1974 Cadillac Eldorado ignition

[Scot Minesinger]

Working on a 1974 Cadillac Eldorado with points and condenser.  Electronic ignition was optional in 1974, standard in 1975 for Cadillac.  Owner is interested in going to electronic ignition.  The conversion kits for 1973 and earlier work well, but should I go to a 1974 stock system?  Is it same as a 1975.  If so I should be able to buy one on Rock Auto.  Opinions?  I'm inclined to go 1974 stock EI.

["Cadillac Kid" Greg Surfas 15364]

ASSUMING the correct components are currently installed (springs, weights, advance stops, vacuum advance, etc.) adding something like a Pertronix would be best if you don't have the capability of using a distributor machine to verify the curves on any replacement distributor.  Any HEI you get as a rebuilt will be a "shot in the dark" as far as the timing curves are considered.
If you can verify the curves of a replacement then of course the HEI is far superior to any modified points distributor.
Greg Surfas

[Scot Minesinger]

Greg,

Thanks and making sure I got this right, a correct HEI such as a known good used from a 1974 Cadillac 500 engine would be best, Petronix is second best (assuming the ignition set up now is correct) and worst is just order a rebuilt 1974/75 Cadillac HEI from Rock Auto.  Is that right?

["Cadillac Kid" Greg Surfas 15364]

Scott,
No best or worst.  Just make sure WHATEVER  distributor you use has the correct mechanical and vacuum timing curves.
Greg Surfas

[TJ Hopland]

Has this car got dual AC/PS belts?   How about a smog pump?    If so you could have minor clearance issues with an HEI with the inner belt hitting the cap and the lower body hitting the smog cross pipe.  Smog pipe just needs some minor persuasion.  The belt issue is best solved by going to the single belt system used in the HEI years.  Also would be a chance to change pulleys and eliminate the smog system if that was something being considered at the same time.

Those are not show stoppers but just several bits to add to the list of things that may need to be addressed if you make the change.   Also note that the HEI uses different wires so if it needs wires anyway not a big deal but if its got good wires then that is an additional expense.   Just doing a pertronix sort of thing or adding something like a MSD6 box triggering off of points don't get into any of those issues. 

IF I was going to buy a HEI I think I would go to Davis Unified Ignition.  They have a good rep and actually test them so you will get what you are supposed to get unlike a typical rebuild where one size may sorta fit all or none.   

[Scot Minesinger]

This is a single groove a/c and p/s belt system with a smog pump from the factory.  I have not seen the car yet.  The engine was rebuilt, so presumably the timing chain was replaced.  If it has a smog pump, I probably will remove it with that MTS kit.  The owner objective is to get the car to be a reliable good performing reliable driver.  Currently the carb needs to be rebuilt and the gas tank tank needs to be dropped to replace the sender.

[hornetball]

I've looked at the MTS pump delete, but all of the MTS kits specify that they are for dual-pulley cars and my car (a 74) has the single pulley.  So I've left the AIR system in place.

To Greg's point about making sure ignition advance is correct, the Cadillac VVI data has ignition advance on page 230 in the "1974 MVMA Eldorado Specs" section.  Go here:

https://www.gmheritagecenter.com/docs/gm-heritage-archive/vehicle-information-kits/Cadillac/1974_Cadillac_VVI.pdf

It's interesting to download the VVI documents from several years to see how the camshafts and ignition advances changed.  Camshafts definitely changed over the years but when I looked at RockAuto for a "stock" replacement, they listed a single part number covering all years.  So, caveat emptor . . . .

By 1974, the ignition advance was being used to control emissions in addition to performance.  For example, they list 2 distributor part numbers either of which could be HEI equipped.  I'll bet one was CA emissions and the other was federal.

[TJ Hopland]

Ya you look at the manuals from say the 60's there is just one spec per year for distributor and timing.   Look at one from the mid to late 70's and there can be several pages with 3 or 4 options per model.

I have not done it myself but I have been told Davis will build a distributor to spec if you ask.  I assume you would have to send them the spec you want and that it may cost more but it may be worth it to know its done right. 

I don't remember which vendor but I have seen listings for both the single and dual groove AC smog delete pulley kits but maybe it was a limited run for the dual groove.     Note if for some reason there are no plans for AC its not a problem and you can easily run a shorter belt direct from crank to PS.   Also note that a bolt on single groove PS pulley is very rare, almost all of the singles were press on. 

["Cadillac Kid" Greg Surfas 15364]

Scott,
Since you say you are going to eliminate the AIR you have a litle more latitude in distributors.  Seconding TJ's suggestion for a Davis (DUI).  They are bulletproof and yes they will "tune" them as you request.
If I can offer a suggestion, the DUI on my '76 is set for a maximum of 22 degrees at 3500 RPM and I set 10 degrees initial.
Vacuum advance should start at about 6 inches and be full in (20 degrees) at about 16 inches.
Thern again since the AIR is coming off I would suggest sending the carb to someone like Jet Performance and telling them what you have (modified by removal of the AIR and distributor curve).  They will re-calibrate the carb and with the vacuum advance connected directly to manifold vacuum and initial set at 10 degrees you should have a sweet running stocker.
Greg Surfas

[Scot Minesinger]

Jett rebuilt the carbs on both my 1970 Cadillacs before I started doing them myself.  They definitely know what they are doing.  Both run smooth at idle and are powerful at the stop light, plus they sound nice. 

The compressor and ps belt is independent of the alternator/water pump/air pump belts.  I hope MTS did not forsake the 73 and 74 engines with air pump and single grove ps/ac belts, and that they offer an air pump delete belt set up.  I will figure out something, do not want the air pump, it makes everything difficult, less performance, source of a vacuum leak, and less room to work on engine.