Need Carb selection help

[Johnsondawg]

Well I'm new here so I'll give a short background. I'm replacing the 170 in my 66 Bronco with a 200 from a 68 Mustang. I have the engine built but need help deciding on a carb. So here is what I have so far. The 200 has been completely rebuilt. For the rebuild, the engine was bored .030 over. In addition, the original head was traded out for an 81 fairmont head for the larger valves.. To regain compression lost by the larger combustion chamber of the newer head, I had the head milled down .060. Other than that, the rebuild is basic. The Cam is the stock spec cam that came in the rebuild kit. This Bronco is a daily driver and it will be mated to a C4 transmission. So is the original Carb gonna be big enough? I also own a Weber 38 DGES Carburetor (Synchronus Carburetor) but I'm afraid its a bit to much carb. So what carb should I use?

 

[JackFish]

The cam and induction won't be able to utilize the full potential of the 2bbl.
But it would probably make more power.
The 1bbl will probably have more low-end torque, which is what you might be looking for.
A double-roller timing chain from mike advanced four degrees will give you even more bottom end.
I have a fully ported head and hipo cam running a 1bbl, but I did go up a jet size.

 

[CZLN6]

Howdy Johnson:

And welcome to The Forum.

Q- "So is the original Carb gonna be big enough?"
A- An original '66 Autolite 1100 is rated @ 150 cfm as compared to 185 cfm 1100s on a 200 engine. So the answer is no, not big enough for getting the most out of your engine. It will give very good low end power and good throttle response. Depending on the stock carb mounting adapter on the '80 head you may have to use the mounting adapter from the '66 head. The '66 170 carb, if it was running good would make a good carb for breaking in the rebuilt engine- depending on what distributor you have. The '66 carb and distributor are designed to work together with a Spark Control Valve (SCV) in the carb to the Load-O-Matic distributor. If you change to a '68 and later carb you will want to upgrade your distributor too.

Q- "I also own a Weber 38 DGES Carburetor (Synchronus Carburetor) but I'm afraid its a bit to much carb."
A- The weber is rated at 360 cfm which would be great for top end, but likely too much for a clean low end. It would also require an adapter or a modified log to fit. It is a very sophisticated carb with lots of tuneability, but that take time and knowledge of how to go about it.

Q- "So what carb should I use?"
A- Since you have the later head you have several good choices for a one barrel. A couple questions will need answereing first- What distributor are you using? Do you intend to use the stock throttle linkage? Either a '68 points distributor or the Dura Spark II from the '81 head donor will be an upgrade over the original '66 Load-O-Matic distributor. Both will do best with a carb with a ported vacuum signal from the carb for vacuum advance. Only one upgrade carb will match up with your stock mechanical linkage. That is an Autolite 1101 from a '69 Mustang with a 250 engine. It is rated at 210 CFM. An 1101 will be identical in appearance to your stock '66 1100. The differences are on the inside.

The other one barrel choices will require adaptation or conversion to a cable throttle linkage system, mounting and fuel line. The Carter YF from a 200 from '70 to '79, is rated at 187 cfm and the Carter RBS rated at 215 cfm Used on 250 engines from 1970 to '74, are both good choices. The stock '80 Holley 1946 is also a possibility, but not a preferred one. It is a very complex carb and not as easily tuned as the others.

The other possibility is to upgrade to an Autolite 2100 two barrel carb. It would require an adapter or a modified log to mount it. All 2100s have an annular discharge venturi booster system that makes for great throttle response and low end. they come in a variety of sizes ranging from 190 to 350 cfm, are incredably durable, and may be the world's easiest carb to rebuild and to tune. Check them out.

Thanks for sharing and again welcome. Keep us posted on what you decide and how it works for you.

Adios, David

 

[Johnsondawg]

Thanks for the info. A few more bits of information.

First, I already have a throttle cable instead of linkage so I think that will open up my options a little or at least make a change easier.

Second, I already run a duraspark Ignition, I changed the ignition but not the carb yet so I run manifold vacuum to the dizzy for now.

Third, I have two autolite 1bbls. I have the one from the 170 (Load-o-matic) and it has no issues. I also have the one that was on the 200 Mustang motor. It is not load-o-matic but I don't know if its an 1100 or an 1101. It has a " remanufactured " sticker on it. I know this carb works because It was on the 200 when I got it and I started it before I bought the engine. How can I ID this carb?

My concern with the autolites is that the carb opening in the log intake is larger than the opening on the carb. Is that really a problem?

