New Spark Plugs

[JasonA]

I'm gonna have to get one of those impact universals.

The only one I found, out of two stores, was in that three-pack I mentioned from Sears. Given more time, I may have been able to locate one individually, but I was excited/anxious to get the job done so I spent the 30 bucks at Sears just to get the universal joint. My local Home Depot had a pretty lame selection of air tools. I didn't have time to run by Lowes, so I don't know what they had. I didn't visit any of the local True Values, because I figured they wouldn't have had ANY air tool socket pieces, but I could be wrong.

[Ranger]

Thanks Jason. There is a chain in Ill & Wisc. called Farm & fleet (Fleet & Farm In Wisc) that has a pretty good selection of tools. If I can't find one there, I'm sure I can get on from one of the many tool catalogues that come in th mail.

[Regis]

I completed a short "how to" page for the spark plugs. My main reason for doing so was to highlight my experience with the two different types of universal joints, and how much easier the job was with an impact gun universal joint.

http://www.jnjhome.net/cadillac/plugs.htm

That's pretty involved Jason and looks like a one paragraph of directions stretched to meet the 5 page requirement just like back in grade school. We used to refer to it as "pulling out the shovel". All that is really needed the proper socket and drive, a 6" or longer extension, torque wrench, gapper, and most importantly the gumption to do it. You access the plugs from either the side of the car( for those that are taller) or by lying across the engine (using a large piece of cardboard makes it easier and more comfortable). Changing plugs is not an endurance event and should be included as preventative maintainence (100K miles or sooner). Changing spark plugs is one of the easiest things to do on an engine, the Northstar included. It is not a big deal and shouldn't be made into one.

What did you gap your new plugs to? I think it's safe to say that .060 or .050 will work perfectly fine. I think it's interesting that you post a suggestion that .060 is "better" that .050. Wonder why the following year they went back to .050 if .060 was "better"? Perhaps the 97 model year was somehow more "special" than all the other years?

[BodybyFisher]

I think it's safe to say that .060 or .050 will work perfectly fine. I think it's interesting that you post a suggestion that .060 is "better" that .050. Wonder why the following year they went back to .050 if .060 was "better"?

Not to beat a dead horse, BUT

The above is a good point, and it is what has been bothering me, why is 97 so different? Because of the supplier? .010 is a BIG difference. The supplier determining the GAP certainly sounds like the TAIL wagging the DOG... Personally I would have used .050, since 99.9% of the information we received stated it was the gap. Will .060 work, yep.... As the gap widens, it will be .065, if you loose a pad, it will be .070....

I have said why is 97 so different?

ACDelco quoted .050

Champion quoted .050

Autolite quoted .050

We have members with 95 through 96 stating .050

We have members from 98 to 99 stating .050

These statements would bother me that we turned up:

On weaker or stock ignitions, opening up the gap CAN increase the spark kernel size, thereby creating a more efficient burn. The problem lies in that any added gap creates more strain on the other ignition parts.

Coils may not have enough stored energy to fire, or in the least case, not enough energy to cross the gap, creating a miss-fire.

Plug wires will break down due to the added resistance as the spark tries to reach ground.

Rotor and Cap, as well as points (if you still have an interest in prehistoric ignitions), and the carbon bushing in the center of the distributor cap will show early failures.

As many of us know that race, it is also possible to slow down a car if the gap is too big. I will get into this later when I describe proper spark plug gaps

Something many do not know, is that with Higher Compression ratios and Superchargers as well as Nitrous, in many cases smaller spark plug gaps must be used as well as the use of a much hotter ignition system (see at link below). These higher cylinder pressures require more energy to jump the spark plug gap. (NS is a high compression engine).

I suppose .060 work ok especially if the coils have been spec'd for .070, but WHY is it .060 and all other years have .050, .010 MAY make no difference now, but as these plugs wear and if you loose a pad, you could misfire at some point.. The logic behind the .060 is not strong enough for me to feel comfortable about it. If .060 works how would .050 work? Curiosity would get the best of me and I would try .050 given that some of the gaps in the old plugs were .055...especially give the plugs propensity for losing its pads....

[JasonA]

Geez, I've turned into the enemy for taking photos of the recommended tools to change out the plugs!!

