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Username Post: Kinda losing my mind with spark plugs        (Topic#346384)
Forum Newbie
Posts: 19
Reg: 07-11-17
08-03-17 12:49 PM - Post#2702672    

What I pulled out of the truck were ACDELCO R45TS. 14mm thread.
Guys at advance auto game me the wrong ones altogether. Some 18mm things (for the 323 maybe?)
I'm getting conflicting information on the PROPER spark plugs for this engine.
I picked up ACDELCO R45S, which won't thread.
Summit seems to think they will, but they don't.
Dunno why not, they are a 14mm thread.
I guess the question is, wtf spark plugs do I put in this thing?


Forum Newbie
Posts: 19
Reg: 07-11-17
08-03-17 01:07 PM - Post#2702673    
    In response to Flying_Dodo

OK, figured out why the R45S do not work. This engine requires the T, or tapered 5/8 socket for the plug threads to even reach to head.
Sorry, like I said, new to these engines.
Why does no site I've looked at so far list this?
Do I even have a 327? I haven't looked at the engine numbers. Kinda dirty down there.

Honored Member
Posts: 27764
Loc: San Francisco, CA
Reg: 11-26-02
08-03-17 01:44 PM - Post#2702678    
    In response to Flying_Dodo

The "T" in the spark plug no. means tapered seat. These are the plugs with the 5/8" hex that do not use a washer or gasket. The taper on the plug seals directly against a matching taper in the head.

I don't know what year the tapered seat heads were first used, so can't help you determine whether or not the heads are original to the truck. To identify what engine you have, please post the stamped number you will find on the block deck just in front of the RH head.


Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.

Chevytalk Moderator & "14th Year" Silver Supporting Member
Posts: 5083
Loc: Muskegon, MI, USA
Reg: 03-28-02
08-03-17 04:45 PM - Post#2702707    
    In response to Flying_Dodo

Since the heads on these engines are interchangable, you may want to pull a valve cover and see what the casting number of the head is.


65 Impala SS, 400sbc, Muncie M-22
66 Impala SS, 396, TH 400
69 El Camino, 350, TH 350
71 Short bed stepside 4x4, 350/TH 350
71 Snow plow, 4x4, 350, TH 350
72 GMC Shortbed, stepside, 427/TH 400

Forum Newbie
Posts: 19
Reg: 07-11-17
08-03-17 05:24 PM - Post#2702710    
    In response to JimKshortstep4x4

I think I've found a solution. A freshly rebuilt 350 for 800 bucks.
Then I can spend time rebuilding this damned (supposed) 327.


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