79 Seville change fuel injection to carburator

[d j deluco]

I am wondering if anyone knows how I can change my 79 fuel injection to carburation. What are the pros and cons, and what parts are needed? Thank you for any help anyone can offer.

[Dave Shepherd]

Dist, carb and intake from a 307/350 olds to start, with elimination of both fuel pumps, installation of a mechanical stock pump or a low pressure electric pump. Fuel lines to the carb of course. That is the just the basics.

[planetcadillac]

Usually easier to fix the original system since it wasn't all that bad once you understand it.

As far as changing to carb, as was said, you can simply buy an Olds small block intake from say Edlebrock with 4bbl carb and carb distributor and that is the quickest way and then plumb for fuel. Or buy an inake/carb from a used 350/403.

What is the problem?

[waterzap]

What is wrong with the car? The EFI is great if it is all fixed.

I would rather change my Eldorado to EFI than my Seville to carb.

Having both, the Seville starts 1000% easier than the Eldorado. First time, every time. The EFI cars also has a bit more power. I understand the fuel injection better than the carbs, so for me, its no contest. This 70's fuel injection was a very good system. The main difference between the Seville EFI and modern EFI is that the Seville does not have a Mass Air Flow sensor. Car uses the speed sensors on the distributor. Reason apparently was that MAF sensor EFI takes more memory.

[planetcadillac]

EFI in the late 70s Cadillacs was analog not digital as it became in 1980-81. Technology was probably not available to sufficiently deal with the data being generated by a true MAF. Also using a MAP sensor (which a lot of car used until OBDII) was a pretty good tradeoff. The MAP sensor on the Sevilles is located in the computer box.

The speed sensor on the distributor was used for timing of the injector rail pulses. You might be able to still use the original distributor with a little rewire.

The EFI in the Cadillacs was very basic like early computers little in the way of logical input and no feedback. It was when digital came out in the 80 Eldo/Seville and 81 for others that we got more or less what we know now.

Most of the issues you face are related to fuel delivery and the coolant sensor. Most everything else is robust. I had a 76 Seville for years and never had issues with the distributor system. The biggest issues that I had were fuel pump problems and the climate control.

I also have a 1981 Chrysler Imperial FS with EFI. Its original and has what was the first true fully EFI system in an American car at the time. It had a MAF in the snorkel tube, and all of the other usual sensors and switches found on today's EFI. It does not have a check light but had a diagnostic computer available for it. It could be very cranky when it acts up but I have learned its ways and so far so good. Like has been said, EFI makes startup and takeoff a breeze.

Plus havin a car original adds value if you should ever sell it.

[bcroe]

The speed sensor on the distributor was used for timing of the injector rail pulses. You might be able to still use the original distributor with a little rewire.

The 78-79 Seville & 79 Eldo EFI used an HEI distributor with an additional feature.  The
special module was wired to an Electronic Spark Selector module on the firewall.  The ESS
gave extra advance (cruise) or retard (crank), and the regular advance was modified.   
Without the EFI, I recommend replacing this HEI with a conventional 76-79 350 carb type. 

Bruce Roe