Hey guys I am thinking of installing bosh plus 4 plugs on my 94 LT1 vette
give me some input, the plugs are free and new in the box, it came with
the car when i purchased it. :skep:

thanks
Capp and Stella :seeya :flag

 

You won't see a bit of performance gain from the plugs, but they will last a lot longer than any single electrode plug out there.

 

These plugs don't make any sense at all, why whould you basically block the fuel getting to the spark by 4 grounds. I mean, think about it, how are you getting a better spark from 4 grounds. My school tested these things out, and you could barely see the spark on it as compared to a regular spark plug. So, with such a small spark, you may not burn all the fuel in the cylinder. I have tried them in my vette, but I just decided to get the acdelco OEM plugs after a couple months because of what I found out in class.

 

Two questions....

1) what school

2) what is the difference in the air/fuel mixture's access to the spark in the Bosch Platinum +4 and the surface spark plugs used in NASCAR? Those are the plugs we use in our research engines here at UCF (Penske, Hendricks, and soon-to-be Evernham motors) Sparks will arc across the shortest distance between the two sharpest points in the system. By having 4 grounds on the plug, you have provided 4 times the material for the electrode to arc to, providing longer life for the plug.

 

I have them in mine,and they seem to work good.Not one hick-up since they've been in.

 

Same here... Had them in for about 25K miles now and no problems whatsoever...

I have them in my daily driver also...

 

I have them in mine, in my wifes dodge intrepid, and a ford truck I have. Cant say they run better, but they are just as smooth. TPIS claims a 6 hp increase with them. By the way, these arent just something that bosch came out with on their own. Back in the 80's I had a 82 RX7, and the factory NGK plug had 4 tips on it. The Champion replacement only had 2, and I can tell you it did not run as well as the NGK did. Over all I dont think any plug is going to make a big difference in how your vette runs.

 

I've heard a lot of trash about these plugs and others but the only thing I have to report is this: The +4 have been my 92 LT1 for almost 2 years now or about 45,000 miles. I average 24-27 MPH on the interstate at 80 MPH (as long as there is no stron winds or rain). There have been absolutly no issues to far that I am aware of aside from running a little rich.

 

Have them love em....won't go back to OEM :flag :chevy

 

If they are new adn FREE
Put em in.

I too have wondered about the theory behind all this special plugs??
Take for example plug indexing:
The idea is to get the opening gap of the plug to point towards the piston so you get the fuel/air mix INTO the plug gap so it will get more of the spark thus burn more efficiently and more power (so the theory goes).
Now if you go and block all access to the fuel/air mix by using 4 ground lugs it seems it would be harder to get the intensity of a single indexed plug??

(not based on any knowledge, just my own conclusions) :jester

I'm sure they work fine or they wouldn't be selling,
Again you have them and they cost nothing so you have nothing to loose.

 

Don't buy Bosch +4's, buy NGK TR-55ix iridium's. Better plug for same money, closer to OEM design but improved spark performance over OEM. The NGK ix iridiums are very close in design to the Denso (Accel) Iridium Power line of plugs, and there have been dyno proven gains of a few rwhp with the Denso iridium's. The Denso's are like $11/plug (!) but the NGK's are around $5/plug. The iridium plugs are popular with the forced-induction tuners because the spark is (apparently) more resistant to blow-out at very high cylinder pressures.

As for me, I'm running AC41-906 OEM's, only because I installed them before finding out about iridiums.

P.S. Be sure to use a good quality aluminum or copper based anti-seize compound on the plug threads!


[Modified by Lone Ranger, 4:27 PM 1/28/2003]

 

The only thing that plug indexing *might* do is help light of the flame more consistently, but experimental data shows that it doesn't matter. If there is enough turbulence in the combustion chamber, thus homogenizing the fuel/air mixture better and creating better (and more) mixture motion, and there is sufficient voltage at the plug to ionize the gas in the gap, the mixture will light off. It doesn't take much to start the actual mixture ignition process, and once the kernel is formed (the ball of fire at the plug, not to be confused with the spark, which ignites the kernel), the spark plug doesn't have anything to do with anything any more.

One other important note...a plug with 4 ground electrodes, or even two for that matter, does not spark to more than one electrode. Each time the plug fires, it arcs from the electrode to ONE ground and ONE ground only. Thus the intensity of the spark isn't controlled by the number of ground electrodes on the plug, but rather the current the ignition system can pass to the plug. The voltage that is discharged at the plug is a function of the gap (larger gaps require more voltage), the presence of sharp corners on the electrode and ground(s) for the energy to concentrate at (the spark arcs from one sharp point to another, not across rounded areas), and the ionization energy of the fuel/air mixture in the gap at the time of plug firing.

Oh, and one more thing...just because it sells doesn't mean it works. People have been buying Splitfires for years and they do absolutely NOTHING. Actually, the fact that their ground electrodes are created by splitting one ground electrode in half, thus creating two weaker electrodes which have been known to break off and get wedged around the piston at the top ring and do fun things to the cylinder wall....it's all been a bunch of really good marketing on their part.

 

Just my personal experience with these plugs is that they are crap. I installed a set in my old car and it immediately developed a bad stumble to it and just overall ran like crap. I checked and re-checked everything and it didn't help. Later that day I replaced the plugs with the old AC Delco's I had just taken out and my problem was solved.

Maybe I just got a bad batch but to me that's just unacceptable. I paid $32 for 4 spark plugs, if they can't have better quality control than that I don't want them. Changing plugs on that car was easy too, if you've still got stock manifolds on your vette I wouldn't dare put anything but the proven plugs back in it because you'll be some kind of mad if you have to replace them again any time soon.

I've had good luck with NGK's, Autolites and even good old AC Delco. I finally found the part number for non platinum AC Delco plugs for the LT1 if you're interested, costs like $11 for all 8.

 

I'm always interested in available plugs for the LT1, fire away with that part number, I want to keep it on file just for good measure... :yesnod:

 

I'm surprised that you had to pay $8/each for them....I just got a set for my vette for ~$35 for all 8. I don't discount your experience, as we've all had different ones, but all I can say is that I've run them for ~2 years in my '87, ran them in my turbocharged Mustang, and something else I can't remember and had no problems. But that's why we have the forum...more experiences to share.

 

I've run them in my 8000+ rpm 'lil Hondas, ran 'em in my '96 LT1 and even re-used them in my current LT4/Hotcam conversion. They work fine.

As far as people saying that the 4 grounds "shroud" the spark from the intake charge... take a look at the physical positioning of the plug. By opening up the area directly above the electrode you are actually unshrouding the spark compared a regular "over the top" ground. Plus the fact that with 4 grounds you should theoretically increase your chances of ionizing a gap (which I believe would be the main point).

But different engines end up with different tunes and all have their idiosynchracies. All I can say is that the Bosch +4's have worked well for me in several different applications.

 

I once found a cross reference chart that showed the AC Delco 41-904 was equal to the R44LTS non platinum plugs. The problem though is that later LT1's came with 41-906's so I don't know if the same cross reference still works. I would just look it up but I lost that chart when my computer crashed a few weeks ago. :smash:

This would have been at least 4 years ago, so it's very possible that prices have come way down since then.