throttle arms on the Mac's shafts are kinda chessy and held on with screws. I ground the peening off the original shafts and used the original throttle arms on the Mac's shafts. I "Loc-tited" the screws in place, just to be sure.

 

Now we are getting somewhere. Thanks for the info guys. So I probably should find more bases tho I'm assuming to get some more carb going (so to speak)

 

you will also need the secondary butterflies for those carbs. they are thicker and seal at a different angle than the stock butterflies and will definitely help with sealing up the secondary carbs when not in use.

http://www.speedwaymotors.com/Ford-Holley-94-Secondary-Carb-Throttle-Plate,7128.html

 

I have them in the end carbs now

 

I'll be the first to tell you I'm no carb expert. However since you are running a progressive linkage could you block off the outer carbs and tune the center carb independently? Once your happy with it bring the other two carbs into the mix and address any problems that come up. At that point you know it's the end carbs that need tuned.

 

I would not run a Single 4 barrel tunnel ram. Not only do they not work very well over a very wide RPM range, they also look like you couldn't afford a Dual and "Settled". I'd run an old style single 4 barrel manifold like the Weiand Action +, or an OFFY with a Holley 1850 or a Q-Jet and keep an early vibe to it.