Spark Plugs for LT4
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Spark Plugs for LT4 (No Go)
How come you run the #12's? Doesn't the cross reference book call for #14's with the LT1/4 motors? I'm running #14's, and Datamaster doesn't show any spark retard from knock so I don't think they're heat range is too hot. But I don't race the car or autoX so maybe under those conditions one step colder (12's) might be better.
<edit> Those are excellent power numbers for those mods. Looks like you are right around 400hp at the crank. Man, I want an LT4...
[Modified by Lone Ranger, 9:23 PM 2/22/2004]
<edit> Those are excellent power numbers for those mods. Looks like you are right around 400hp at the crank. Man, I want an LT4...
I've run the #12 AC Rapidfires for the last 3 years.
Work great, much better than the OEM platinums that loose the pucks!
:)
Work great, much better than the OEM platinums that loose the pucks!
:)
[Modified by Lone Ranger, 9:23 PM 2/22/2004]
Advanced
Joined: Feb 2004
Posts: 57
Likes: 0
From: Birmingham AL
Re: Spark Plugs for LT4 (CaliforniaVette)
In their 2000 catalog (page 6), TPIS lists their dyno test for LT-1's and LT-4's as gaining 6.4 HP by switching to Bosch +4 plugs over stock.
I run the +4's myself, and I'm happy with them.
Your mileage may vary, though!
[Modified by nodoubt, 5:01 PM 2/23/2004]
I run the +4's myself, and I'm happy with them.
Your mileage may vary, though!
[Modified by nodoubt, 5:01 PM 2/23/2004]
Le Mans Master
Joined: Aug 1999
Posts: 7,339
Likes: 137
From: WilkesBarre PA
Re: Spark Plugs for LT4 (JasonL)
NGK TR55s are what I use. They also make a long-life version, TR55IX or something. This is the drop in replacement for LT1/4.
That's what I use.
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Spark Plugs for LT4 (nodoubt)
Based on forum posts, seems Bosch +4's have been hit or miss for Vettes. Some guys report problems with them others report they work okay, about a 50/50 split of opinions.
The clown prince of trick plugs is supposed to be Denso iridium, but they are expensive like $7 - $8 per plug depending on where you buy them. Lot of claims of hp increase w/ the Denso iridiums :crazy:
The clown prince of trick plugs is supposed to be Denso iridium, but they are expensive like $7 - $8 per plug depending on where you buy them. Lot of claims of hp increase w/ the Denso iridiums :crazy:
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Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Spark Plugs for LT4 (CaliforniaVette)
so... which ones? :skep:
http://www.acdelco.com/html/catalog/index_auto.htm
But this member submitted product review on the forum suggests using #12's:
https://www.corvetteforum.com/review...=461&TopicID=2
[Modified by Lone Ranger, 7:29 AM 2/23/2004]
Burning Brakes
Joined: Apr 2001
Posts: 994
Likes: 0
From: Jamison PA
Re: Spark Plugs for LT4 (JasonL)
NGK TR55s are what I use. They also make a long-life version, TR55IX or something. This is the drop in replacement for LT1/4.
Advanced
Joined: Feb 2004
Posts: 57
Likes: 0
From: Birmingham AL
Re: Spark Plugs for LT4 (Lone Ranger)
The clown prince of trick plugs is supposed to be Denso iridium, but they are expensive like $7 - $8 per plug depending on where you buy them. Lot of claims of hp increase w/ the Denso iridiums :crazy:
That's good, but doesn't measure up to the Bosch +4's 6.4 HP gain (per TPIS).
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Spark Plugs for LT4 (nodoubt)
The Bosch +4's are still hit and miss in C4 vettes. Your sig encourage comments on your mods. IMHO the only mods that are doing you much good are the 1.6 RR's with the LT4 ESC module to prevent spark retard from the rr's extra noise. Instead of some of that stuff, I'd put money into head work, long tube headers, catback, and a cam which you have listed in your under consideration list. Then you will see some return on the 52mm throttle body too. I'd top it off with a cold air intake.
Or sell it and get an LT4 to mod. I've thought about modding my '95 but the notion of replacing it with an LT4 car seems to make more sense.
Or sell it and get an LT4 to mod. I've thought about modding my '95 but the notion of replacing it with an LT4 car seems to make more sense.
Melting Slicks
Joined: Jun 2000
Posts: 3,215
Likes: 6
From: Tampa Florida
Re: Spark Plugs for LT4 (Lone Ranger)
Just depends on your application although not sure if slightly colder/hotter plug really matters on the later model EFI'd cars.
I run mine pretty hard...#12's work, so use them.
The Bosch +4's don't even make sense to me...tried them in another car and it ran worse. Gimmick in my opinion.
I estimate closer to 410 engine rated horsepower (ie stock is 330 rating, now 410)
I run mine pretty hard...#12's work, so use them.
The Bosch +4's don't even make sense to me...tried them in another car and it ran worse. Gimmick in my opinion.
I estimate closer to 410 engine rated horsepower (ie stock is 330 rating, now 410)
Race Director
Joined: Feb 2004
Posts: 12,517
Likes: 19
Re: Spark Plugs for LT4 (GlockLT4)
What is wrong with the plain jane ac-delco plug? I run a set in my L-98 and change them once a year. I have never had a failure and they take the msd and nos well. I blew the tip out of a platinum plug and this turned me off to them. Complete set of 8 is 10 bucks with tax. I personally would rather change a cheaper plug often rather than leave them in a long time. This gives me an annual look into the engine and I feel better about this. Just my $.02 :flag
Burning Brakes
Joined: Apr 2002
Posts: 1,083
Likes: 0
From: Spanish Fork Utah
Re: Spark Plugs for LT4 (Pete K)
I've been running the AC Delco RapidFire 1's in mine. The heads are Dart Pro One aluminum. Haven't had trouble with them, but admittedly I don't know what plugs I should even be using! Are there some publications somewhere I can read or some general guidelines?
Thanks!
Shayne
Thanks!
Shayne
Pro
Joined: Feb 2003
Posts: 540
Likes: 1
From: Taunton MA
Re: Spark Plugs for LT4 (sspackman)
for some reason GM cars don't usually run that great with any other plugs besides ac delcos. i would stay as far away from the bosch platium 4 as possible in my opnion bosch= :U
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Spark Plugs for LT4 (comp94)
This is really nitpicking, and I'm not attacking NGK plugs because I know a lot of guys use them and get good results both street and track. But one thing I noticed is the AC plugs fit better in the head's plug hole threads, at least on my car. The NGK's would want to wobble and chatter just enough that while spinning them in with my fingers after getting them started they would momentarily bind up (but a gentle wiggle/twist combo would get them moving again). The AC 41-906 stockers and the AC Rapidfire's did not have this problem. Before anyone blurts out that I must have had the NGK's cross threaded I didn't, okay? They threaded in okay they just had more play between their thread studs and the thread channels of the head than the AC's, which caused them to momentarily bind up. Once they were about half way in the binding that would happen every so many turns diminished. Same brand of anti-seize was used on all plugs, so not the factor.
[Modified by Lone Ranger, 1:41 PM 2/24/2004]
for some reason GM cars don't usually run that great with any other plugs besides ac delcos. i would stay as far away from the bosch platium 4 as possible in my opnion bosch= :U
[Modified by Lone Ranger, 1:41 PM 2/24/2004]