*I* didn't say anything about the spark plug gap. *I* didn't say that .060" was the "better" gap. *I* didn't imply that '97 is a better year than any other. All *I* did was post a comment verbatim from a source we know and trust and preach like gospel here in Northstar land, and the reply is that the answer is somehow wrong.

We trust the engineers to program a sophisticated oil life monitor to keep our engines running for practically ever. We trust them to design world class timing chain systems that are practically good for the life of the engine. We even trust them when they say, "don't worry, that case half leak won't evolve into anything worse than it currently is." But I guess we don't trust them when they say the ignition system is more than able to operate the engine within a given range of spark plug gaps.

I guess I'll go back to changing my oil every 3000 miles...

[BodybyFisher]

I love the guru, I really really do.

Everything that GM states about the 97 is .060.... the manual and the underhood label, even the dealers who also read the GM spec.

But EVERY other source states .050.

While I love the guru, do you think he would REFUTE something that is in TEXT by GM and potentially make them look bad? Doubtful he would say its wrong... Listen, the ENGINEER sets the gap, NOT the spark plug supplier! While .060 is adequate, so is 28 PSI in the tires as is 32, as is 35, but 32 and 35 produce different handling results... Me I would go with the flow and use .050... but that's me and that is after a lot of support and research and its not an off the cuff opinion to be difficult..

[JasonA]

Mike, that's cool man. I'm not arguing with ANYBODY. But it feels like I have to keep restating why I wrote that ".060 is better" or that .060 is correct for every year. I didn't write or imply anything like that...I simply passed on the answer that I got, and I trust, and the fact that .060" is working fine in my vehicle. If your car calls for .050", and you're running .050", that's COMPLETELY FINE, and I don't want anyone to think I'm saying that they're wrong. I was just passing on what I was told.

[BodybyFisher]

I know Jason, im not arguing either, its just illogical that 97 is different. Maybe you have lower compression? There has to be another reason besides the supplier setting the gap, which knowing the testing done on the NS is illogical.. See this statement.... if your 97 permitted a larger gap maybe the compression is lower in that year?

"The rule of thumb on plug gaps is to open them up in .002" increments at a time. When the car (race vehicle) begins to lose power or slow down then go back .001-.002" and this in most cases is the optimum gap."

[JasonA]

The 1997 Northstar has the same 10.3:1 compression ratio as the rest of the 93-99 cars.

I don't think we should be so quick to discard the "suppliers" answer. Perhaps an earlier plug supplier said, "We can guarantee the platinum pad will stay on there for 80,000 miles, but the gap shouldn't open up too much after that, so you can still claim a 100,000 mile tuneup." Then GM may have said, fine, let's gap them at .050", and they'll be in the .060" range after the 100,000 mark.

Then perhaps they got a different plug supplier in 1997 that could guarantee pad retention to 125,000 miles, so GM may have said, okay, we'll spec the gap for .060", because if the pads are retained for the full 100,000 miles, they gap wouldn't have opened during that period.

Then perhaps they got a different supplier again in 1998 or 1999 and was back to the first situation.

I don't know the details. I know that most years called for .050" and at least 1997 (perhaps '98 also; I haven't seen anything for '98) called for .060". Some of us were on a "mission" to find an answer as to why the various years were different. I found one answer; maybe there's another. Maybe my answer is not correct, I don't know. All I can tell you is what my answer is, and that I realize that I don't know the spark plug supplier situation in the mid 1990s for GM. Is it possible that the answer I got is incorrect? Sure. Is it possible that it's correct? Sure. I don't know that it is or isn't, but I don't have any reason to believe that it's not, so it's all I can go on for now, unless someone can find a different answer as to why ONE or TWO model years would be one way and others are another.

[JasonA]

"The rule of thumb on plug gaps is to open them up in .002" increments at a time. When the car (race vehicle) begins to lose power or slow down then go back .001-.002" and this in most cases is the optimum gap."

By the way, this statement seems to support my answer source's suggestion that .060" is the "better gap". Opening the gap allows for a larger spark, provided the ignition system can handle it. The Northstar's ignition system can clearly handle it...and well beyond the 100k mile nominal service life for the plugs. My plugs didn't start misfiring until I physically broke one with the impact wrench and my sloppy u-joint.

Is .050" too conservative a gap on these engines, knowing that the ignition system is good for much more than that? Is .060" too aggressive a gap, knowing that the plugs can lose their pads and approach .070" or higher to stress the coils? I guess we all have to use our own personal experiences (or our underhood stickers!) to answer that question.

