Carb and distributor mismatch

[Anonymous]

Hi guys,

With the current price of gas, and the fact that it's way to big for the breathing capabilities of my tired 170 anyhow, I'm going to pull off my motorcraft (non-progressive) 2bbl carb, and put one of my old 1100 1bbl carbs back on. I know they don't work great, but are worth a few mpg until I build my 200 with a better breathing head- hopefully this winter.

I've read several times that the early pre-'67 or '68 carb is not compatible with the later distributor that has both vacuum and mechanical advance. The early carbs are designed to run with the vacuum-only advance distributor. But nobody has ever said what will happen if you do this- too little advance, or too much? I traded my original distributor in for a rebuilt '68 (single vacuum with mechanical advance) distributor, and would like to know what potenial problems I'm in for when I put the early carb back on. Thanks.

Thor

 

[Anonymous]

if you drive her decent doesnt a 2 barrel get better gas mileage then a 1 barrel? I know a k&n air filter is a good investment

 

[cdherman]

Now, you might want to be careful what a guy driving a truck has to say to this topic, but I have done some serious reading about the loadomatic carb/dizzy setups. Tragically, a lot of good stuff right here is no longer searchable after the 11/2003 crash.

My understanding is as follows:

The loadomatic setup uses ported manifold vacuum (from above the throtle plate) until the venturi vacuum exceeds the manifold vacuum. At that point the spark control valve diverts to the venturi source of vacuum. This allows continued spark advance, even in circumstances where the manifold vacuum has fallen (like WOT, under load etc. I think)

You probably knew all that. My understanding is that this loadomatic "circuitry" in the carb looses some vacuum, so to speak. So the loadomatic dizzy was made to be more sensitive/responsive to a given ammount of vacuum. Attaching a non loadomatic carb to a loadomatic dizzy will give too much advance under conditions that produce lots of vacuum (partical throttle, no load), and leave you with no advance when the ported vacuum fails.

Attaching a loadomatic carb to a vac-mech dual advance dizzy will give you less advance from the vacuum canister than you would normally desire, since the vacuum from the loadomatic is inadaquate. You might be able to simply set the intial advance a little high and get by fine.

Later 1101 and 1100 carbs did NOT have the spark control valve and circuitry. For trucks at least, the 65 240 six had loadomatic, the 66 did not. You might wish to get a later 1101 or 1100 without the spark control valve. Or, get a carter YF, which also will work well with your current dizzy, and is purported to get better mileage too. But I have read that folks with mechanical accellerator linkage have more trouble with the YF swap. Most of the remaned YF carbs out there already have the bolt holes to the intake manifold elongated, so they should be a bolt up replacement for your 1100.

later.....

 

[Anonymous]

Exactly. It's not so much that pre-'68 carbs are not compatible with later distributors. The real problem iwhen later carbs are matched with pre-'68 distributors and are not getting enough timing advance.

 

[Anonymous]

hey John, long time! I've been around, but not in the engine forum much as the suspension woes are still following me :roll: What you are saying -

It's not so much that pre-'68 carbs are not compatible with later distributors. The real problem when later carbs are matched with pre-'68 distributors and are not getting enough timing advance.

is the exact opposite of what cd herman is saying-

"Attaching a loadomatic carb to a vac-mech dual advance dizzy will give you less advance from the vacuum canister than you would normally desire, since the vacuum from the loadomatic is inadaquate" So both mismatched combinations will get less advance, right? I know my carb has the spark control on it. Either way, I'm not too concerned. When I go to my 200, I want to get a NEW carb and stop wasting time with these ancient, warped, lousy carbs! If I don't go back to the 2 bbl, I'll probably get a new 1bbl webber as I've heard others here say they are much more reliable than the 1100, and cheaper than a pony carbs rebuild. I may see if webber makes a larger one barrel carb intended for the 250 that I can adapt to the 200. We'll see

S-man

 

[Anonymous]

Thor - Hey bud...

Well, we are describing 2 less than ideal situations. One is just worse than the other.

