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swapping over to single carb on 57 eldorado ?

Started by paul57, November 13, 2010, 11:34:33 AM

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paul57

going to swap over the twin carter set up on my 57 eldorado for a single carb ,  i just cant cope with the fuel consumption at 5mpg !  :o
was thinking of using one of the carters i already have , but what jet sizes will i need to fit  , if any ?
or would i be better off getting a 600 holly or edelbrock with jets to suit ?

p murphy

uk ..
but its what i've always wanted and this time its a keeper , honest !

1957 cadillac eldorado seville . turning fuel into vapours ...

pmurphy

Dave Shepherd

An out of the box 600 Edelbrock with an electric choke should do it, of course most important is the trans tv rod , must be hooked up and adjusted, look at this issue before putting this carb on. You will need to fabricate new fuel line set up of course.  Maybe you find an oe style Carter from a 57 or 58.

Mike Josephic CLC #3877

Five miles per gallon?

I'm very surprised that's all the better your car will do.  My '55 Eldo with dual
quads gets 15 mpg on the highway.

Before you go through this drastic swap, have you checked all of the normal engine
items that can contribute to poor mileage?  The basics like tune up items, vacuum leaks,
exhaust restrictions, fuel problems, carb issues, etc.

Mike
1955 Cadillac Eldorado
1973 Cadillac Eldorado
1995 Cadillac Seville
2004 Escalade
1997 GMC Suburban 4X4, 454 engine, 3/4 ton
custom built by Santa Fe in Evansville, IN
2011 Buick Lucerne CX
-------------------------------------
CLCMRC Museum Benefactor #38
Past: VP International Affiliates, Museum Board Director, President / Director Pittsburgh Region

The Tassie Devil(le)

G'day Paul,

I am with Mike on this one.

There has to be something drastically wrong with your total system.

A Multi-carb setup, correctly adjusted shouldn't be any more fuel consumptive than a single carb setup.

The thing about Multi Carbs, is that they don't have to be opened up as much as a single carb to gain the same performance, therefore, the same amount of fuel is being used to gain the same performance.

BUT, when putting the foot down, the Dual Carbs will give better performance (Read as more fuel used as well).

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Roger Zimmermann

Well, I have a different opinion and experience. The dual set-up uses more fuel than a single 4 barrel. Why? the air speed at each carb is too low to have a good atomization of the fuel, therefore there is a lot of waste.
My '56 de Ville with 1 carb is using 13l/100 km when the Brougham (OK, it's 250 kg heavier too) is using 18 l/100 km in the same conditions. I don't even talk about the Biarritz; when open, a car is using much more fuel as it's as aerodynamic as a barn's door.

Roger
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Quentin Hall Australia

I am amazed to see all the 57 questions popping up. Are 57s the new 59s?
In any event I just bought two rebuild kits for my 57 Biarrrtiz dual quads currently off the car. The car has had the dual quads removed and a single carb put on sometime in it's life. 5MPG !!!???? Ouch.  I  had a friend with a 57E Brougham who said 8MPG was on a very good day. Hence the duals may just stay on the shelf to look at . . . . My 59 Biarritz with triples seemed pretty good but I never botherd to do a MPG . . . . some things are perhaps best left unknown.

paul57

thanks for the replies , everything is as it should be , and there is certainly nothing as you put it ' drastically wrong ' with the system  ;) , have spoke to probably twenty people who have in the past or still run caddys with the twin carters on . 5mpg seems to be the average on these later 50's cads , you can squeeze out 10-13 mpg on a steady 50mph run but thats it !  :o .
maybe the reason that a lot of 57 eldos do not have their twins still with them when they crop up for sale ?  sorry , but have ran a few cars in the past with twin carbs , they will always use a lot more fuel than a single carb set up no matter how its driven ...
jusy out of interest , what do you guys who run '57's with a single carb average ?  seeing as its roughly $8 a gallon over this side of the pond the swap is being done to see if i can afford to keep it , i certainly cant afford to run it with the twins on , as i like to use my cars every week of the year where possible .
still need some jet sizes or info on whether just one carter will swap straight in ?

but its what i've always wanted and this time its a keeper , honest !

