3.3 short stroke, what plug heat range?

[fred cook]

I am about to start a rebuild on a 3.0 block using 100mm pistons and cylinders. The pistons are Mahle cast to give 10.1:1 compression ratio. Cams will be from a 964 and I have an Electromotive XDi ignition to provide spark. I will be using ported Carrera heads that have been twin plugged. I need some input as to what brand and heat range spark plugs to use. The heads are cut for 12mm plugs. It's probably appropriate that it is nearly Halloween since I am "lost as a haint" as to which plugs to use! Total advance will most likely be in the 22-24 degree range.

[KTL]

What induction, fuel injection or carbs?

I use NGK 7 or 8 on my carbed 3.2 short stroke, as does a buddy with a 3.3L SS

For Bosch comparison I have a bunch of spare/takeoff old spark plugs that came out of the engine before I bought it and they are coincidentally 7 heat range. But the Bosch and NGK range is opposite. Just so happens that The NGK 6 and the Bosch 7 are in the range where the same heat range for each plug coincide.

[fred cook]

Originally Posted by KTL

What induction, fuel injection or carbs?

Induction will be via a large port CIS system, maybe with an adjustable WUR, etc. If that doesn't suit me, the addition of ITBs or carbs will be an external change not requiring going back into the engine. What I am trying to achieve is tons of torque with good power up to 6500 rpms or so as this will be primarily a street engine.

[Steve@Rennsport]

Fred,

I'd use Bosch BPR7EIX (14mm) on top & XR4-CS (12mm) on the bottom.