[JasonA]

I'm going to let this be my last post in this thread, since it has elicted so much emotion for some reason.

Changing spark plugs is no big deal to someone who's done it before. Changing brakes is no big deal to someone who's done it before. Rebuilding engines is no big deal to someone who's done it before. But it can be a big deal if it's your first time. I've changed plugs before. I've done brakes before. I've removed and rebuilt engines before. The Northstar engine is my first aluminum engine, and as we know, they can be sensitive to the service procedure you use. Do it wrong and you can mess it up. We all know that all too well.

On a separate topic, photo journals of instructions for a certain procedure are prolific on the internet. You can find photo essays of brake jobs, of stereo installs...of practically anything. I have one of how I installed the CD changer in my Seville. And I get 3-4 emails a year from people who say they've seen the page and have question about the install. Could I just have said, "you pull the carpet up and plug it in"? Sure, but the extra information always helps, and people appreciate being able to visualize the situation. I know that's always helped me in the past, even doing a procedure with which I'm familiar.

Marrying the two thoughts above, I was anxious about doing the spark plugs on this car because I had never done them before. I knew they'd be hard to remove. I knew that stripping the threads in the aluminum head are not unheard of. This is my daily driver, so I wanted to get it right. I broke a plug using a cheap u-joint with my impact gun. I thought that was an important piece of information that someone like myself, who is doing the plugs on their car for the first time, might like to know, and be able to act accordingly proactively instead of reactively.

My intentions for doing the write up were clear from the beginning. I wanted to highlight my experience with that u-joint, and say how much easier the job was after I got the proper tools. I never wanted to act like the spark plug changing encyclopedia. If you'll notice at the bottom of the page, I give full credit to "the fine folks at CaddyInfo.com". You people have helped me a lot over the years, and this particular issue was no exception. Reference the spark plug gap, on my webpage, I indicate to gap the plugs per the specification for the model year of the vehicle. I made mention that the '97 called for .060", but never made any judgement on which gap was more appropriate. I suggested to use the gap that your model year calls for. It's been that way from the beginning, since I first uploaded the page.

The only case in which a judgement was made as to which gap was "better" was when I copied an email correspondance between myself and another person, and I indicated that the passage was a verbatim copy. No judgements were ever of my own personal opinion, and I don't believe I led anyone to such conclusions.

As I stated above, given the climate surrounding this topic, this will be my last mention of spark plugs or spark plug gaps on this forum. I don't know how this topic created so much emotion, but it did and that's water under the bridge. If my intentions for doing anything relating to this topic were misconstrued in the past, let this post clear those up.

Thank you sincerely,

[brcree]

1. OK....so I have a 94 Deville 4.9. How the heck to ya get to the rear plugs to remove them? My 94 now has 245,000 miles on here...and NO these aren't the orig. plugs?

[BodybyFisher]

Deleted, replied in error to wrong post

[KHE]

You used an impact gun with a universal joint banging away so strong that you damaged your universal and you are blaming the wires? Assuming that each wire has been snapped back onto each plug and you heard the snap you have most likely cracked a plug in the back head.

Use an 18 inch breaker bar proper extension, new spark plug socket and snap them loose. That is the only way you will get them out. Soak them for 6 hours with a good corrosion rust breaker but then vacuum it out so the solution and debris stays out of the cylinder.

The.bond needs to be snapped, use steady strong stable pressure. If you are slight in stature, find a monster to do the job. I am 6'5" 230, and you need the strength to snap the bond.

Good luck to you.

He is replying to a 9 year old thread. He's wondering how to access the rear plugs on a 4.9 engine.

[BodybyFisher]

Its possible I read it wrong...and thought I was replying to the.last thread. Swore that I was however, it was about a misfire after using a universal and impact gun to remove the rear four, maybe I was reading a quote that was not clear, thanks kevin

Ill delete my reply, leave my quote in your post so its followable

[MAC]

HI, BBF! Glad to see you're back! I started reading this thread and noticed it's from '06. Anyway, whatever one has to do to get help. People here at Caddyinfo are ready to help. Speaking of which, here is a thread about removing 4.9L spark plugs.

[BodybyFisher]

Hi MAC, hope you have been doing well, thanks!