[GTP091]

I remember there were some threads on here a long time ago about platinum spark plugs being bad for the 3.4 'x' engine. I bought and installed Bosch platinum +4 for my car awhile back; then found posts on here saying bad idea go with oem ACdelco only. Any thoughts on this, or guys with good / bad results??

[3100 MPFI]

any BOSCH plugs are going to be bad, but the +2 and +4 are the worst.

First of all, the spark is going to go the path of least resistance, meaning the spark will always go to the terminal that is closest to the center electrode.

Also, the GM waste-spark DIS system has a hotter spark than just about any other system, and it will burn the platinum right out of the plugs.

Generally, when you put the +4's in the car, you MIGHT get 1000 miles out of them, and you will start to get symptoms of a misfire.

I stick with the AC DELCO rapidfires in 3.1 MPFI, 3100 SFI, and 3.4 DOHC cars.

[asylummotorsports]

Well to begin with you wasted your money on that MSD stuff!

The ignition systems an our cars are one of the things GM did exceptionally well, and really can't be improved on.

And MSD doesn't have a great reputation for longevity with MPFI or SFI.

And a big NO to platinum. Rapid fires are just fine, irridiums for the newer 3500's and such.

FWIW

[GTP091]

Originally Posted by asylummotorsports

Well to begin with you wasted your money on that MSD stuff!

The ignition systems an our cars are one of the things GM did exceptionally well, and really can't be improved on.

And MSD doesn't have a great reputation for longevity with MPFI or SFI.

And a big NO to platinum. Rapid fires are just fine, irridiums for the newer 3500's and such.

FWIW

I'm not worried about the money the MSD ignition parts cost I have lots of it. I just wanted to be able to fine tune the ignition and that's something the GM ignition can't do. They wouldn't have made the coil packs if they didn't do something.

[GTP091]

Originally Posted by 3100 MPFI

any BOSCH plugs are going to be bad, but the +2 and +4 are the worst.

First of all, the spark is going to go the path of least resistance, meaning the spark will always go to the terminal that is closest to the center electrode.

Also, the GM waste-spark DIS system has a hotter spark than just about any other system, and it will burn the platinum right out of the plugs.

Generally, when you put the +4's in the car, you MIGHT get 1000 miles out of them, and you will start to get symptoms of a misfire.

I stick with the AC DELCO rapidfires in 3.1 MPFI, 3100 SFI, and 3.4 DOHC cars.

Have you ever had platinums in a 3.4 DOHC or just the delcos?? I know of a few guys on here that put them in their LQ1's and had only good things to say. My car has had a miss since my crank sensor went out and I blew a bunch of money on other things trying to fix the no start problem it caused. I had put in the platinums long before this and they were great. But maybe they have worn out like you said and that's why it misses now. I can't remember what was in my car when I got it in 2001. Do the rapid fires say that on the packaging?? I went in to a store and saw regular delcos and platinum delcos but no rapid fires.

[3100 MPFI]

yes, I have used the bosch plugs in a twin cam. When I built the engine in my 1995 I had to drive it with bosch 4's until I could get to the parts store. It was REALLY bad.

AC DELCO rapidfire plugs for a 1991 TWIN CAM, the part number is 12

Rapidfire number 12 is what you need.

Don't listen to what the people at the parts store tell you. When I worked for Pepboys, they would tell us to push the Bosch +4's and when I refused, they started threatening to write me up, and fire me. Also, don't trust the parts store when they tell you the plugs are PRE GAPPED.

[SappySE107]

Originally Posted by GTP091

I'm not worried about the money the MSD ignition parts cost I have lots of it. I just wanted to be able to fine tune the ignition and that's something the GM ignition can't do. They wouldn't have made the coil packs if they didn't do something.

Want to buy an IAT chip, a throttle body heat shield, and a fuel magnetizer? They made them so they must do something. You can't fine tune without computer tuning. Retarding is all the MSD box can do. The coil packs will do nothing that the stock coils weren't doing.

[geldartb]

Originally Posted by SappySE107

Want to buy an IAT chip, a throttle body heat shield, and a fuel magnetizer?

aww man the cats out the bag now there goes the spoiler on my next mods.



but yeah unless your coil packs go to shit then theres no need to buy aftermarket. the GM ignition on these cars is actually one of the things GM did right.

as for spark plugs i went with plain ol AC DELCO plugs with my car 2 bucks a plug, and they work just fine.

even my 2.2 4cyl beretta didnt like the bosch plugs, dont even think they lasted 6 months and very little miles. yeah i made that mistake when i was young.

[Superdave]

I had nothing but problems with my MSD coils, they burnt up my ICM after a few hundred miles.


Rapidfires are platinum, i'd stay away from them as well. Either run the cheap Delco plugs or run the Iridium plugs. iridiums are well worth the money and they last for a LONG time.

[SappySE107]

When did rapid fire become platinum?