Correct Spark Plugs?

Reply Subscribe

Thread Tools

Search this Thread

Aug 10, 2004 | 12:16 AM

griffths

Thread Starter

Racer

Joined: Dec 2002

Posts: 421

Likes: 2

From: Long Grove, IL

Correct Spark Plugs?

I am in the middle of installing a new stereo and went to the auto parts store to buy some new spark plugs (Just a little bit of scope creep at work

) and there was not a specific listing for a 1969 427 400HP. So, do I need R43XLS or R44XLS plugs? I drive a mix of city and highway so whatever the General put in there is what I am looking for.

I have looked in all the places I can think of but came up short for an answer; CF Archives, FSM, emission sticker, Web and corvette FAQ. I cannot believe this is the "I can tell you, but then I have to kill you" type of information....

Thanks

Jay

Aug 10, 2004 | 10:05 AM

comp

Team Owner

Joined: Sep 2003

Posts: 88,393

Likes: 2

From: eville in

ttt

Aug 10, 2004 | 11:13 AM

clem zahrobsky

Le Mans Master

Joined: Mar 1999

Posts: 6,744

Likes: 1

From: delmont pa

Cruise-In I Veteran

Cruise-In II Veteran

Quote:

Originally Posted by griffths

I am in the middle of installing a new stereo and went to the auto parts store to buy some new spark plugs (Just a little bit of scope creep at work

for every day driving i would use AC R45XLS plugs as the fuel wash will cool the extended tip plugs

Aug 10, 2004 | 11:56 AM

PRNDL

Team Owner

Joined: Jul 1999

Posts: 26,545

Likes: 46

From: Huntersville NC

Quote:

Originally Posted by griffths

I have looked in all the places I can think of but came up short for an answer; .............Thanks

Jay

Did you look in your owner's manual?

For 1968, for 427 V-8 my manual says original equipment, AC-43N and Heavy Duty (Colder) AC-C42N. For smallblock they give you four choices! So it depends on your useage. I don't think you can get those exact numbers anymore. I have used 43,44,45 and never noticed any difference.... can't even remember what's in there now.

Aug 10, 2004 | 12:19 PM

Rolm

Instructor

Joined: Jun 2004

Posts: 198

Likes: 0

From: Long Island NY

I learned a very expensive lesson on my son's Mazda Mx6 I decided to upgrade his NGK plugs with the latest and greatest technology with the Bosch plugs. The engine ran great for abought 300 miles and then the engine started missing after chasing my tail for a few weeks and $300 later I decided to go back to the stock NGK's and that fixed the problem. So what does this said "stick with the same plugs the engine left the factory with" Trying to out-smart the professional engineers may just cause you the same crap as I went through. From this point on I will stick with the factory-specked plugs on all my engines even my lawn mower

Aug 11, 2004 | 02:34 AM

marky mark

Burning Brakes

Joined: Aug 2000

Posts: 1,211

Likes: 6

I am running R44 XLS and am going to try R45XLS tomorrow as my carb is running a bit rich and want to see how it works.

These plugs were originally listed for aluminum headed engines back then but they work fine in many applications. I did notice that Champions has a very slight increase in length so I'm sticking with what I know works in my 427/390. I'll let you know how the engine ran with the hotter plugs.

Regards, Mark

(

their plug)

Aug 11, 2004 | 11:49 PM

griffths

Thread Starter

Racer

Joined: Dec 2002

Posts: 421

Likes: 2

From: Long Grove, IL

Thanks to all who responded.

PRND21 - The owners manual is the one place I didn't think to look, however after looking in my owners manual I cannot find a listing for spark plugs.

Jay

Aug 12, 2004 | 02:23 AM

Ironcross

Race Director

Joined: Nov 2002

Posts: 12,142

Likes: 54

From: Taylor Michigan

The lower number in AC plugs are basically for performance however not necessarily good for the street as they will fuel fowl. 42`s & 43`s in any configuration should be avoided. 45`s will be the best choice even in higher performance engines {11-1 and solid cam} that are street driven.