EFI for 1959 Coupe De Ville

[MWachtel]

Hi All - Long time Cadillac owner (20 years) but new to the forum.  I own a mostly restored 1959 Cadillac Coupe De Ville.  I recently (2020) had the engine rebuilt as although original and operating was quite the smoker.  The rebuild solved the smoking but on my drive cross country last summer I was the repeated victim of vapor lock.  I am not sure if it was the winter fuel from covid, the altitude (drove route 66 but stalled out equally at sea level as well as 7000 feet), the heat wave (July), or just very unlucky.  I have decided to convert to an EFI system as due to the experience I no longer trust the car in temperatures above 80F.  Has anyone done this? Which system do you recommend? and most importantly will this ensure (largely ensure) i don't have this problem anymore?

[Caddy Wizard]

I did this on a 49 and am doing it on a 55.  Absolutely will eliminate vapor lock forever.  Only downside is that the engine will want to idle higher than the transmission likes (the way the fluid coupling is designed), so shifting into and out of drive and reverse will be clunkier.  But other than that, it will be fantastic.  Good fuel economy, improved power, better acceleration, smoother.  Less smelly exhaust.  More stable coolant temp (eliminates lean-out overheating).  Tricky thing (not terribly difficult) is creating a bracket on the throttle body that attaches the TV rod at exactly the same radius from throttle shaft and angle relative to throttle butterflies.  Biggest pain in the neck is electric pump and new tank.  The sump system recently introduced by Edelbrock might be a nice choice.

Lots of good providers:  Edelbrock, Sniper, FiTech, etc.

[MWachtel]

Thanks! Great to know.  Better fuel economy than my 11mpg on the highway (12 going downhill) will always be welcome.  The vapor lock wasn't an issue with the lead additive but after the engine rebuild and even running on pure gas didn't seem to make any difference. 90F was guaranteed vapor lock.  I'll be OK with the clunking.  Thanks for the note on the bracket.  And i haven't heard about Edelbrock so will definitely check that out.  Cheers!

[bcroe]

When AC started to come in, they added a fuel return line.  Might be
done with an extra tube on the fuel pump, extra inlet (besides vent)
on the gas tank.  The idea was to keep enough fuel circulating back
to the tank, that it did not sit and get hot in the engine compartment. 
I converted some of my cars to this as I added a bigger engine and
radiator.  Along with other cooling upgrades (just coming up to 70s
standards) did it for me.  No vapor lock in Death Valley and some
other notable hot situations. 

You will need all the above for EFI anyway, might try the return
circulation and other upgrades (fan, clutch, baffles, overflow catch
tank with matching pressure cap) first and see what it does for you. 
Bruce Roe

[Clewisiii]

Fuel filter with vapor return fitting.

[G Pennington]

Just curious... did you install an electric fuel pump on your '59?  Under the car back by the gas tank?  In series with or in lieu of the original mechanical pump? 
The '49 thru '62 331/365/390 series engines are notorious for vapor lock due to the location of the fuel pump.

[76eldo]

I'd try an electric pump to supplement the mechanical one or eliminate the mechanical one.
EFI seems a bit drastic to eliminate vapor lock.
These cars were driven in the heat when they were new and certainly weren't unreliable.
My dad bought a brand new 64 SDV and we drove from Phila to California and back in the summer of 64 with the AC on the whole time and the car never skipped a beat.
How is your radiator ? Was the block flushed out completely when Yih did the rebuild? If it runs how now it will run hot with EFI too.

Just an opinion.

[TJ Hopland]

I have an FiTech.  If I was to do it again I would consider the Holley Sniper which wasn't quite out yet when I did mine.

[MWachtel]

Thanks all! Great suggestions.  To answer a few of these:  1) Electric Fuel Pump:  Yes i did install one (in series in addition to the mechanical pump, in the back near the tank) but it made no difference ... well perhaps a little difference but not enough that it really mattered.   I insulated the fuel lines and protected the pump from the engine but it still vapor locked.   2) Radiator:  No i did not flush the radiator.  Honestly i had driven the car with the original engine on premium with lead additive for 18 years and i only had the issue with vapor lock once ... and it wasn't even a hot day.  Subsequently, after the engine rebuild, it was ALWAYS a hot day when it vapor locked.  Cool days it was unaffected.  And by hot i mean mid 90s to 100s ...  and in traffic was almost always certain death. But yes, need to check that out as well  3) I have been looking at the Holley Sniper with return line. While agree a more extreme solution, I love taking my car on the road and want to continue to drive long trips.  I feel conversion to EFI will eliminate my worries every time the mercury climbs towards 90.

