Author Topic: Correct spark plugs  (Read 1033 times)

2ndbaser

  • Newbie
  • *
  • Posts: 2
    • View Profile
Correct spark plugs
« on: February 16, 2018, 12:48:21 AM »
I'm replacing some old spark plugs and I'm not sure which ones to buy. 350sb with '69 3927186 heads. A couple years ago I had a mechanic do some work and he put in Autolite 26 plugs. They show a reach of .46. The auto part store recommended AC Delco R45TS which has a .433 reach.

Everything I read on the internet says the reach for that head is 3/8.

Can someone recommend a plug? Should I pay extra for platinum plugs?

Thanks.

Everett#2390

  • Member
  • ***
  • Posts: 118
  • ^Bess
    • View Profile
Re: Correct spark plugs
« Reply #1 on: February 21, 2018, 02:38:19 AM »
AC 44, No, save your money.
A flashlight is a case for dead batteries.

JKZ27

  • Hero Member
  • *****
  • Posts: 528
    • View Profile
Re: Correct spark plugs
« Reply #2 on: February 21, 2018, 11:30:23 AM »
R45TS are tapered seat plugs, don't use them unless you're using 70's heads with tapered plug seats. Your 69 "186" heads should use washer sealed plugs with 13/16" hex. As Everett said, AC R44, R45. Some Z28 guys are using Autolites with good results. Don't use platinum plugs.
John
69 RS/SS Cortez Silver, L48 MC1
68 RS Ash/Ivy Gold 327EFI M20

Kelley W King

  • Hero Member
  • *****
  • Posts: 966
    • View Profile
Re: Correct spark plugs
« Reply #3 on: February 21, 2018, 12:59:44 PM »
I think I have tried most all (special) plugs. Split fire, platinum, ect. I really think what fires them is much more important.
69 Z28 RS Scuncio Hi Performance
69 SS L78
67 SS Chevelle
64 Corvette
66 GTO Tiger Gold
77 Trans Am Special Edition

Stingr69

  • Hero Member
  • *****
  • Posts: 654
    • View Profile
Re: Correct spark plugs
« Reply #4 on: February 21, 2018, 02:26:19 PM »
Autolite 85 will work well.

68Zproject

  • Hero Member
  • *****
  • Posts: 1863
    • View Profile
Re: Correct spark plugs
« Reply #5 on: March 20, 2018, 02:32:28 PM »
 J12-YC Champion is what Jerry said to use years ago.  I don't know if things have changed but that's what I use.
68Z28

X33RS

  • Hero Member
  • *****
  • Posts: 1034
    • View Profile
Re: Correct spark plugs
« Reply #6 on: March 20, 2018, 03:49:14 PM »
As mentioned the 186 heads are gasket 13/16 plugs, not the taper 5/8 plug (R45TS)

I prefer the extended tip plugs that have the "S" on the end of the part number.  Example R45S   All this does is put the electrode slightly deeper into the combustion chamber for a more complete burn and better combustion process.   If you run an R45 for example, same plug, but you'll clearly see the ground strap and electrode are somewhat hidden up inside the plug.   We used to call these plugs oil burnin plugs because back in the day we used them on engines that were burning oil, less likely to foul the plugs since the electrode was hidden up inside a bit LOL.

These days I use Autolite.   For the 186 heads you'll want Autolite 85's or 86's.   The interesting thing about these is that they are already extended tip plugs and as far as I know that's the only way they come from Autolite, they don't make the non-extended tip (oil plugs  ;D)

The only difference between this and their racing plug is a shorter ground strap that exposes a bit of the electrode.   I cut the ground strap back a pinch on the standard Autolite plugs for the same affect.