69 427/390hp Spark Plugs

[Salvatore I.]

I have seen prior posts on the preferred AC/Delco spark plugs for a mid-year BB. I think in the discussion, the car was a 66 BB. The AC R45XLS plug was suggested as a replacement for the R43N or R44N standard plug and I assume that this could also apply to a 69 BB (427/390 with 4 BRL carb)?

I wanted to get a hotter plug and so I would use the R45XLS as suggested. (The car currently has a set of R43N's in it!)

My question is: What is the standard length of the R43 or R44N plug? Are these about 3/4 inch in length from the seat? In other words, for the 69, will the R45XLS plugs be too long and protrude down the cylinder too far hitting the top of the piston? Or is the seat length (thread depth) the same on both plugs?

If these are too long, does anyone know what is the suggested replacement plug? Napa suggested a R44XLS....but they are the same thread length as the R45XLS plugs....

Thanks!

[Clem Z.]

Re: 69 427/390hp Spark Plugs

the change to taper seat short thread plugs was in 1970 so if you have "N" series plugs you have the 3/4" reach and that is what the R45XLS is.i have used extended tip plugs in BBC engine with 12.5:1 CR pistons which have a much higher dome than the one used in BBC street engines so interference is not a problem

[Dave S.]

Re: 69 427/390hp Spark Plugs

Sal,
Why not use a standard plug for a Big Block like 44N, 45N, R44N, R45N, if you want a hotter plug. They are more common than the 43N's and much more affordable. 43N's are too cold and too expensive if you buy the old style AC Delco plugs.

[Alex K.]

Re: 69 427/390hp Spark Plugs

Clem,

I have a 67 427/435hp with TRW-L2308A pistons and 074 open chamberd heads. Do you think the AC45XLS would be ok in this setup?

Thanks in advance AL

[Clem Z.]

Re: 69 427/390hp Spark Plugs

i never ran that combo but have used 074 heads on 454s with 12.5:1 pistons BUT i always indexed the ground electrode to between 9:00 and 3:00 o'clock position

[Alex K.]

Re: 69 427/390hp Spark Plugs

Thanks Clem,

I think I will do the same, AL

[Clem Z.]

any relation to iggy katona??? *NM*

[mike cobine]

Re: 69 427/390hp Spark Plugs

I ran the 074 open chamber aluminum heads on a stock bore 427 with TRW 12.5:1 pistons and used R43XLS with no interference. I was also pumping those slugs up and down a bit faster than you probably do, running 7200 rpm with them. I can't remember the piston number offhand, and even though L2308 sounds familiar, since so many TRW pistons have similar numbers, they could have been anything.

[Alex K.]

Re: any relation to iggy katona???

not sure,but my family thinks so because of my passion for racing/restoring corvettes

[Clem Z.]

that tells me you have heard of him *NM*

[Alex K.]

Re: 69 427/390hp Spark Plugs

Thanks Mike,

Yes they are the 12.5 trw pistons.and your right I could never pump out more than 6500rpm,you must of had a wild set up with a strong bottom end to do 7000+rpm with big block,sounds like one hellofgoodtime!!!!!

[Alex K.]

Re: that tells me you have heard of him

Yes.Back in the 59 to 62 era,in Cleve,Ohio,when Iwas trying to make my 57 Cevy go faster on the drag strip,my father would come out in the garage and say 'Who do you think you are iggy Katona'. I believe he was darn good driver/race car builder in the 40's,50's early60's.

Thanks AL