Thread: Spark plugs and Rover V8 Misfire

G’day all!

My 3.5L V8 County running on both LPG and petrol has a miss from around 1000-2000rpm. The misfire is more obvious when running on LPG, which makes me think it may be an ignition issue (also the motor has recently been rebuilt and the misfire was apparent before and after the rebuild). I have a Lumenition Optronic ignition kit, and the distributer has been rebuilt to suit LPG.

The ignition leads (8mm silicone type) are a few years old but seem fine (all resistances are within limits, no arcing anywhere, no crossed leads etc). I’ve tried a range of coils and cleaned the distributer cap (aftermarket type) but the misfire is still there. This leaves the spark plugs. They are Bosch Super ro468 units gapped at 28 thou and are at the very least two years/20,000 old, but they look almost new with no wear on the centre and ground electrodes.

So is there any way that spark plugs can wear out even though the electrodes don’t look worn?

If the problem does end up being the spark plugs, can anyone recommend a suitable plug? (I have a high compression 3.5L V8). Are the NGK BPR5ES or BPR5EY (the one with the groove in the centre electrode) plugs the ones to use? I’m not too keen on using the platinum or iridium type plugs due to price.

Thank you!

Edward

Originally Posted by I Love My Landy!

Thank you all for your help! I will look into getting a set of those NGK BPR6ES plugs and new leads.

Yes you're right Armadillo those chopper blades are very fragile. I always keep a spare and it has come in handy!

Cheers!

Edward

I've read somewhere on here that aftermarket dizzy caps can cause problems so maybe try a guinune cap first and go fromthere. Bob