Bosh platinum on 3.4 DOHC

[NORBI]

We just did a tune up on a 3.4 DOHC (92 CS Int) and salesperson in Staus Auto recommended us a BOSH double platinum spark plugs and then my friend told me that they are one of the best plugs but not for 3.4 engine. WHy is that and can it cause any damage to heads or engine at all?

[ctx46]

if there not good for em... than Im fucked, I have been running them for a year now with no related problems.

[nerfbars]

No they wont cause any problems at all, they are perfectly safe. There suppose to be a pretty good plug. I run AC Delco Rapid Fires, but if I were to try anything else it would be the Bosch.

[GnatGoSplat]

Bosch plugs are terrible when used on an engine with a waste-spark ignition system, which is pretty much all W-body engines.

This is because 3 plugs fire with a reverse current, and the 3 plugs firing in reverse will lose material from the platinum center electrode.

This accelerated wear causes the center electrode to wear down, and the plugs cannot be regapped due to the fact that the electrode is flush with the ceramic insulator.

[NORBI]

SO i want to know how long till i will have to change them on 3.4. And can they cause any harm to the engine?

[GnatGoSplat]

I think I had Bosch platinum in my Cutty for 10k miles and the gap had increased 2x in 3 of them. So I'd say probably a year or so depending on how often you drive. It won't cause any harm, it will just be excessive spark gap in 3 plugs. Sometimes this can cause missing if the gap is big enough.

[NORBI]

Thanks a lot Shawn you guys really helped me a lot lately.

Thanks again.

[gpse3200]

If you want a really nice platinum plug, go to GM and buy their platinums. They come standard as a double platinum, and they would be perfectly matched. The olny thing is that you pay for that blue box, $6 a plug.