[unruhjonny]

I have some plugs here that my brother with a '77 (400) TA should be able to use;
I am not up to speed on what replaced what, or when, but my 1993 Delco catalogue lists the OE plug for a 77 TA as being R45TSX, but if I look around, I can find listings for R45TS8.

If I recall correctly there was a short period where Delco was pre gapping plugs - I believe that the "8" denoted the gap;
But
I also believe that the "X" also denoted a wide gap plug;

I have done my fair share of reading, and i have the nagging feeling that at one point the "TS8" was the "TSX" - but i know that when GM would discontinue a part number, they would sometimes phase it out, so that demand for the old part number would trickle down to match the depleting stock of the old part.

Question:
Are the R45TSX & R45TS8 interchangeable?

These are perfectly good NOS plugs, and want to have my info straight before I give them away.

Was the R45TS8 ever the OE plug for any 1975-1979 Pontiac 400's?
(again, I am asking because this 1993 catalogue lists R45TSX for all 1975-1979 Pontiac 350, 400, and 455 applications)

[Formulabruce]

I have a breakdown chart at home with the info. Will post later.
BUT. Nobody in their right mind, even in Canada , should be running a 45 heat plug with alcohol in the fuel.
44 is MAX heat..

[unruhjonny]

thanks, I will pass that on.

['ol Pinion head]

X stood for the Extended tip of the electrode.

AC R45TSX plugs were OEM in at least '77-79 Pontiac 400's & '80 Turbo 301's.
The only '75 & 76 400 T/A's I've tuned on, had worked early big valve heads amongst many other mods.

[Formulabruce]

Here's some info for you I promised Your 8 is listed with the 6
R=Resistor
4= 14 mm thread
5= Heat range
T= Tapered seat shell design
S= Extended tip
X= WIDE GAP ( H.E.I.) 6= .060" ( 1.5 mm gap), 8= .080 ( 2mm gap)
5, and 6 heat range plugs were used when there was NO Alcohol in the fuel.


PS. I was Removing these hot plugs from almost new cars at the dealership due to cooling issues and transmission failures.

[77 TRASHCAN]

Is the 45 plug too hot for a 7.6:1 400, now? even with ethanol now?
My 77 came with R45TSX plugs, .060 gap. I am sure the TS8 plugs were .080 gap.
I have never seen the TS8 plugs, in a vehicle, or as a listing for plugs, when I sold parts, from 1985-1998, when these engines/vehicles were commonly in use.

The last of the Olds V-8's had 2 different plugs they used, R45SX .060 gap and R45SZ .080 gap. When the book called for the "Z" plugs, I always tried to get the customer to buy the .060 plugs...

[Formulabruce]

X=.045 gap 6= .060, and 8= .080
The plain X is a given at .045 as standard HEI Gap.
>> IF.>> the 7.6:1 CR 400 is Not running over 190 degrees at the T stat, you could use these.
Ditch the EGR. Dont need .060 or .080 if the EGR is disabled.
You do Not want ( automatic) trans temps over 200
IF I was to run these I would use a AC Delco 170 T-stat.
Alcohol has higher ( but weaker) octane and engines work harder running on it. ( note crusing range differences on brand new cars window stickers for easy proof)
I was working at a Pontiac dealership when these poor cars were new and plugged and restricted.
A '77 180 hp 400 can easily get 220 hp with minor mods not even seen.

['ol Pinion head]

Experimented w running numerous sets of R44TSX's. Tinkering on '79 Oldsmobirds, I can't remember anything other than R46 somethings. On EGR valves, I used to jamb a .177 pellet up a new piece of hose. Numerous of our local "wizards" used to whack the EGR valves with a big ball peen hammer...real smart.

My only purchased new, & the latest built, Pontiac product was built in early Oct of '79
have never ran across a set of R45 TSB's, have quite a few sets of old stock AC plugs tucked away.

[Formulabruce]

Ya know, OPH, ya got me thinking about these "6" and "8" plugs.
I did see 46's as well, but I seem to recall the "6" and "8" plugs were from the parts room, and I "think" they were for cars burning oil ( worn rings) .

[padgett]

My cars get either Rapidfires or Iridium.

[nUcLeArEnVoY]

Sorry to necro this thread, but this is the first I've heard that the .045" plugs will run hotter on a low-comp engine than wider gaps.

This is very interesting, because lately my '79 has been running kinda hot at idle this summer, and I put in ACDelco R45TS plugs this past December. Before that, I had .060" R45TSX plugs in there for only about a month or so. I pulled a couple of my my plugs recently to look at them and the insulators are almost perfectly white like they're new, while only after a month, the .060" plugs that I replaced had more browned, discolored insulators (could've just had a rich tune, but you never know)... could that mean these .045"s really are running a lot hotter? FWIW, I blocked off and deleted my EGR at around the same time I put in the .045" plugs in December - it was pointless, anyway; I have true dual exhaust with no cats. I fill the car with REC-90 pure gas without ethanol, and the motor is just a 400 w/ stock 6X heads and a mild cam that pulls 17-18" vac at 750RPM idle.

Wasn't there a GM TSB recall for the .060" gap plugs in the 70's, though? Where they replaced them with .045" plugs since the 0.060"'s were prematurely ruining distributor components? That's the main reason I switched to the .045" plugs.

[77 Canamman]

I run nOS green stripe R45TS plugs gapped to .045" in my nearly stock '77 W72 400. Car runs fantastic, and no misfires at any speed. I strictly run 90 octane non ethanol fuel.