Gas mileage 1958 Cadillac FLower Car

Just bought a 1958 Cadillac Eureka Flower Car and getting to know it. Excuse if I am asking newbie questions, but with procars, I am a newbie!

We own several 1958 Cadillacs so I am familiar with the basic breed.

On the road, I get about 15 mpg with my other cars, but the Eureka is getting about 6 MPG. is this usual or do I have a problem?
 
As I recall our former Fort Wright (KY) 1973 S&S-Cadillac High Top Ambulance (that Bruce-B has now) got an average if 8 MPG on a long trip from the PCS Convention in Minneapolis to San Diego in the mid-90's when we first bought it. This was at legal freeway speed limits with the A/C on all the way in the middle of Summer. Later, fine tuning and some exhaust work, it increased to about 10-11 on local trips to events here throughout Southern CA.

Our car was probably somewhat heavier than yours ("Tipping the Toledo's" as Evan Butchers would say at at 8,000 lbs) with definately more wind resistance, so your's should get better with some work. MM
 
Assuming that this car has the original engine, you might be able to get better fuel mileage by fine tuning the engine, and possibly a carburetor rebuild. The problem with todays fuels, they contain less BTU's per gallon than the premium fuel that was available when the car was first produced. If you have access to fuel that doesn't contain the mandated 10% ethanol content, that will boost your mileage by about 10 - 15%. A gallon of gasoline contains 114.000 BTU (British Thermal Units) of energy, and ethanol has 76,100 BTU's per gallon. If you add 10% ethanol to the gasoline, to stretch the gasoline, you are actually degrading the pure gasoline, hence less power your engine can make, and the more fuel that is required to move the vehicle. Inflating your tires to the highest amount per the labeling on the tire sidewall will also reduce the rolling friction and increase your mileage. Also, driving your car on a damp day will also help, as the moisture in the air as it enters the combustion chamber will turn to steam, however, that is a discussion for another time...
 
my experience is if she is running right 10 11 is possible. but a car that has been sitting is going to take a bit to clean it out. you ask how to tune it you, get a different response from everyone. treat like you do the rest. it will run like the rest. get a little less mileage. you can't subtract wight and that eurekas has at least 100 lb of lead in it. along with the rest of the different construction. you got to love the 58 year though a vary classy body.
 
Six MPG seems a bit low but a 58 Caddie sedan would only do 12 mpg around town and you hoped for 16 mpg on the road. The weight and wind resistance of the flower car or for that matter any pro car just kills mileage When we got he first gas crunch I was driving a 76 Plymouth 440 Police cruiser and it got 12 mpg did not matter if you were on it or off it 12 mpg. The early 50s Cadillacs were noted for their good miles with the early Hydramatics but with the introduction of "Jetaway" in 1956 the gas mileage did just that. Remember gas was in the 25 to 35 cent range then so nobody cared. I would not spend a lot of $$$ trying to bring the miles up I don't think you will get a return on the investment. Three recomendations air the tires up say 35lbs,check air cleaner make sure the element is clean,when warm make sure the choke is completely open oh yeah and make sure the exhaust heat riser valve is free and not stuck closed. All of that and you may hit eight mpg
 
Six MPG seems a bit low but a 58 Caddie sedan would only do 12 mpg around town and you hoped for 16 mpg on the road. The weight and wind resistance of the flower car or for that matter any pro car just kills mileage When we got he first gas crunch I was driving a 76 Plymouth 440 Police cruiser and it got 12 mpg did not matter if you were on it or off it 12 mpg. The early 50s Cadillacs were noted for their good miles with the early Hydramatics but with the introduction of "Jetaway" in 1956 the gas mileage did just that. Remember gas was in the 25 to 35 cent range then so nobody cared. I would not spend a lot of $$$ trying to bring the miles up I don't think you will get a return on the investment. Three recomendations air the tires up say 35lbs,check air cleaner make sure the element is clean,when warm make sure the choke is completely open oh yeah and make sure the exhaust heat riser valve is free and not stuck closed. All of that and you may hit eight mpg
 
I think I have a carburetor problem. Starts well, but then quits until warm. Recently has been stalling when I slow down for a light.

We have two other 1958s, an Eldorado Seville and an Eldorado Biarritz convertible. These have the same engine (365 ci) and they get about 15mpg on the highway.

The Flower Car is heavier and has a lower ratio final drive, 3.77, so I would expect less mileage. The 58 sedans had 2.94, the Eldorados had 3.36.

I surmise that most Cadillacs were built for highway driving more than around town, so a lower ration final drive was better. But since flower cars were built for slow driving in funerals, a higher drive was better.

I have electronic ignition, but otherwise stock 1958 engine. I'll check timing, advance, as well. Also possible I have a vacuum leak.

The mileage is not a huge concern to me, I just want to be sure it is running as it should.
 
a good turn up requires a a check of all vacuum fittings. but really it's most lily sitting problems with the cab and poor quality fuel. the dieing says to me choke not setting properly. the CC ran lower final drive gears not only because they ran at slower speeds they also used a bigger tires on it then the standard caddy. the 890x15 were 8 ply with a 31 in dimanter.
 
a good turn up requires a a check of all vacuum fittings. but really it's most lily sitting problems with the cab and poor quality fuel. the dieing says to me choke not setting properly. the CC ran lower final drive gears not only because they ran at slower speeds they also used a bigger tires on it then the standard caddy. the 890x15 were 8 ply with a 31 in dimanter.

I think the final drive is 3.77 - the '58 Eldos used 3.37 and the regular car used 3.07 - Good point on the tire size. They are huge! I wonder if the larger diameter offset much of the lower final drive?

I am getting a new set of Diamondback Radials 265/75 - 15R 2 3/8" 6 ply whitewalls. Tires that are on it are out of round from sitting so long.

