Bosch 4s

[Cailen]

Been meaning to post this since I pulled em but haven't gotten around to it until now.

Pulled this from my 95 Blazer 4.3L. This plug was the worst by far, though others looked similar. The truck had 200,000km on her at that time and the plugs had only 10,000km on them.

[OverBoardProject]

I'm probably the only person here that likes Bosch plugs, although I don't have them in my Blazer (I'm doing pretty good with splitfires and I'm only using those since there were 6 new ones in the glove box)

But when I was thinking about those Bosch 4 plugs I kinda figured that they have all the spark in the world. But in theory they block the fuel mixture from getting to the spark.

And this theory is partly proven from Dyno testing where they index the plugs (aim the plugs so the spark is facing the valves) Which does give the motor a little power gain.

[MT-2500]

I have been replacing plugs for 45 years.
I have learned the hard way.
GM use ACDelco plugs.
Ford use Mortercraft plugs.
Cry use mopar/champions plugs.
Sometime bosch and autolight and other plugs will run but Most of the time they will not run right because they do not get the right heat range or the plug is not made for the vechicle specs.
Or in other words use the the right OEM plugs the good book calls for.
And you will have a lot less headaces and grief.
MT

[rjrobb2]

I wish I had found this site before the last plug change. I put the Bosch P4s in and am already getting an idle that was not as smooth as with the AC Delco plugs and it was only a couple thousand miles ago.

I really don't look forward to doing this again.

Joe

[Cailen]

I really don't look forward to doing this again.

I know they aren't as easy as some other vehicles, but taking them off is made a LOT simpler by removing the wheels and working through the wheel well.