 

[cdherman]

Indeed, we said opposite things, and I am not 100% certain that I am correct. I have searched here, over at FTE, googled the whole net, read my 65 shop manual (which has a good loadomatic explaination, FYI), all without finding a source of info that seems 100% reliable. There has been mostly a "preponderance of opinions" that the loadomatic carb produces less vacuum that the later, ported vac carbs.

I have an older, loadomatic style dizzy, and I guess I could test each with my carter carb and see which gives the most advance under a given set of vacuum readings. But too lazy, and moreover, my 38 year old dizzy, compared to a newly remaned dual advance unit might not really tell us much.

If someone knows for certain, than speak up!! Wish we could scare up some old Ford mechanic or engineer that would know.

later...

 

[Anonymous]

Maybe I wrote my respsonse a little poorly. When I said "Exactly" I was agreeing with cdherman on this:

Attaching a loadomatic carb to a vac-mech dual advance dizzy will give you less advance from the vacuum canister than you would normally desire, since the vacuum from the loadomatic is inadaquate. You might be able to simply set the intial advance a little high and get by fine.

You will get less than desired advance, but this setup would be better than a post '68 carb matched to a pre '68 distributor. Sorry for the confusion.

 

[addo]

Assuming the current carb is just a little thirsty, not way busted, how much fuel can realistically expect to be saved in dollars?

 

[LEROY POLL]

HELLO EVERYONE.


.....THE LOAD A MATIC WILL WORK WITH ANY CARB. IT WORKS BEST WITH THE MATCHING CARB THAT WAS MADE FOR IT.

.....IF YOU HAVE THE LOAD-A-MATIC AND THE WRONG CARB, THEN ALL YOU WILL HAVE TO DO IS SWITCH TO THE MANIFOLD VACCUM SOURSE. THIS WILL HAVE SOME W.O.T. FLAT SPOTS BUT WITH 3/4'S OPEN THEIR IS NO NOTICIABLE DIFFERANCE.

.....THEIR MIGHT BE SOME PROBLEM IF YOU WERE HAULING SOMETHING AND WOULD BE PUTTING YOUR FOOT HEAVY INTO THE CARB. YOU WOULD BE GETTING ONLY THE TIME OF 6* OR 12* THAT YOU HAD SET=UP THE TIMING AT.

.....THIS CAN BE SMOOTHED OUT BY TAKING SOME SPRING PRESSURE OFF THE ADVANCE. I HAVE USED THIS SET-UP FOR YEARS. THE ONLY PROBLEM WAS CHANGING THE POINTS. WITH AN OLD DIST. TESTING MACHINE YOU CAN MAKE THE DIST. WORK SO WELL YOU CAN'T TELL IT WAS A LOAD-A-MATIC.


.....I HAVE TAKEN OLD FACLONS THAT WOULD NOT RUN WELL AT ALL.... BECAUSE IT HAD THE WRONG CARB....AND WRONG TIMING.. AND VERY POOR FUEL MILEAGE.. AND MADE THEM LIKE BRAND NEW.

.....AN EXAMPLE. MY FRIEND BOUGHT A 1962 FALCON TWO DOOR WITH A 170 3 SPD. MANUAL TRANNY. HE ONLY GOT 14.5 MILES PER GAL. IN TOWN AND JUST 15.4 ON THE ROAD. I LOOKED AT IT WITH A TIMING LIGHT AND IT WAS OFF BY 15*. I TOOK OFF THE ADV. AND NO CHANGE. MOVED THE TIMING BACK 15* TO 10* TO START WITH AND IT WOULD NOT RUN UNDER LOAD AT ALL. I CHANGED THE VACUUM ADV. TO THE MANIFOLD AND MOTOR WOULD RUN AT ABOUT 1200 RPM. WE THEN RESET CARB. BACK DOWN TO ABOUT 550 RPM'S AND AND CHECK THE TIMING AND IT WAS AT ABOUT 30*. WE TOOK OFF THE VACUUM AND CHECKED AGAIN AND HAD OUR 10*. WE DROVE THE CAR AND ALL THE PROBLEMS WERE GONE. MILEAGE WENT TO 19 IN TOWN AND 25.5 ON THE ROAD. HE HAD BOUGHT THE CAR FOR $500.00 FROM A GUY WHO WENT DOWN A BOUGHT A NEW 1970 MAV.

