1956 Cadillac 365 cutting out going up a grade

[Pasomike]

Hello,

This past weekend i took my car to my first concourse show. the car drove great, aside from the gas mileage. on my way home how ever we have to go up whats called the cuesta grade.
the car did not like this much, i did expect it to heat up a little more then normal which it did then cooled off when i got over the grade, but the car seemed to misfire or cut out a little going up the hill from time to time, has any one had this happen, it runs fine but seems like the load of going up the grade was a little much and it would kinda feel like it would cut and sputter a little bit.
i was a little worried about making it but has the kids and wife and pushed it and it did make it over the hill.

Any help like always is greatly appreciated.
over all driving over 100 miles with the car went great.

[walt chomosh #23510]

Mike,
  One day I pulled out of my garage and as I "gave her gas" to accelerate down the street it fell on her nose! (1955 CDV) I immediately returned to my garage and reviewed my shop manual. (Rochester 4GC carb) It told me that the power circuit was the problem. I cleaned the carb thoroughly and PRESTO...problem fixed!...sure wish all my fixes went that way!....don't ask me about some "fixes" that took me years to solve....walt...tulsa,ok....(BTW,be sure your vacuum advance is functioning properly,that can kill fuel millage)

[Caddy Wizard]

1956 running poorly going uphill in the heat?  Been there, done that.  Carb is starving for gas due to vapor formation in fuel lines.  If hot enough, it will vapor lock.  Best solution I have found is to remove fuel pump push rod and install a very robust electric pusher pump near the fuel tank.  Like an Edelbrock pump that has a built-in fuel pressure regulator.  See my postings on this elsewhere on the Forum...

[dplotkin]

You know, I scratch my head over all the electric fuel pump solutions pursued here and on other old car forums and discussions. I have a 56 Fleetwood and 7 other old cars from a 60 Buick to a 68 New Yorker and none have electric pumps and all climb hills as designed. I refuse to believe that this was a solution to a problem that escaped all those automotive engineers of the 1950's. Cadillac's climbed long, steep grades then and mine will today...with its stock fuel pump.

Now I hear many of you saying..."yeah but fuel back then was better, today it has alcohol that gasses easier in the heat. Perhaps. But that has not been my experience.

The 1956 Cadillac is a whopper. Its very heavy. And its 365 V8 makes 285 HP gross, which is more like 195 net. So say 200HP pushing a very heavy car up hill with highway gears, the car was working up a sweat. Cadillac says the needle can go and remain at 3/4 to hot and still be considered normal. If it didn't boil over it didn't overheat. Read the magazine road tests from the day, no one said these were fast. I let my Fleetwood take her time on big hills. At 61 years of age why should she be in any hurry?

Lastly, as you climb air pressure dropped and throws the mixture out of whack adding insult to injury. Check to see your timing is not too far retarded. Vapor lock is real, I don't deny it, and I agree a electric pump can all but rule that out. Remember, a Cadillac is the car of cars. Cadillac did not build cars that cannot climb hills without vapor lock.

Dan

[J. Gomez]

Michael,

That hill up in San Luis Obispo on the 101 is around 1500ft elevation if I recall. Most likely going up the hill you will need to press a bit harder on the gas possible going to ¾ throttle opening the secondary sets.

The symptom you experience could well be a combination of;

Fuel starvation due to infamous “vapor lock” with the Ethanol blend fuel when engine temp increases.
(Ambient temps around the engine can be in the 200 plus range while idling and the fuel pump and fuel line to the carb do take the blunt of that heat.)

Weak fuel pump not keeping up with demand when the secondary are open.

Carburetor problems or possible timing (vacuum advance) issues when going uphill, vacuum drops when throttle opens and retards timing, this would also cause an increase of engine temp.

Since in normal driving conditions you had no problems per your post on your 100 miles trip, I would take a wild guess your issues could be either one or a combination of problems above.

I recall there was another member in Southern Cal a few years back that had similar symptoms going up Cajon Pass up on I15 as you during the summer, not sure if he did any fixes or alternative work on his side.

Good luck..!

[J. Gomez]

You know, I scratch my head over all the electric fuel pump solutions pursued here and on other old car forums and discussions.
Dan

I’ve installed an electric fuel pump on my ’56 but I done a totally different arrangement for it from other layouts/setups I have seen/hear here and on other forums.

I have had no time to test the full functionality of my setup outside from a few minutes running at idle as other projects home/ work are taking a toll on my time to get back to my project.

I still need to get other things done carb adjustment, timing adjustment, etc. before I can fully test the setup when she is ready for a road test.

[Jeff Rosansky CLC #28373]

I know what you mean.  I have exactly 1 mile on the 55. There is so much more to do I don't even know where to start.
Jeff

[Caddy Wizard]

You know, I scratch my head over all the electric fuel pump solutions pursued here and on other old car forums and discussions. I have a 56 Fleetwood and 7 other old cars from a 60 Buick to a 68 New Yorker and none have electric pumps and all climb hills as designed. I refuse to believe that this was a solution to a problem that escaped all those automotive engineers of the 1950's. Cadillac's climbed long, steep grades then and mine will today...with its stock fuel pump.


Dan

I have driven a 1949-1956 Cadillac about 40% of my days over the last 30 years, as a daily driver in the heat of Atlanta.  Whether it is because of gasahol fuel (which I believe is at least half of the cause), I have experienced vapor lock and vapor "lean out" many times.  Granted, it only happens a small percentage of the time.  But if you use a car to go to work every day and then to run errands and whatnot, you end up driving the car something like 100-150 times per month.  If the car vapor locks (or stalls out going up hill due to vapor lean out depriving the carb of sufficient gasoline) just 1% of the time, that is a breakdown of once or twice per month in the heat of the summer.  That is what I often would experience, especially with 56 models.  49-51 models don't give me nearly as much trouble.  55s are a little more prone to issues, but not as bad as the hot running 56s.

Yes, vapor lock and related performance issues are real.  Yes, they drive me crazy.  Yes, installing a stout electric fuel pump is the best thing I ever did on my 56 Fleetwood...

[Jeff Rosansky CLC #28373]

It will also run hotter when lean (until you are lean of peak). Running hotter causes it to be hotter (of course) which promotes vapor lock-a spiraling issue.
Some of your extra heat going up the hill was because it was working harder. But some was probably because you are too lean.
My 70 was running not as nice last week and when shut off and restarted such as getting gas, the temp light was on which is very rare-but it stayed on for a minute or so which is very rare. When got home found power brake checkvalve broken causing it to run lean. Replaced and no more temp light--well, for now that is.
Jeff

[cadman56]

Several thoughts here:
1.  You mention in your post about poor gas mileage.  This leads me to think you might want to go back to basics for tuning it.  I use a vacuum gauge to set the carb and timing.  Hook it up to the metal line from the intake manifold and no where else. 
2.  I always ran 91 octane w/ethanol and never had problems with running out of fuel.  No, I don't have hills like you around central kansas but I do have lots of open space to put the pedal all the way down and hold it there as the car winds up through the gears.  Never ran hot either even on 90+ degree days.
3.  I think your timing may be off, I always run mine between 8-10 degrees advance at idle in gear.
4.  Perhaps on ling climbs one should gear the tranny down to the second drive position?
Good luck,  the 56 is the best caddy to have.