only DUAL platinum plugs are recommended ..
for the Allanté, the AC/Delco Plat plug i used is the 41-902 ...
this DUAL platinum plug will fit the 4100, 4500 and 4900 engines
on all Cadillacs.

you wont find it listed in the GM books for the Allanté 4100 engine ..
or for many other engines, but it is the proper plug ...

keep in mind, not all platinum plugs are equal .. read on

the choice of plugs was per a GM power train engineer recomendation of going with
AC Delco plugs for a 1995 to ?? 4900 engine .. . and after driving the car with
the new plugs, i gotta say that it was an excellent advice ..

what is the difference between the 41-936 / 41-902 ? heat range and expected application.
the engineer is a hot rod kind of guy, and has experience with the one he recommended ..
i just went with it.

the 41-902 size is IDENTICAL to the ones i pulled out, except for the top/bottom platinum
pads (ground & central elctrode) and the body is SS (i think) .. the internal ceramic insulator
was exactly the same size (determines heat range).

the difference in cost between the real McCoy .. ACDelco and the aftermarket platinums is small ..
easy choice for me. i guess if you really want to save money, the standard plugs w/o platinum are
about $25 per set. some of you might enjoy spending weekends changing plugs every two years .. not me.

on ACDelco's site,they list the following platinum plugs
1987, 1989, 1992 Allante(4.1/4.5) 41-936
1991, 1993 Seville (4.9) 41-902

as i stated at the beginning, the 41-902 dual platinum fit all three engines
the 4100, 4500, 4900

two more things ...

coat the threads with anti-seize
AND
the primary boots with DIELECTRIC
(both ends of each wire).


if you know the gent, please keep it to yourself
as he ahs requested



name withheld by request

Stealth...

you have a 4.1. Same is true for the 4.1 or 4.5. You can substitute the dual platinum plugs for the later model 4.9 conventional Cadillacs in your engine.

The dual platinum OEM plugs have a tiny pad of platinum welded to the tip of the center electrode and to the ground electrode. The platinum will never wear so it protects the plug from wear or the gowth of the gap so they will last forever.

Most all of the aftermarket platinum plugs have a platinum center electrode but nothing on the ground electrode.

By the OEM wires I mean the parts listed by GM as replacement parts. There shouldn't be a choice of wires...just the ones released for service as the OEM replacements.

Usually with the dielectric grease you can just squeeze a dab into the boot and twist the boot as you install it to spread it along the plug. Do the same with the distributor, yes.

Be careful to not over torque the plugs on installation. The tapered seat plugs require very little torque to seat and seal.

Installing platinum plugs in a 1988 Allanté

Before starting you will need:
1. a SMALL ratchet .. no Ifs, no Buts.. a MUST!
2. dielectric grease
3. antiseize compound
4. 8 plugs, pn 41-902 AC Delco. The case is 8#41-902 ACDelco.
5. Primary wire puller
5. fuel filter
6. distributor rotor (if you need plugs, this one is most likely also ready to go)
7. Inspect Distributor cap -
8. Inspect primary wires -
9. Fender protection

suggest blow/ clean or whatever is needed to remove debris from around plugs. I sprayed with engine cleaner and rinsed

1st, place a heavy blanket on the fender for protection.

blind-inspect (using your fingers) the primary wires to determine if you will need a new one here and there (about $7 each)
due to damage. Also inspect distributor cap.

disconnect all the primary wires you can from topside at the plugs. Make sure you pull the boots not the wires.
A puller is available for about $4.

dabb connector ends of each plug with dielectric grease (AFTER installation) for moisture protection and apply a tiny
bit of antiseize paste (BEFORE installation) on threads of each plug

raise the car on the lift, and from underneath, remove the three REAR primary wires and plugs closest to the passenger
side. that took about 10 minutes. ratchet and socket. installed three new ones. cannot reach the 4th plug from this angle.
since car was up there, changed the fuel filter, by the rear drivers side wheel .. 5 min.

dropped the car, removed the air-intake and duct all the way to the throttle body. Now you can remove the 4th plug
from the top .. ratchet / socket and a 2 in extension. It is right by the side of ABS ac***ulator .. about 20 min, this
one plug requires a bit of patience and you will basically have to climb and lay on the engine compartment to do it ..
use that blanket to protect the fender .. installed new plug, 4th.

installed air-intake and ducts and a new air-cleaner. made sure the primary wires are in their holder or the manifold
will burn them.

Apply dielectric grease to inside of each end of each primary wire (including distributor end) and then plug in
all the wires to the spark plugs from topside.

removed/replaced front 4 plugs, 5 min. Repeat the primary wire process.

The old plugs i removed were R44-LTS6 ACDelco, iron tips.

hints? .. remember to do a blind inspect of the primary wires with your fingers and feel for damage or roughness ..
one of mine was burned through by the exhaust manifold .. this is common on caddies.
all this stuff i had read about changing plugs had me thinking all kinds of horrors, and posponing the job.
none of that happened - there was no need to remove anything else or undue the moutns.

again, as you may know, i have a 4100 .. Dont know if the same applies to a 4500.

i got frustrated of looking for the right plugs at the local part houses, so I went to the Caddy dealer,
ordered a set of dual platinum plugs for a 1996 Seville, 4.9L.
Got pn 41-902 AC Delco. Cost $60 for the set. Someone told me the Champions (about $10 less)
are just as good .. I choose to play it safe on this one and went ACDelco. $10 is not enough to gamble.
After all, these are 100,000+ mile plugs. They way we use these cars, these plugs may well go
200,000+ miles. So the cost is small if one looks at it this way.

the fuel filter was $24. afterwards, checked the old one, it was fairly well plugged. just a matter of maybe a few more
tanks of fuel would had given problems.

so .. what is the trick? Only to remove the rear plug closest to the drivers side from the top. you must use a really
SMALL ratchet .. it pays to buy one if you don't have a small one.
oh, one last thing .. on checking the distributor cap and rotor .. pull it off and see if the rotor shows signs of
blackening in the backside center area, a sign of severe aging .. replaced it as this center is known to crack/burn
through after aging starts blackening it and you will get a shut down on the engine. cost $5

that is it ...

oh no.. wait .. did i mention you have to raise the hood lid?

afterwards, test test the car .. give it a 2 second burnout .. it makes one FEEEELL GOOOD ...

one other thing .. FWD Cadillac cars

engine right bank is closest to the firewall and it is numbered 2-4-6-8 from the passenger side to the driver's side.

The cylinder nearest the passenger side headlight is number one. The one nearest the driver's side headlight is
number 7.

The FRONT OF THE ENGINE is on the passenger side.
The REAR OF THE ENGINE is on the driver's side.

The ENGINE'S LEFT BANK is to the front of the car.
The RIGHT BANK is toward the rear of the car.

The left bank has the odd cylinders, 1-3-5-7 arranged from the ENGINE'S FRONT TO ITS REAR.
The right bank has the even cylinders, 2-4-6-8 arranged from the ENGINE'S FRONT TO ITS REAR

that should cover anything you ran across .. i hope.


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