Novice question I'm sure.

My truck has a adaptor plate on my stock intake, and on it resides a 4 barrel edelbrock carb.

I'm trying to go back to the stock Motorcraft 2150 2v carb.

I was going to order a rebuilt from National Carburetors ($159, $40 core). There are options for "Climatic Choke" or electric. I've read up on the differences, and am not sure which to order. I'm trying to avoid "oh well you HAD this, so now you need to buy this", etc.

Any extra stuff that I'll need to keep in mind during ordering?

Thanks for any insight.

 

Be aware that "electric" in the context of a factory choke is actually "electric assist," meaning it does not function without the hot-air (often called climatic) mechanism in place. So for starters, be sure of what you're getting.

If you're comparing a true fully-electric choke (as would be the case with an aftermarket Holley or Edelbrock carburetor) against a stock-style hot-air choke, it's not even an argument. You want the choke position to track true engine temperature and a hot-air choke is the only mechanism capable of doing so. A true fully-electric choke opens at the same rate for a given index regardless of how much the engine is struggling to warm up. True fully electric chokes operate asynchronously to engine temperature. True fully electric chokes are used in cases where it's inconvenient or impossible to reconstruct the factory-style heat crossover to operate a climatic choke. Factory electric-assist chokes, on the other hand, were built as a means to open the choke plate faster for reduced emissions. It's not an either-or. Factory electric-assist chokes have a built-in temperature cut off to keep them OFF until they reach a certain temperature, so they won't move until the hot-air mechanism gives them a "push."

Understand that if you're buying a stock-style rebuilt carburetor and they talk about "electric choke," they're probably talking about electric assist, in which case you need the hot-air portion anyway, otherwise the choke won't ever open. You need to understand what you're buying. I don't know what this place is selling so I can't comment, but factory electric-assist chokes are easy to spot.

 

Thanks again for great info, fmc400.

The only thing the web page shows difference in the models is the part # (Model 2150, part #ND2891 Climatic or #ND2889 Electric)
http://www.nationalcarburetors.com/cat-fordtruck.html

I'm guessing since my truck currently has an Edelbrock (true electric choke), I need to find some resource to convert it back to factory electric-assist choke to get a stock replacement carb, or I just go with an aftermarket 2v carb w/true electric choke.

 

Your thinking is correct. If the replacement carburetor you're looking at has an electric-assist choke and you have no existing provisions for a hot-air choke, you'll need to add such provisions, or convert to a true fully-electric choke on the replacement 2-barrel. That's easy enough, just not as ideal as the factory hot-air setup. The other possibility is that this vendor is actually selling a true fully-electric choke.

Out of curiosity, what Edelbrock carburetor do you have on there now? Are you running a 4-barrel with some sort of adapter for a 2-barrel manifold, or are you swapping manifolds too?

 

It's the stock intake with an adaptor plate. I want to keep the stock intake. The carb needs a rebuild, so instead of rebuilding the Edelbrock, I figured I'd just "fix" it back to what its supposed to be.

 

Got it. Since you're working with an otherwise stock setup, you likely have provisions for the hot-air stove. If it has been broken off, it can be repaired with a kit or piece of brake line. It's a pretty common procedure.

Edelbrocks are also fairly easy to rebuild; the cost of a kit and Chem Dip would come out cheaper than the 2-barrel you're looking at. It's just another option. I can understand wanting to put it back to somewhat original, especially since you're not getting the full benefit of the 4-barrel anyway.

 

I've got a similar situation. 390 with a stock 4bbl manifold and an edelbrock 1407 (750 cfm) on it. This motor came from a 65 galaxie 500, has 10.1 to 1 compression and from the factory developed 300 hp. I'm mile high in Denver and the truck runs super rich and gets like 4 mpg (or something terrible like that). I tried smaller jets and it was lurching in what Edelbrock calls "cruise mode" ( high vacuum, low power). I'm not racing or hauling huge loads. I want better mileage, so I want to put a 2150 2bbl on it, with a manual choke.

Wondering if anyone knows which of the 2150s would be right for it (or maybe which jets and metering rods in a 2150 would be right for it) and where to get it plus a 4bbl to 2bbl adaptor. Thanks for any suggestions.

 

HUmm..... Typical. I hunted around and couldn't find what I needed. As soon as I posted here looking for help, my next two searches came up with National Carburetor in FL. It looks like they have everything I need, except they don't list a manual choke option -- but I know that conversion is simple. Good prices too. Their number is 904 636 9400 Hopefully, that answers my own question.

 

Something else you might consider. The 2100/2150 carbs are simple as dirt to tune, but getting the small parts can be a pain sometimes. If National Carburetor doesn't work out, consider using a 2300 series Holley 2bbl. instead.
You could get an adjustable jet kit from Summit that allows you to adjust the mixture without tearing down the carb and changing out the jets.
http://www.summitracing.com/search/p...0%2B4294947102
Summit also has the 4 to 2 bbl adapters.

