Question: 1986 Spark Plug Question - AC Delco Rapidfire

[chris123]

On my 86 Convertible with the aluminum heads, I purchased the AC Delco Rapidfire Spark Plugs, the #1's which are GM part #: 19250960; I've checked with a few sources and they all seem to agree they are the correct ones. The AC Delco plugs that came out were part #: 41-629, and have the small metal washer on them for proper seating; the Rapidfires do not have the metal washer; just wanted to make sure these were the correct plugs.........

Regards, Chris.

 

[G Winter]

You need the washer. I think they also need to have about 3/4 in of thread.Would have to double check that. I know that is the case in my 90.
You should be able to feel if the seat is flat of tapered in the head.

 

[chris123]

You need the washer. I think they also need to have about 3/4 in of thread.Would have to double check that. I know that is the case in my 90.
You should be able to feel if the seat is flat of tapered in the head.

Thanks; I think I need the #5's instead of the #1's; the #1's that I have don't have the washer; I need to verify that the #5's have the washer before I order them......

 

[Hib Halverson]

DO NOT install Rapid Fire 1's in your heads.

In 86 all convertibles and late-production coupes got aluminum heads. Early production coupes got iron heads.

Generally, spark plug listings show only the iron head plug, which was a half-inch reach, taper seat plug. The aluminium heads take a 3/4-in reach flat seat plug

OE was the FR3LS
ACDelco aftermarket: 41-629
ACD aftermarket platinum: RF5 or the 41-800

If you want the best plugs on the market regardless of price, I'd use the Denso IK16.

 

[chris123]

DO NOT install Rapid Fire 1's in your heads.

In 86 all convertibles and late-production coupes got aluminum heads. Early production coupes got iron heads.

Generally, spark plug listings show only the iron head plug, which was a half-inch reach, taper seat plug. The aluminium heads take a 3/4-in reach flat seat plug

OE was the FR3LS
ACDelco aftermarket: 41-629
ACD aftermarket platinum: RF5 or the 41-800

If you want the best plugs on the market regardless of price, I'd use the Denso IK16.

Hib: I know you've been around from quite awhile, so I trust your info; I've had so many people comment that the #1's are correct, then the #5's are correct, etc. etc; not sure which info is accurate; I may just stick with the 41-629's to be safe, unless you can confirm that the #5's are correct for my '86 convertible with the aluminum heads?

Regards and thanks, Chris

 

[Hib Halverson]

Hib: I know you've been around from quite awhile,

Some say, "Far too long".

so I trust your info;

Oh, man. Have I got you fooled?!

I've had so many people comment that the #1's are correct, then the #5's are correct, etc. etc; not sure which info is accurate; I may just stick with the 41-629's to be safe, unless you can confirm that the #5's are correct for my '86 convertible with the aluminum heads?

Regards and thanks, Chris

The RF1 is a 1/2-in. reach, taper-seat, projected tip, plug for cast iron Gen 1 SBV8 heads.
The RF5 is a 3/4-in. reach, flat seat, projected tip plug for Gen 1 SBV8 (L98/LB9) aluminum heads and the 90-95 LT5 head.

Your heads require a 3/4-in. reach, flat seat, projected tip plug.

The RF5 is a high-performance plug for your application. The 41-629 is more of an OE replacement plug for your application.

I'll let you decide, based on how you drive, which of them to use.
Good luck with your plug changing.