I drive this Bronco every day to work so most of its use is on the street but it will do the occasional camping and hunting trip. I have another Bronco for the serious off roading ( 74 with a 351w, EFI, 35" tires etc ) The point is its primarily a commuter. with my 170 , the three speed, and 4:11 gears I can almost hit 70MPH down hill with a tail wind. I would like to be able to run 75 MPH or more so I can get on the Interstate without fear of being run down. That said, I can't imagine that I would feel comfortable going much more than 80MPH in a 66 Bronco. So in a perfect world, I would like to keep as much low end as possible while still being comfortable getting on the highway from time to time. If I can do that and come up with "reasonable" mileage I would be pretty happy. I'm really not sure what to expect going from the 170 to the 200. The 170 actually runs very well so its not like I'm going from a very tired 170 to a fresh 200.

I believe I also have an Autolite 2100 in the garage some place but I know it would require a total rebuild to use it.

 

[Johnsondawg]

One more thing, can I upload pics here or do I need to upload someplace else and link them back here?

 

[bubba22349]

It is not load-o-matic but I don't know if its an 1100 or an 1101.

From a 68 200, than it's an 1101 so it would work good with the DSII

 

[Johnsondawg]

It is not load-o-matic but I don't know if its an 1100 or an 1101.

From a 68 200, than it's an 1101 so it would work good with the DSII

Thats what I was thinking but my concern is that its a reman unit so I know its not original. I got the C4 that I will be using from the same vehicle and its out of a 79-80 fairmont according to the numbers on it. So that makes me think alot of changes could have been made before I got it. I guess I could start with the carb from the mustang and make changes later if I need to. I got the Weber 38 DGES thinking it might work for this project but maybe I could sell it and use the money for something else. It was given to me so I don't really have anything into it. What would that carb be worth if I sold it? Its very clean and I'm told by my friend that gave it to me that its in good working order.

 

[CZLN6]

Howdy Again:

Fyi- the weber is quite and expensive carb so it could buy you a good bit.

The easy ID on the 1101 is to measure to throttle bore (Bottom). All 1100s have a TB of 1 7/16". All 1101s hav a TB of 1 11/16". The other difference is the inner diameter of the venturi. The 1100 for a 200 is 1.2". An 1101s inner Diameter is 1.29". The '68 & '69 200s 1100 is down sized to 150 cfm, but has no SCV.

Both the 1101 and the Carter RBS have a TB that's closer to the 1.75" TB of the later head.

Do you have any idea what your RPM is when cruising at 70 mph?

Keep it coming.

Adios, David

 

[Johnsondawg]

Howdy Again:

Fyi- the weber is quite and expensive carb so it could buy you a good bit.

The easy ID on the 1101 is to measure to throttle bore (Bottom). All 1100s have a TB of 1 7/16". All 1101s hav a TB of 1 11/16". The other difference is the inner diameter of the venturi. The 100 for a 200 is 1.2". An 1101s inner Diameter is 1.29". The '68 & '69 200s 1100 is down sized to 150 cfm, but has not SCV.

Both the 1101 and the Carter RBS have a TB that's closer to the 1.75" TB of the later head.

Do you have any idea what your RPM is when cruising at 70 mph?

Keep it coming.

Adios, David

I don't have a tach but I could get one hooked up easy enough. Just so were all on the same page, I still have the 170 in it not the 200. Are we assuming that the 170 and 200 will run at similar RPM's at the same speed? The 200 is on the stand waiting to go in. I need to decide what my order of events will be. Do I drop in the 200 now or wait till I have the C4 ready and do it all at once? The other option is get the C4 installed and do the 200 later. I'll get a measurement on the carb in little bit.

 

[jahearne]

The 200 will drop right in and bolt up to your 3-speed. Will your C4 mate to your transfer case? The 3-speed and C4 both have 1:1 top gear, so you may not get better RPM on the freeway with those 4:11s. The 200 may run better at a higher rpm than the 170 especially if it was balanced. While the 200 is on the stand, put a set of ARP rod bolts in it for a little insurance at hi revs. At high RPMs you'll want the biggest carb it can handle. I like the Carter RBS on my last 250. It ran great with a 264/274 dual pattern cam and 5-speed. If you're running a stock cam right now, a set of 1.6 ratio rocker arms will help out a lot, but they're not cheap. For less money (or about the same) you can replace the stock cam and timing chain and use the adjutable rocker arms from the 170.

 

[Johnsondawg]

I think I have the C4 situation figured out. The truth is I have some help from a fellow bronco guru who knows alot more about automatic transmissions than I do. I have a Bronco C4 intermediate housing and output shaft that will be installed in the C4 along with other upgrades like V8 clutch packs , H servo, and shift kit. I'm also using an auto tilt column from a van to do the shifting. If the measurements are correct, the transfer case will move back around 2 inches.

I have thought about changing the cam before the install but it would delay the install a bit. I'm certainly not an expert engine builder so I would love to hear cam recommendations.

Also, my other carb is not looking like its an 1101 as the measurement looks to be 1 7/16" not 1 11/16".......Damn!