I went to Bosch 4s two years ago when I switched out heads and cam.

I pulled a few plugs last weekend and they seemed to have held up well.

I think the preferred plug for Gen 3s are the GKN. I buoght some recently but decided not to install them since the Bosh plugs were OK.

Why are the GKNs preferred; they look very low tech compared with the Bosh?

What about different heat ranges for plugs? I'm running close to 11 to 1 compression with LS6 heads shaved 55 thou. Should I be running a hotter or colder plug than the standard heat range plug for this car?

I suppose heat range selection and plug choice is less critical these days since our engines have a VERY hot spark at 100K volts; right?

Thanks.

GKN makes driveline parts.

NGK makes spark plugs.

I am sure someone else has more useful information.


Andrew

I didn't like the bosch 4's for the simple fact that you can't gap them. So i run ngk tr55's gapped to .050"

Nate

How about Champion RC12YC gapped to .045

GKN makes the finest driveline parts available. They also fund my toys every two weeks.

Bosch 4's suck I gave my car missfire's on the dyno. Switched to NGK tr55's and no more missfires. BTW the +4's were new

really? I heard Bosch blows too but my experience has been OK. The NGKs look like the low tech Champion plugs from the 1970s.... you know, the kind that burn up quickly in high compression engines that have a low voltage spark.

I think with are high voltage spark that are engines put out, it doesn't matter too much.

In the bosch, the electrode is platinum which is a very high conductor of electricity. Most of the plug's tip is covered by insulating material. This is why you can't (should not) GAAP them. In my car, these pups performed well with no corrosion or other visible wear.

I thought this construction was a good idea; no?

There was platinum on the plugs when you first put them in, but after your first few WOT rips it was all gone. Just a marketing gimmick. NGK TR55 Irridiums would be a good long lasting plug. Most people just run the cheap NGK TR55 Copper plug. You may want to consider going to a little colder plug with your compression, perhaps a TR6. That may not be necessary @ 11:1 though, I'm not sure. FWIW Bosch +2 lasted about 6K in my car and it was missing pretty badly.