[fishnjim]

Might be where you live, not in the sense of climate but the gasoline they supply there.   
If non-attainment, it's RFG and we know from good data the ethanol causes an azeotrope with some of the gasoline components, so it boils lower in the mid range.  I have the graph, but too much info 4 here.   I also have the typical period gas analysis, much difference in heavies.
Someplaces, like near the lakes, etc. sell non-ethanol for boats, which I think is the old MBTE formula, as they're supposed to run oxygenate and the EPA hasn't shut it down, so it might be worth a test run.   I don't think the lead additive was as much helping as what it was mixed with, and if not broke don't fix it.   Some use av gas, but at a hefty cost penalty.   Modern cars are not pushing the compression like these jewels.   aka: high compression blues!
I'd experiment with different gas from different stations.   It also changes with the seasons.   So if you haven't driven much and have winter gas in summer it'll affect it.   They control the vapor pressure for smog reduction.
I'm converting the '58 to electric pump only because of unreliable supply of FPs.  4 in a row is too many.   I'm basically done, but have one more issue to resolve before I fire it.
FI requires a return loop.   Electric does not, if you use the proper pressure controlled pump.

[TJ Hopland]

Getting the fuel pump in the tank and having a return line seems to get the highest satisfaction ratings on the conversions.   OE's have been doing return-less systems for a while now but it doesn't seem like we are quite there yet for the conversions.   Once you get the pump outside the tank you start having priming loss of prime issues along with noise and heat issues which all seem to lead to early failures.

I don't have a in tank pump, I'm running what is generally called a surge tank and I can still have vapor lock on the hottest days but it is fairly easy to clear if/when it does happen.   I have also noticed recently I can hear my pump more than I used to so I wonder of its maybe getting a little stressed being hotter than if it was back in the tank.     

[MaR]

You can get returnless kits for most aftermarket EFI systems. You can also get heatsink fins for external fuel pumps if you feel like yours is overheating.

[TJ Hopland]

I know you can get returnless kits but when I was still active on the EFI forums a couple years ago people often seemed to have issues with them that went away when they went to a return.     I don't get why people don't seem to want to do a return.   You got to run wires and often times new fuel lines front to back anyway so why not run one more line while you are down there?  If you do get any air in the system for any reason its easily burped out with a return.   Not so much with returnless.  Its not like getting air in a diesel but they still run better without air. 

Another thing that seems to make them work well is if you can get a tank that was built for EFI.   They make quite a few for quite a few of the popular classic cars.    Take some time to do some research and see if any of those may be easily modified to fit your car.   I would take one of those over a retrofit in tank kit if it was reasonable to fit.   Even if you have to do some custom brackets or a filler I think you will get a better end result than modifying a non efi tank.  Tanks Inc is a good place to look at whats available and I think they finally added dimensions for those of us looking for something close. 

[bcroe]

I have no doubt the mfrs decided it was cheaper to electronically
limit the power to the electric pump, thereby regulating the fuel
pressure, than to buy a return line and pressure regulator.  It
may considerably reduce pump wear too, but I am not sure I like
the idea.  Bruce Roe

[V63]

One cause often over looked for vapor lock is "too lean" of a fuel mixture! A vacuum leak often the cause.

too far retarded timing, in an attempt to eliminate ping raises engine temp. Increasing probability of vapor lock especially with alcohol blended fuels.

If your vehicle has a clutch cooling fan ...I am not a fan of those at all. I prefer flex fans. 

Remember if you run an auxiliary electric pump (with mechanical pump)  everything is fine UNTIL the diaphragm in the mechanical pump starts leaking into the crank case! It can go unnoticed until disaster.

[Hillbillycat]

Hey, I have one of these cheap electric in-line pumps near the tank that I use to prime my lines when the car sat for a longer period of time to reduce stress on the starter and battery.

What do I have to do to prevent the diaphragm of my mechanical pump from failure you mentioned?
Not use the electric pump at all? Or just use for one seconds? I usually run it untill I hear a change in priming noise, which indicates fuel reached the pump up front. This is around 3 seconds.

[V63]

The way you are using it should not be as problematic.

But if the car starts stalling after the electric is turned "off"
then you might have a compromised mechanical pump and  likely leaking fuel.

[bcroe]

I have a 77 not used enough to keep the carb from frequently drying
out.  It pains me to think I will need to overhaul the starter about
3 times as often from pumping enough gas into the carb to start (it
otherwise would start on the first turn).  So the idea of an auxiliary
electric pump is very attractive.

HOWEVER, such a pump would only be activated while I am HOLDING
a pushbutton switch.  I cannot believe how many use a dangerous
toggle switch instead.  EFI cars use the ECU to turn it off.  Bruce Roe

[Hillbillycat]

I don´t start the car on the electric pump.
I just use it to prime the line and then turn off them pump. Then push the pedal to set the choke and start the car. Usually fires up within one or two revolutions.

Push-button is a good idea.

[The Tassie Devil(le)]

I only have the priming problem when the car has been sitting in my garage for extended periods, so I drilled a hole in the top of the aircleaner, directly above the primaries, and pushed a plug in there.

When I want to prime, I grab my priming container, and remove the push-in plug, squirt an amount of petrol in the hole, replace the plug, and it fires up immediately.

Once the car is out and about, and still being used a day or two after, it still starts first kick, so no need for a separate priming pump in the fuel line.

Bruce.

PS.   I apologise for the rough top on the air cleaner, but it is one of my other cars.