News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

1973 Cadillac running rough after new plugs

Started by O. Ramirez, March 27, 2021, 12:25:43 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

O. Ramirez

I changed out my plugs put anti seize on the threads and that clear gel on the plug end now it

O. Ramirez


The Tassie Devil(le)

G'day Oscar,

I realise that your post has caught the current truncation problem, but check to see that you haven't crossed a plug lead when putting them back on.

Bruce. >:D

PS.   You did check the gaps before you installed the new ones?

PPS.   If you put the old plugs back in, is the rough-running still there?
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

O. Ramirez

I will put the old one back on tomorrow do you have the plug diagram from the distributor?

O. Ramirez

And Bruce they said at the auto parts store that they were gapped already I will install the olds ones tomorrow

The Tassie Devil(le)

#5
The firing order is 1-5-6-3-4-2-7-8 and the rotation is clockwise.

As for which is No. 1, that will depend on who last installed the Distributor.

They might have already been gapped, but someone could have dropped one, or more.   No matter what someone says, I always check.

Bruce. >:D

'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

O. Ramirez

Is there a way to check if the wires are bad? Bruce

TJ Hopland

Also note on this engine #1, the odd bank is on the right/passenger side of the car which is different than most other American engines from this era.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

O. Ramirez

Tj do you think the jell I put in the wire plugs might affected the spark?  Checked the wires they all look in order. I will buy a cap jig tomorrow do you know at what gap they need to be?

The Tassie Devil(le)

The Gap for 1973 should be .035".

Any set of Feeler Gauges will do.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Cadman-iac

The gel should not have any effect on the spark, it's purpose is to prevent the spark from jumping down the outside of the plug to ground, and to make removing the plug wires a little easier.
  I don't know where you got your plugs, but the guy who told you that they were already gapped is full of, well, you get the point.
  Plugs are put in the box with an approximate gap, but it can be changed/ closed in shipping and handling if they were dropped at any time. It doesn't take much to make the electrode bend.
Rule number one when installing plugs is always check the gap.


  Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

O. Ramirez

The plugs I bought for it are ac delco rapid fire and they are gaped at .040 should I bring the gap down to .035?

76eldo

Gap them at 35, make sure that all of the boot connections are snapped on the plugs, and re check the firing order.
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

TJ Hopland

Isn't there something about it being difficult to gap an exotic metal tipped plug without damaging the tip?

I would not think 35 vs 40 would make that big a difference but I don't know that for sure.

I just did a quick search about those and there does seem to be people running them on points systems so I guess they are a reasonable choice.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Daryl Chesterman

#14
Oscar, I worked at NAPA for 14 years, and we found out that it is better to stay with the type of sparkplug that the car was designed for, unless there has been an electronic ignition installed in it.  In your case that would be the AC Delco R45XLS (or whatever was originally recommended, if they are still available) and they would be gapped at .035.  The Rapid Fire plugs are indeed pregapped to .040, but as others have said, the gap needs to be checked before installing them for reasons previously stated.  The wider gaps (up to .060) have come about because of the higher voltages that electronic ignitions have, thus enabling the jumping of a larger gap and a correspondingly hotter spark.  With the Rapid Fire plug that you installed, the wider gap would require a higher voltage to jump the gap and maybe that is what is causing your engine to not run properly.

T J, it is possible to regap the newer style spark plugs, but one has to be very careful to not pry against the center electrode.  The platinum and iridium used for the center electrodes is extremely brittle and will break off.  This is a good article about the materials used in spark plugs.  Note the "Installation Best Practices" at the end of the article.

     https://www.knowyourparts.com/technical-resources/electrical/sparkplug-science-precious-metals/

       

It is also possible that one or more of the spark plug wires is defective.  This is a good video of how to check your spark plug wires.

     https://www.youtube.com/watch?v=4_EFGAFxi1w

If your old spark plugs make the engine run better, you might ask the parts store to take back the Rapid Fire plugs


Post was truncated:  edit to add on      ...especially if the counterman was the one who convinced you to get the Rapid Fire plugs instead of the OEM style.  Most parts stores will not take back plugs that have been installed, but if the counterman recommended them, that is on him and he needs to make it right

cadillacmike68

If you have points & condenser ignition, I do not recommend any type of platinum plug. Get the old style copper core ones and their gap should be .034 or .035.
Regards,
"Cadillac" Mike

64\/54Cadillacking

Ive tried numerous plugs on my 64 and so far there isnt much of a difference in the way the engine runs when using different plugs. But Autolites so far felt a bit smoother vs the other brands.

I will say that NGK makes great plugs, and Ive installed them in the 64 before without issues although its a colder plug, even in my Lincolns, NGKs seem to run well in everything. Just make sure the gap is correct for the engine or close to stock.

The problem with new AC Delco plugs and the majority of the domestic brand plugs, is that they are all made in Mexico or China now so you dont honestly know if they are still well made like the NOS ones. NGK and Denso plugs are still made in Japan and the quality differences is noticeable just by comparing the the plug material and looks side by side.
Currently Rides:
1964 Sedan Deville
1954 Cadillac Fleetwood 60 Special
1979 Lincoln Mark V Cartier Designer Series
2007 Lexus LS 460L (extended wheelbase edition)

Previous Rides:
1987 Brougham D' Elegance
1994 Fleetwood Bro
1972 Sedan Deville
1968 Coupe Deville
1961 Lincoln Continental
1993 Lincoln Town Car Signature Series
1978 Lincoln Continental ( R.I.P.) 1978-2024 😞