late 69 427/400 spark plugs

[dick foehringer]

the owners manual says R43N which now is a R43XLS. but i have the 290 heads that use the tapered style peanut plug with no washer. what is the correct number? the car had the wrong plugs in it when i bought it. i guess they sealed up as it was running.
thanks, dick

[Clem Z.]

Re: late 69 427/400 spark plugs

R 43T is the correct plug but i would run R 45TS.

[dick foehringer]

Re: late 69 427/400 spark plugs

ok, i picked up a set of R44TS and they dont fit. i have the later 69 heads number 260? or 290??(i left the book in the car) that says they use the peanut style plugs. The 44TS body between the threads and the nut/seat is too large to fit in the hole. the previous owner had the regular style plugs in it and you can see where they only caught about half the threads and the seal washer rested on the beveled seat plane. guess they worked but sure not the right ones. anyone know what i should use?
regards dick

[Joe L.]

Re: late 69 427/400 spark plugs

Dick----

There are only 2 style spark plugs ever used on 1955-82 Chevrolet small block and big block engines-----14 mm gasketed seat and 14 mm tapered seat. If you have the '290' heads, they should be the tapered seat type. This means that "T" or "TS" suffix spark plugs should fit.

I don't rule out the possibility that some late 1969 '290' heads were machined for the earlier style, gasketed spark plugs. However, if that's the case, then the gasketed "N", "XL" or "XLS" suffix plugs should work. If neither style plugs fit your heads then you've got a problem that's beyond my comprehension.

[Clem Z.]

Re: late 69 427/400 spark plugs

post a close up picture if you can and as joe posted and i e mailed there are only 2 types of plugs for chevy heads,13/16" hex,gasket type and the 5/8" hex,tapered seat type

[dick foehringer]

Re: late 69 427/400 spark plugs

joe, i dont get it either. it had the gasketed style in it but you can see where the top half of the threads never touched anything. they had anti-sieze on them and you could see where it stopped. they didnt screw all the way in because the washer/seat bottomed out on the tapered seat of the 290 head. so i picked up a box of the TS peanut plugs an as i said they wont fit into the hole to even start threading. if they had been machined out larger then both would fit. these are the matching heads with dates that were on my 427/400. the engine had never been apart.
i dont get it??
regards dick

[Clem Z.]

Re: late 69 427/400 spark plugs

orignal gasket BBC plugs,"N" series,only had threads half way up because the threads were only in the bottom half of the plug hole in the heads. other 3/4" reach plugs have threads all the way to the gasket and they should screw all the way into the head. the orignal "N" plugs will not work in any 3/4" reach plug heads that have threads all the way to the top.