Would any of you Vortec guys give me a recommendation on plugs?  I've done a little research and I know (if I go with Delco's) that I need the "LTS" series for Long Tapered Seat, but curious about heat range.  I've seen recommendations for everything from R42LTS to R45LTS on other sites, would like to get some recommendations from you folks.  I'm also considering Autolites - my engine builder suggested 26's but I'm not sure they'd be appropriate for Vortecs.  

What is the compression ratio of the engine going to be?
Iron or Aluminum Vortec heads?

Ok, since I didn't get a reply. I looked at your profile and see what you have listed for some engine specs.

(I snagged this info from another forum.)

After you have your carb and timing all set up correctly. Drive the car for a couple weeks. Then pull a plug out and see if it is light tan or dark brown. If its a light tan go one step colder. If it's tan, your good. If its dark brown go a step hotter.

Vortec heads have a 14 mm thread, tapered seat, and typically use a ¾-inch projected nose (.750) reach, small (5/8") spark plug socket. Some suggestions:

AC/Delco
R42LTS - Stock and a good place to start.
R43LTS (colder)
R44LTS (coldest)

NGK
TR5 (stock equivalent )
TR55 (colder)
TR6 (coldest)

Autolite
103 (stock equivalent)
AR103 (Racing)
AR104 (Racing)

AP605 (Platinum)
APP605 (Double Platinum – kinda pricey)
XP605 (Xtreme Perf)

Bosch (0.69" reach)
HR9DC
HR8DPX
4305
4458
4205

Here’s a good (really complete) xref:
http://www.angelfire.com/extreme4/sk..._REFERENCE.htm


|UPDATED|10/21/2011 9:02:20 PM (AZT)|/UPDATED|

Thanks for the great info.  I'm leaning towards the Delco 42's or 43's.  (Haven't bought yet).  You got my CR from my profile, but just so you know these are stock iron Vortecs (converted to screw in studs).   So what do you run in yours?  Gap?  Thanks again!

Wow Sarge, I like your loads of information. A plug that I went with for my E-tec aluminum heads is Denso IK16 (5303)...iridium............pricey..............gap is preset. 

I've had Bosch Platinum 4205's in mine since 12/30/03. If I remember right I think I set the gap @.045. I could really go a step hotter for the next set I put in.

Years ago I tried out the AC Delco Rapid fire plugs when they first came out. I was surprised at how well the engine I put them in ran. So I may go back to the Rapid fires (#8's) I'm about due for a new set of plugs.
 

@corvette440hp, Iridium's are nice. A definite must for any high hp engine. I run Iridium's in our "Blown" 586 rwhp LS1 '04 GTO. At 7000 rpm's I have yet to blow out the spark. And this is with stock coil packs and NAPA Belden plug wires.



|UPDATED|10/24/2011 3:00:49 PM (AZT)|/UPDATED|

Wow, that sounds (586 rwhp) like I can only dream of.................WOW!

Dave,
 I just noticed what your engine builder recommended.  Autolite 26's only have a .460 reach.
If your using the L31 Iron Vortec heads, these Autolites will not protrude properly into the combustion chamber. They will be shrouded by about a 1/4". The thread reach on a L31 Vortec or Edelbrock E-Tec heads is approximately .750 or 3/4".
 
You may want to mention this to your builder. Have him screw a 26 into the head before he bolts it on to the engine and take a look. You'll see what I mean.

@corvette440hp,
 I forgot to mention the torque at the wheels was 492 ft.lbs. Pretty good for only 346 cu.in.
Yes I have the dyno sheets to prove it too. Not bad for building up my first LS engine, eh? 

Good point, Sarge.  Yep, I've noticed in my recent research that the Autolite 26 would definitely not be a good choice.  He must have given me his standard recommendation for a non-Vortec SBC without thinking about it - he had not done many Vortec buildups (more of an old school type).  I'll mention it to him next time I talk to him.  Thanks again for the good info.  

Sarge, 492 ft. lbs. out of 346..............you can do magic............very, very nice! That is well done...........

Dave, Sarge is right on the money about the 3/4" reach, also 14mm, 5/8"hex for vortex heads. Edelbrock recommends Champion RC12YC plugs for their e-tec heads. I substituted the Dens plug Ik16 Iridium in place of the Champion plug.