.....THIS GUY HAD TRADE IN A NINE YEAR OLD CAR FOR ANOTHER ONE JUST LIKE IT. THE ONLY PROBLEM WAS HE DID ALL THE WORK ON THE CAR HIMSELF AND DID NOT EVEN HAVE ONE BOOK ON THE 1962.

......I HAVE SEEN THIS AGAIN AND AGAIN. AND SOME PEOPLE WILL NOT LET YOU EVEN LOOK AT THEIR CAR. THEY SAY THEY ONLY LET THEIR MACH. WORK ON THEIR CAR!!!!

.....JACK YOUR POST IS RIGHT ON. THE ONLY PROBLEM I'VE SEEN ON THIS FORUM IS PEOPLE WON'T WORK A PROBLEM THROUGH. THEY JUST JUMP TO WHAT THEY THINK WILL WORK BEST. THIS SYSTEM WILL WORK AND WORK VERY WELL IF IT IS MATCHED TO THE CORRECT CARB, AND HAS NO VACCUM LEAKS.

LOTS OF LUCK EVERYONE....LOLE

LIVE IN GRACE

LEROY POLL

 

[CobraSix]

I don't really think you'll save that much in gas. Your car needs a certain amount of power to go 60MPH, power is based on air and fuel. You'll need a certain amount to go 60MPH. Going to a smaller carb isn't going to change that much.

Case and point. I get just as good of mileage with my Ausse with a 390 4V as I did with my 1100 so long as I don't have too much fun. I can easily get 26-27MPG with my 390, and the most I go out of my 1100 was 28MPG. Now I don't hav to drive like a grandma to get the mileage, just not like a banshee. When I drive it like I did for the first couple of months (with a big grin on my face), I only got 20-21MPG.

So, the only real way the 1100 will save you money is by forcing you to drive slower because it can't crank out as much HP potential.

Slade

 

[Anonymous]

So, the only real way the 1100 will save you money is by forcing you to drive slower because it can't crank out as much HP potential.

Slade

I agree with this to a point I know that the 2bbl was pouring raw gas down into the intake as the engine just can't breathe that well, even with the accelerator pump rod made as short as I could. I never used the choke with that carb as hitting the gas a few times flooded it. Think about it- the 2bbl intake has a hole twice the size of the 170.

I did an experiment- after driving on the freeway, I checked the plugs and they were clean. After driving around town they were all sooty- not like the 1 bbl. I got 14.6 mpg, both in town and on the freeway, tested separately, filling the tank in between. With the 1bbl, it averaged 17 and didn't foul the plugs!

I put the one barrel on today- leaks a bit since the housing is warped, but the car runs much better, and it still needs some fine tuning. I does not feel much slower than the 2bbl, either. The only thing I miss is the granada gas pedal and cable- I hate this stupid plastic falcon gas pedal that comes up from the floor!

Leroy,

So are you suggesting I pull my vacuum hose off the carb and fit it to the intake where my trans vac. line goes in, and that will give me better mileage?

 

[CobraSix]

Sounds like something isn't right. 14MPG? my worse was 17 in the city basically using all 4 barrells of my 390 at every stop light. Sounds like something may be off. Even with my 1V and 2.77, I got 25 MPG on the Highway...

Slade

 

[MustangSix]

Any carb that pours raw fuel into the intake is malfunctioning.

 

[cdherman]

Leroy -- I don't follow what you are trying to say.

Are you saying that the loadomatic carb setups (with spark control valve) produce MORE vacuum than a conventional ported vacuum source?

While that may be true, by mating a conventional carb with a loadomatic dizzy, you would then get too little advance, as the conventional carb would be giving less vacuum. By switching to manifold vacuum, you will not get one bit more advance under most conditions, except at idle, where you will get lots of advance (right when you need it least).

I am not saying you are wrong, but hooking up to manifold vacuum is not something usually recomended. And I don't see how it would rectifycarb mismatch. It might solve other timing problems, but I don't follow your post.

