The V8 Owners Forum -

I am running a Rover V8 3.5 with a compression ratio of 10:1, it has a full MSD ignition system (6T and billet dizzy) it also has a edelbrock 500cfm carb and an offenhauser 360 inlet, exhaust manifolds are fairly free flowing tube 4-2-1 system with a balance pipe about a 3rd of the way down the system.

Now at the moment it has a set of NGK plugs just off the shelf as if it were a standard 3.5

I would like to know what others are running in their engine plug wise and what is the best heat range to go for for and also for "go" and MoT able emmissions ?

All help gratefully received, the other way of getting this info takes ages of trial and error and i am hoping someone will have a good idea of where to start !!

Am considering these.....NGK BPR6EIX they are iridium apparently, anyone else using them ?

I have recently put these NGK Iridium plugs in my 3.5, which has 9.75 CR & a fast road cam.

Very happy with them, finally managed to eliminate a flat spot that I had been struggling to cure.

I left the gaps as they came out of the box, although I did check them all to make sure they were consistant. I think the gaps are factory set anyway, they warn against adjusting them as you can damage the iridium tipped centre electrode.

They are expensive plugs, I got a set from the States through ebay & even with shipping it was still cheaper than anywhere I could find over here. Maybe even better now with the £/$ rate as it stands

Thanks for that, i will go ahead and get them, i was told about them on another forum but wanted to check before i spend a mint on 8 plugs !!

Iridium plugs - as far as i'm aware are for durability - not a better spark. Tend to get used in modern cars where its difficult to get to the plugs to change them.

Ehhhhh MSD & Iridium plugs won't work together according to MSD tech site.

I am using NGK BPR7ES with .9mm gap for several years now.
NGK's seems to be pretty forgiving if you have some fuel flood problems.

3.5 V8 / Viper Hurricane cam / Magnacharger 110 supercharger 7Psi / MSD 6 AL + BTM + Pro Billet / Holley carb.

I've been using NGK BP6E V-grooved plugs -
Rover, 9.35 compression, Offenhauser manifold, Holley 390

With points ignition I was running the recommended
.6mm / .025” gap

I recently installed a Pertronix Ignitor and Flamethrower coil.
Initially I left the plug gaps as they were, and a test drive didn't show much difference.

When I got round to gapping the plugs to
.8mm / .030”
I immediately noticed improved performance, idling & starting

So a tiny change in the gap can make a big difference.. might even try .9mm at some stage.

Hi Ian, i tried the plugs at 0.9mm and found i had a miss, almost the same set up as yours but 3.5

Thanks for the info on the Iridium plugs, I am using a full MSD system so will not be putting them in the engine now.
Reading the MSD tech site is interesting, The techs seem to be on the ball with most stuff including a guy who is doing a cut and shut to shorten his dizzy, interesting reading if you have a bit of time.