 

I would avoid changing to a 2-barrel on your 4-barrel manifold. Often times, the primaries on a 4-barrel are smaller than the bores of the 2-barrel, so you can theoretically get a little better mileage with a 4-barrel if you keep your foot out of it (which, understandably is hard to do).

First of all, you need to calculate what your mileage actually is. When someone says "something like," that means they haven't taken controlled measurements. It's easy to think you're getting awful mileage if you simply fill up a lot. It's highly unlikely you're actually getting 4 MPG. You need to actually calculate your mileage at the pump to see where you're at. You should be able to approach 8 to 10 mpg if properly tuned and you exercise good driving habits. I would want to keep the 4-barrel there so that the power was there if needed. Your engine is set up for that anyway.

 

Thanks. That makes good sense to me. Well it probably is better than 4 mpg, but it's really low. I just drove it under 10 miles across town and back, and the gauge dropped a full needle width. I will calculate mileage, but I'm pretty sure this 750 cfm Edelbrock 4bbl (model 1407) is too big for this application. Plugs and tail pipes are back sooty. Everything I've read says 600 CFM is right for the 390 (at least in a normal truck). The guy at National Carburetor also said 600 CFM was right for 390 in an F250. I'm going to double check timing also, but I'm pretty sure that's not the problem.

I went ahead and ordered a Holley 1850 4bbl, 600 CFM from National Carburetor for $210, including shipping. They'll jet it for 5,000 feet (I'm outside of Denver). The 1850 has manual choke, which I like.

I heard both ways on 2 bbl vs 4 bbl, but went with the theory that staying out of the pedal on a 4 bbl will be as good as, or better, mileage - and you've got secondaries available to pull hills or loads. 4 bbl also means no conversion adapter or changing manifold for me. The guy at National Carburetor liked Holleys over Edelbrocks because he said Holleys open the secondary with vacuum, not a mechanical lever, so they're more truly responsive to the actual need for fuel. Frankly, I dunno, but it sounds good to me.

 

I just re-timed my 390. I'm at 5,300 ft elevation. It's out of a 65 Galaxie 500. It has 10.1 to 1 compression. It was set at 14 btdc. I set it to 16. But I really have no idea where it ought to be. I'll drive it and see if it pings or knocks. The 360 in my old 75 that I sold was always at 10 btdc and seemed happy there.

TIming may need to be dialed in better, but I'm still pretty sure the Edelbrock 750 FCM is just too big for that motor, at least as it's built running in a standard issue 4x4 highboy.

 

Further update: Looking more closely at timing.... I know it's off the topic for this thread, but the carb questions led me to timing - and that's where I think most of my problems were. I found the vacuum advance wasn't working (leaking diaphragm), so I replaced it. I also put the timing light on it and found that (with the vacuum advance disconnected) I could set the initial advance to 10 degrees BTDC, and when I revved it up over 2500 rpm to check total advance, it advanced up to 36 degrees. But when I let off throttle and it returned to idle, it did not return to 10 degrees, but stuck at around 16 to 18. Long story short, I put new springs in the centrifugal advance in the distributor and it went right up to 36 and returned right back to 10, as it should. This immediately brought the mileage back into something reasonable, and it runs a whole lot better. Can't do exact MPG calculation, because speedo gear isn't right number of teeth and speedo is reading 8 mph too fast. The distributor springs are made by Mr. Gasket and can be had from O'Reilly's and CarQuest (and probabaly Napa and Autozone, etc...)

THe only timing rub now is that a pretty knowledgeable Highboy mechanic just told me that motor rebuilders he respects are saying that with today's gas, total advance for big block fords should not be more than 26. If that's true, I need to get back into my distributor and figure a way to limit how far the weights can make the reluctor move (limiting total advance). Other threads have suggested ways, but now I'm really off topic for this thread. For distributor advance info see FE Distributor Timing

Back to carburetors, I still think the 750 CFM Edelbrock is too big for my use and elevation. It ain't a race car! So I have a 600 CFM Holley 4 bbl coming, jetted for 5,000 ft. That's from National Carburetor in Florida - I think it cost around $200.

 

As long as you don't experience detonation (pinging, rattling sound under acceleration) leave the timing where it is.
Also, because of the high altitude you can get away with more timing because of the reduced peak cylinder pressure.

 

Mike

Thanks. That sounds good to me. Ran it today on more or less level highway at up to 70 mph carrying no weight with the 10 degree initial advance and 36 degrees total advance and it sure seemed happy. No pinging or rattling.

I had a fairly experienced mechanic tell me he sets timing using only a vacuum gauge. At idle, he advances it to where vacuum is highest, then backs off just a touch and leave it there. Personally, after marking 10, 20, 30 and 36 degrees on the crank and watching the advance with a timing light, I feel like the light shows you more clearly what the advance curve really is. Without the light, I wouldn't have known that the springs were too weak to return the timing to 10 at idle and the weak springs were leaving timing at idle at 16 - 18 (sometimes even 20). Also, with the weak springs, I think it was advancing too quickly - too early in the rpm range. I like using a light, but I'm curious about checking it against the "highest vacuum" method.