Please try again -- you seem to have good experience, so I am not discounting your ideas, just trying to get them straight.

 

[addo]

Doesn't the Load-O work backwards to conventional dual-advance? I mean, it uses vacuum to retard the ignition. Vacuum drops, it self-advances. Getting one's head around this aspect is part of the hurdle.

 

[LEROY POLL]

HELLO CD.

..... THE LOAD -A-MATIC HAS ONLY SPRINGS TO ADJUST THE ADVANCE. SO IT WILL WORK AGAINST THE MANIFOLD VACUUM.

.....STARTING AT THE UNDERSTANDING OF THE LO-A-MATIC AND SEEING HOW IT WORK WILL HELP YOU SEE HOW DIFFERENT IT WORKS AND HOW BACKWARD TO OUR NORMAL UNDERSTAND.

.....FIRST THE LO-A-MATIC WILL OVER ADVANCE AT IDLE. YOU CAN SEE AS MUCH AS 40* ADV. WITH THE VACUUM HOOKED UP. WITH THAT MUCH ADVANCE ALREADY IN.... YOU REALY DON'T NEED ANY MORE ADV. WHAT YOU HAVE IS A MANIFOLD PRESSURE OF AROUND -20 POUND OF VACUUM GIVING FULL ADVANCE. WHEN YOU START TO MOVE FORWARD THE MANIFOLD PRESSURE WILL DROP TO AROUND -8 TO -10 PDS OF VACUUM. THIS WILL DROP THE ADV. TO ABOUT 45 % OF FULL ADV.

..... WHAT HAS HAPPENED INSIDE THE LO-A-MATIC IS THAT THE SPRING THAT HOLD AGAINST THE MANIFOLD PRESSURE HAVE PULLED THE ADV. BACK TO ABOUT 24*.

.....THE LOAD-A-MATIC GIVE ABOUT 30*BUILT IN MAX ADVANCE. IF YOU START WITH 10* OF ADV. ADD 30* WITH VACUUM YOU GET 40* ADV. LOOKING AT A DORP OF 55% OF MANIFOLD PRESSURE.... YOU WILL SEE ABOUT 16* DROP IN ADV. YOUR TOTAL ADV. AT THIS POINT WOULD BE 24* ADV....OR 10* + 14* =24*

.....AS YOU MANIFOLD PRESSURE BUILDS BACK TO IT'S MAX PRESSURE THE ADV. WILL BUILD BACK TOWARDS THE 40* YOU HAD AT IDLE. BUT UNDER A LOAD YOU CAN'T GET BACK TO THE -20 PDS YOU HAD AT IDLE. SO IF YOU CAN GET -17 PDS. OF VACUUM YOU WILL SEE ABOUT 85% OF FULL ADV. THIS WILL GIVE ABOUT 35.5* OF ADV... OR 10* + 25.5* = 35.5*.

.....MANIFOLD VACUUM CAN GET AS HIGH AS -29 PDS WITH YOU GOING DOWN HILL AND MOTOR IS HOLDING BACK THE CAR. BUT THE 30* MAX ADVANCE BUILT INTO THE LOAD-A-MATIC WILL KEEP THE ADV. FROM GOING TO 55* OR MORE. YOU CAN FILE THE STOPS TO GET ABOUT 4 MORE DEGREES. I HAVE DONE THIS BUT IT DIDN'T SEEM TO GIVE ANY DIFFERANCE AT ALL.

.....THE VACUUM IS MUCH HIGHER ON A 1100 CARB. BECAUSE IT USES TWO VACUUMS. PORT AND MANIFOLD. THEY DO NOT WORK TOGETHER. THEY WORK INDEPENDENT OF EACH OTHER. THE LITTLE VACUUM SWITCH ON THE 1100 CARB. IS SET UP TO PULL THE SWITCH SHUT WITH HIGH MANIFOLD VACUUM AND OPEN WHEN THE MANIFOLD VACUUM FALL TOO LOW. IT IS THEN THE SWITCH OPEN AND THE DIST. SEES THE PORT VACUUM AT WHICH POINT THE PORT VACUUM WOULD BE BUILDING TO A HIGHER POINT. AS THE MANIFOLD VACUUM COME BACK TO A STRONGER POINT IT SHUT OFF THE PORT VACUUM AND SWITCHES BACK TO THE BUILDING MANIFOLD VACUUM. THIS ACTION SWITCH IS WHAT MAKES THE ADVANCE SEE MORE THAN THE 10* SETUP ADV. WITHOUT THAT SWITCH YOU CAN GET SOME LOWER ADV. WHEN STARTING OUT.