1957 cadillac eldorado seville . turning fuel into vapours ...

pmurphy

Dave Shepherd

I am working on a friends 57 Seville with one Carter AFB, runs great, gets 10-12.  The problem with the 2x4's back then was they ran off the primarys of both carbs even at part throttle, todays set ups and manifolds are running off the primary of the rear carb, using progressive linkage.  There is probably  way to do this with the oe 57 set up, but you must look inside the manifold to check the runners first.

J Kjerrulf

I hear what you say Paul but something is wrong.

I drive my "all original" 1957 dual quad Carter Eldo all year around. During warm summers and arctic winters she has often been my familys single working car.
Speaking from my own experience I have only been close to the poor mpg mentioned during my frozen lake Ice Racing or when something is very, very broken. (will add link to "57Eldo Ice racing" later! ;D)

I must also make my opinion clear that I don't think it is fair to compair fuel consumption of a 285hp 1956 with a heavier and gadget-drowned 1957 325hp Eldorado!
The 1956 may be a better car in many ways but note the significant difference in hp!
Yes, the 1957 dual setup may be thirsty compared to a single carb(and to pre 57 cars) but not as low as 5mpg - or 8.

I have driven around 30 000 km with this car with these carbs.
My best is 14L/100km (with A/C off) on a steady 45 mph, this year I guess my summer average is around 16,5L/100km (some 16-17mpg, A/C still off) on hwy. 12-15mpg in winter with cold starts/city drivin. Worse yes,  but not as bad as 8 mpg.. Something is obviously wrong. If it is my car I don't want it fixed.

Paul, are you really sure the Eldo carbs/Eldo distributor/Eldo transmission are correct and working OK in your car? ???
Have you had your carbs checked by a pro?

During my first miles I had some fuel consumption related problems sorted:
-A functional factory fuel return line! Could be an indirect source of abnormal consumption - duals consumes what you give them, hardly no upper limit!
-Engine: A non-functional heatriser causes heavy wear on the 57 cylinder heads (if you're lucky) and increased fuel consumption follows.
-Brakes: Car should brake and stop only when needed. My brake pedal "return spring" was broken, did increase mpg a lot.
-TVrod adjustment, myself I can't hear the shift between 3rd & 4th. Car will consume more on hwy in 3rd...
-Vacuum leaks appear even for the best mechanic on the best of cars. Duals are more sensitive!
-Wider radial tires with lower profile affects fuel consumption negatively and combined with the duals factory gear ratio they will add even more difference compared to the fuel consumption of a single 1957 Carb. I ride 8.90 today, works for me.

I rebuilt my carbs myself. I left the final adjustment to an ex dragracing champ after I have checked the internal parts were correct.

Perhaps it's a good idea for you Paul to swap to a single carb, but don't be disappointed if you still have a high fuel consumption afterwards. An out of the box Edelbrock will at best give you 10mpg, worse than a functioning pair of dual Carter AFB and uglier. A lot uglier.

J Kjerrulf
/J Kjerrulf
Eldorado Seville 1957

The Tassie Devil(le)

Oh dear, I assumed that the Dual Carby setup on these engines was of the Progressive Linkage style.

I take back not everything I said in my previous post, but fuel consumption does have a lot to do with the right foot.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

bcroe

A couple things to check are the timing chain, and the rear axle ratio.  I run 2.41 axle here for economy, it really helps at the expense of some off-the-line performance.  A powerful electronic ignition & a really low restriction exhaust will have some effect.  Bruce Roe

paul57

mmm , 57 eldo ice racing , now that i've got too see ! 
interesting that you seem to be getting really above average mpg on your eldo according to info from the people i have spoken to , i would leave it as it is  ;D
i do have radials fitted on the front , 235/75/15 with 820 bias plys on the rear ,
car does not have a heat riser fitted ,
it is fitted with an electronic ign ,
definately changes up and down the box fine with no problems ,
brakes have just been renewed front and rear , cyls and shoes .


i did have a problem with the carbs when i got the car just over a year ago , the acc pump rods were a bit  ' sticky ' , i must confess , it is a job that i have not done as yet , and the car does hesitate for a brief second when accelerator is pressed , could that be the cause i wonder ???
cant think of anything else that would cause it to give me the 5mpg  i have been experiencing ? 
and no , i don't drive with a lead foot .... ;D
but its what i've always wanted and this time its a keeper , honest !

