1970 GTO 400 Spark plugs
 

Does anyone know why the spark plugs on my 1970 GTO 400 engine have AC Delco plugs #R45TS with a gap of 0.040 and the Haynes Manual says R45S with a gap of 0.035? It also has an HEI distributor, and a 4bbl Holley carb, if that makes any difference. The R45TS has 5/8 socket size. Appreciate any help. JCIWOLF:

HEIs usually use a little wider gap.Tom

What casting number cyl heads are on the engine?

Tapered seat plugs weren't used on '70 model heads.

Appreciate the reply, I didn't know that. jciwolf

I will check that out tomorrow and get back to you

If no one minds me asking, if you have an HEI distributor, what gap should you do the plugs? What is a little wider gap?? Thank you, Carmine.

.040-.045..no need to go anymore with the older style plugs.

to "ol Pinion head I'm sorry I took so long to reply, the only numbers I found on the heads were: right side,(passenger), 1043 and gm3. Left side,(driver), 1063 and gm3. So far I have no idea what this means, but I know the number 7 spark plug is a royal pain to replace thanks to the steering shaft going right in front of it. I suspect this is routine for most goats. I will keep looking for an answer, hope you know. Thanks jciwolf

Hey wolf,

Look in the middle above the exhaust outlets of the head as shown below.

http://i325.photobucket.com/albums/k...pslnddxjmw.jpg

I will look tomorrow as today is over for me. I didn't see anything other than what I posted but I can look again. Thanks for the pic. jciwolf

Can't find any numbers on either head, only numbers are 1043 and 1063 right and left plus the gm3 on both. If there are more than that it would have to be further up on the heads and no offense I don't want to pull the covers. Any other ideas would be welcome. jciwolf

My only other thought is that if the heads had been "worked" as in ported or any other machine shop work to the heafs it may be a common practice to grind off the factory head numbers to indicate that they are no longer stock factory heads. I too have unmarked heads on my 455 and they have had port work and valve work done to them. Just a theory really.

jciwolf, those are the date codes on the heads, so cast January 4 and 6, 1973 which will point to 4x castings with 2.11/1.66 valves, possibly with screw-in rocker studs, and have 98 cc chambers. These were the standard head on the 400 4-bbl engines for 1973. On the left cast boss next to the valve cover there should be a stamp of 3, 3H, 4, or 4H (most likely 3/3H for the 73 castings).

Dennis

Thank You Dennis for this information. I just got paper work from a previous owner who had work done on this car. Apparently he had the motor bored and the cam enlarged. He said he wanted to restore the car, but new child and lack of body skills and wiring and of course the big enemy, money. I will be reading the paper work and motor service report this weekend. Stand by for my results!! Thank You again for the information and your time researching this for me. I am thoroughly Impressed with your knowledge and help, and the forum. So glad I joined in. jciwolf:)

Sorry it's taking me so long to post a reply but the unthinkable happened tonight, I was entering a rather long reply and the site logged me out on timeout! Apparently it didn't notice I was still typing and logged me out due to no entry! I will try again tomorrow. jciwolf

at the end of the day the seat for appropriate spark plugs changed on heds for either 1972 or 1973 (I'd have to look into it);
A 1970 400 (with lets say) #13 heads should use R45S plugs
If my memory serves me correct, the "t" (tapered seat) heads used the same heat range, but just went to the T plugs;
I believe that R45TS should be correct.

Going off memory:
R = Resistor(?)
45 = heat range (numerically lower indicates a cooler plug)
T = Tapered seat
S = this is either 'radio Suppresion' - or something to do with the tip.

I know the OE plugs for my car (#12 heads) are R44S which is one heat range cooler - this is a plug that is long since NLA;
In the past I have run either R43S (which I think are now also discontinued), or R45S - which I believe are a smidge too hot for my compression...
I have sourced some R44's and 44S plugs;
I am sure I could find someone to suggest that if I see Delco plugs in the 44 heat range, I see nearly become unhinged.
;)

Well if I don't get logged out I'll state what I have found out about this 1970 GTO. The previous owner head the original motor bored and stroke because the 455 head wanted to put in was damaged beyond repair. Instead of buying a new motor he had this motor bored and stroked, to 4.15 x 4.21. New crank , don't know what brand or #'. A Lunati cam, also don't have #'s either. All and all at the time of everything being done, he had himself a brand new motor with tons of items from Jegs, Flowmaster, and Stainless Steel Brakes Corp. Due to a lack of total motor knowledge, there is a multitude of unanswered questions I have. First there are no wiring diagrams of added parts and deleted parts, also some of these I have no idea what they are. For example, I have a sensor on the right side of the intake manifold,( passenger side), that is three wire and no idea how it is supposed to be wired in. Guessing 1 wire is power,(black with red tracer), 1 green possibly ground, and 1 dark blue think this may be signal but where does it go? So many more things, I have opened the harness and found cut wires and a lot of splices that are not factory and were done pretty bad. I think this is long winded enough, but I want to thank everyone who has replied to this wonderful journey!! jciwolf:huh:

They would be dated I043 and I063 which would be Sept 4th and 6th, 1973, making them '74 heads. Now they could be 46 (350) or 4X (400 or 455) heads, found on the center port. And the R45TS would point to the 400/455 head (350 used the R46TS plugs).

According to the notes I have gotten, previous owner wrote down 4X heads. You are right on the money!! Hope you can read my 4/7/17 post, lots more things on this goat. Most I am not sure of. Thank You again for your help and time. jciwolf

The sensor on the right, passenger side, is a three wire unit /w green, black red tracer, and dark blue. Don't know where the dark blue goes, possibly signal wire??
I tried to get a hold of offenhauser but no luck, not even by phone. I believe it it a 360 degree model, asked Summit but they don't know either... they only sell them!!! Any help appreciated. Thanking everyone for their support and advice jciwolf