.....AS WAS SAID BEFORE WITHOUT THE SWITCHING INSIDE THE CARB. TO MANIFOLD PRESSURE THE LOAD-A-MATIC WILL NOT WORK CORRECTLY. SO IF YOU NEED -20 PDS OF VACUUM TO MAKE THE LOAD-A-MATIC WORK..... IT WON'T WORK WELL AT ALL WITH A PORT VACUUM ADVANCE.

.....AGAIN THE LOAD-A-MATIC WORK BY OVER ADVANCING. THE LOAD OF THE MOTOR WILL SET THE ADVANCE LEVEL. YOUR FOOT REALY IS THE THING THAT SETS THE ADVANCE. THE HEAVIER THE FOOT THE LESS ADVANCE. THIS DESIGN WILL GIVE THE BEST FUEL ECONOMY. MOST MOTORS WILL RUN AT HIGH MANIFOLD PRESSURE AND WILL BE GIVING THE BEST ADV.

....I MIGHT JUST SAY HERE THAT THE DIFFERANCES IN ADVANCE UNDER POWER IS NOT MUCH TO WORRY ABOUT. FOR ALL OUT RACING YOU JUST WOULDN'T YOU A LOAD-A-MATIC. BUT IF YOU WANT THE MOTOR TO WORK IT'S BEST AT ALL TIMES YOU ARE DRIVING YOU WOULD WANT THE LOAD-A-MATIC.

....AS OTHERS HAVE SAID...... "MOST OF THE PROBLEMS WITH THIS DIST. IS THE CARB...!!!"

.....MOST OF ALL OF THIS IS IN A BOOK CALLED...FIX YOUR FORD. IF YOU SEE BUY IT.

LOTS OF LUCK....LOL

LIVE IN GRACE

LEROY POLL

 

[LEROY POLL]

HELLO CDHERMAN

.....CD IS THAT ANY CLEARER? DID YOU READ THE LAST POST?


.....CD I WAS WONDERING....DO YOU STILL HAVE A LOAD-A-MATIC ON YOUR 240?

LIVE IN GRACE

LEROY POLL

 

[cdherman]

For the record, having read and re-read the prior post, there are a number of correct points in there. But, it is absolutely wrong that the loadomatic switches between ported and manifold vacuum. The spark advance valve switches between PORTED (just ABOVE the throttle plate) and VENTURI vacuum.

I once again have tried to learn even more about loadomatic systems and still don't know for sure what is right. If you hook up a loadomatic dizzy to a manifold vacuum source (assuming you have a stock cam producing the usual sort of vacuum curves), you will get trendous advance at idle. As Leroy correctly notes, this will fall as you open the throttle. As you open the throttle fully, you will dissapate all the vacuum, and your dizzy will allow the spark to return to whatever it was before vacuum was hooked up. Exactly the opposite of what you want.

As stated above, the loadomatic system used the venturi vacuum, present in the venturi of the carb, and highest at high CFM air flow, to give advance while "under load" when the vacuum falls. Thus the name.

I do not think there is any good way to use a loadomatic distributor with a non-loadomatic carb. You need mechanical advance. Period.

Addo -- indeed, the loadomatic can advance the spark, or at least keep it steady in states of falling MANIFOLD or PORTED vacuum, and in that sense, it is opposite to conventional dual (vac/mech) setups. But it does so by switching to a different source of vacuum (Venturi).

Try this link for a real nice piece about the history and theory of spark advance, as well as some insight into ford loadomatic systems.

http://www.btc-bci.com/~billben/navarro.htm

 

[Anonymous]

I guess this has opened up an interesting discussion about loadamatic distributors- but I don't have one

S-man