1957 cadillac eldorado seville . turning fuel into vapours ...

pmurphy

Roger Zimmermann

I cannot answer to your questions; however, a bad acc pump will have no effect on the mileage. You may have to check if your odometer is recording the driven distance; it may be totally off. An error of 5% is acceptable.
You have a dangerous car with bias ply tires at the rear and radial at the front. The behavior of the tire systems is very different; you may lost control of your car driving that way.

Roger
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

paul57

roger , the car handles like a dream as it is at all speeds , cornering etc , you only experience problems if you mix tyres on the same axle ,or drive like a pr*t !  in fact , car has just been in for its annual safety check .  and i think speedo doesnt really come into it do you .... ::)
but its what i've always wanted and this time its a keeper , honest !

1957 cadillac eldorado seville . turning fuel into vapours ...

pmurphy

Roger Zimmermann

Well, if you get catch in Switzerland with a mix bias-ply and radial tires, you are not allowed to drive further.

Roger
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

paul57

good job i dont live in switzerland then isn't it .... ;D
but its what i've always wanted and this time its a keeper , honest !

1957 cadillac eldorado seville . turning fuel into vapours ...

pmurphy

The Tassie Devil(le)

Sorry, but I agree with Roger on the tyre situation.   If putting a pair of Radials on the vehicle, they must go on the rear first.

But, an incorrect Speedo will have implications on mileage figures.   Seeing that these vehicles have a built-in +10% over-reading, when calculating the amount used for the distance travelled, you will be dividing the actual amount of fuel used against an actual further distance driven, and therefore the result will show a better MPG than if the correct distance was used.

Bruce.  >:D



'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

bcroe

Actually, a speedometer/odometer that reads high (nearly universal in USA), will tend to make gas mileage look better than it is.  One of the things I do is recalibrate the speedo on all my cars to get correct info.  Bruce Roe

kgray39011

The Cadillac Dual Quad Manifold has the connection between the front and rear carbs. It is posible to run off one carb I suppose. I know Edelbrock has replacement carbs (model 1803 or 1804) and progressive linkage (7094). I find it hard to believe that you are only getting 5 MPG unless you are having a mixture problem. I would pull the spark plugs and inspect for a nice tan color on the elements. If you have black plugs, you are running way too rich! If your secondarys are not sealing properly, you will have to really open up your idle screws to compensate for the excessive air. I would check for the seal on the secondaries. Tuning Dual carbs is an art.

I know that a tri-power is better on gas but they can have issues tuning also.
Kenneth P. Gray - 2013 BMW 328i xDrive Sport Imperial Blue
Christine (Wife) - 2010 Cadillac SRX Performance Package White Diamond
Looking for a 1949 Coupe Driver

kgray39011

Have you looked at your vacuum advance on your distributor? If your vacuum advance is not working it will reduce your mileage 3-4 MPG easy. always set the timing with the advance disconected, then hook in your vacuum advance back in and you should see the timing jump up a few points. If it does not, get it fixed.

I thought I would leave a couple of other notes on carburetion. If your float levels are set too high, the engine will run rich. Air Fuel Ratio Characteristics :o:

5 RICH BURN LIMIT: Combustion is weak/erratic.

6-9 EXTREMELY RICH: Black smoke and low power.

10-11 VERY RICH: Some supercharged engines run in this range at full power as a
means of controlling detonation.

12-13 RICH: Best power A/F: Un-supercharged WOT.

14-15 CHEMICALLY IDEAL: At 14.6 the A/F is at the theoretical ideal ratio with no
excess fuel or oxygen after combustion. Good A/F for part
throttle cruise and light to moderate acceleration.

16-17 LEAN: Best economy A/F ratio. Borderline for part throttle
drivability (worse than borderline if EGR is used).

18-19 VERY LEAN: Usual lean limit (Driveability).

20-25 LEAN BURN LIMIT: Varies with engine and system.

Even though engines will run anywhere between 5 and 25 A/F, the usual target values for an unsupercharged engine are a fairly narrow range (Figure 1). A/F is about 12.5 for the WOT and 14.0-15.5 at part-throttle cruise. An intermediate value of about 13.5-14.0 is usually used for mid-range power (non-WOT acceleration).
Kenneth P. Gray - 2013 BMW 328i xDrive Sport Imperial Blue
Christine (Wife) - 2010 Cadillac SRX Performance Package White Diamond
Looking for a 1949 Coupe Driver