I have the carburetor off and am checking for trash/gum. The previous owner only drove it 234 miles since 2005. There is no fuel filter so I am installing a glass bowl type. Probably an electric fuel pump at the tank.

I will check for vacuum leaks. Good idea. Should not be too hard because the wipers are electric and the heater/ac has been replaced with Vintage Air.
 
Six MPG seems a bit low but a 58 Caddie sedan would only do 12 mpg around town and you hoped for 16 mpg on the road. The weight and wind resistance of the flower car or for that matter any pro car just kills mileage When we got he first gas crunch I was driving a 76 Plymouth 440 Police cruiser and it got 12 mpg did not matter if you were on it or off it 12 mpg. The early 50s Cadillacs were noted for their good miles with the early Hydramatics but with the introduction of "Jetaway" in 1956 the gas mileage did just that. Remember gas was in the 25 to 35 cent range then so nobody cared. I would not spend a lot of $$$ trying to bring the miles up I don't think you will get a return on the investment. Three recomendations air the tires up say 35lbs,check air cleaner make sure the element is clean,when warm make sure the choke is completely open oh yeah and make sure the exhaust heat riser valve is free and not stuck closed. All of that and you may hit eight mpg

I would like to ask what years did they run the "jet away" trans from when to when?
 
a lot of stuff sounds good but think about it. the car ran this long with out a electric pump. hide a in-line filter in a easy accessible spot along the frame. it's not seen and no splices under the hood. it will protect both the fuel pump and the the carb from what ever it can. I have found a electric pump with out a regulator can over power the needle valve and cause more trouble then it saves. you are not going cost to cost drag racing the car. you just want it to drive nice. it did in 58 it can today just like it did in 58. you feel the fule pump is weak replacing the diaphragm with one of newer materials is a simple task.
one of the biggest mistakes we all make is changing to many things at once to fix one problem. you never know if you did not fix it or created a different one.

let me know when you change those tires I'll take pay the fright and what ever on the old ones I have a few just sitting around that can use them. the 58 should be able to use the 265's they are a lot wider tire then original so clearance in the rear on the 60 and 70's car is a problem. but they are the same size around.

I have been told that the jetaway ended in 63. I have no Ida when it started.
 
I think the final drive is 3.77 - the '58 Eldos used 3.37 and the regular car used 3.07 - Good point on the tire size. They are huge! I wonder if the larger diameter offset much of the lower final drive?

I am getting a new set of Diamondback Radials 265/75 - 15R 2 3/8" 6 ply whitewalls. Tires that are on it are out of round from sitting so long.

I have the carburetor off and am checking for trash/gum. The previous owner only drove it 234 miles since 2005. There is no fuel filter so I am installing a glass bowl type. Probably an electric fuel pump at the tank.

I will check for vacuum leaks. Good idea. Should not be too hard because the wipers are electric and the heater/ac has been replaced with Vintage Air.

Only 234 miles in almost 9 years? That is sad. I couldn't even imagine why someone would even own a car if they were not going to drive it. Im glad it went to a home that is going to drive it instead of let it sit in the garage. The first think I thought of was a vacuum leak too.
As for your rear end gears, I would love mine to be that high. My 49 S&S has 472 gears!
 
Took the carb off and disassembled it. Very clean. No swarf, no gluck. Beginning to think it is an ignition problem.

Car is running poorly, especially when hot. Thought it might be vapor lock, but it does not quit.

Beginning to suspect the electronic ignition. If the module gets flaky it can cause misfiring. Overheating can bring this on.

Being an unfamiliar car I may be giving it more gas to compensate, hence the poor mileage. I plan to put the carb back on today, and do some module testing. Maybe replace the old Mallory with a new Pertronix Ignitor and Flamethrower coil.

Will keep you all advised.
 
Ed, Can '55, '57 and '60 also take the 265/75 15s instead of the 235s?

let me know when you change those tires I'll take pay the fright and what ever on the old ones I have a few just sitting around that can use them. the 58 should be able to use the 265's they are a lot wider tire then original so clearance in the rear on the 60 and 70's car is a problem. but they are the same size around.

I have been told that the jetaway ended in 63. I have no Ida when it started.[/QUOTE]
 
Ed, Can '55, '57 and '60 also take the 265/75 15s instead of the 235s?

let me know when you change those tires I'll take pay the fright and what ever on the old ones I have a few just sitting around that can use them. the 58 should be able to use the 265's they are a lot wider tire then original so clearance in the rear on the 60 and 70's car is a problem. but they are the same size around.
[/QUOTE]

Be happy to do so. These are good looking tires. I really thought they were bias ply when I first saw them, but they are out-of-round the vibration sets in at about 45mph and goes away at about 65mph.

I would guess they would fit ok. The front end of the flower car is the same as any other 1958 Cadillac, I think. They are about 10 years old, but did originally come from Diamondback.
 
the 265x15 are around 9 or 10 inches wide. they of a load range that is correct and a hight that is correct but in reality they are about 6 inched wider then the original tire. you best bet is to go down to a tire shop or junk yard and pick up a used one and see. here is a compression for you the 235s are in the 8 inch wide range. yes all of those tires are mounted and at proper inflation. the 58 is the spier out of the 58 I'm working on the 69 was the spare out of Paul's MM. all most refreshing to see even back them every time they made a run the tires got smaller. a new 235 is smaller yet
 

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Just to clarify, I am not interested in the tires, just asking if the 265s also work under '55, '57 and '60

Thank you for clearing that up. They look like they would fit. Front suspension appears the same on the flower car (86 chassis) as on the standard 58 (62
Chassis)

Sure would NOT fit on the back of my 1959!!!
 
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