Spark plugs Dolomite Sprint

[Paul Roberts]

Hi all

Starting to get organised for a couple of comp events in October. One problem I have with the Silver Sprint is plug fouling with idling and slow running (ie queuing for events). Car is running 45 Webers with Neuman tarmac rally cam. Nothing more frustrating than the first part of a hillclimb run or similar being ruined by the car not pulling cleanly until the plugs have cleared. At the moment using NGK BP6EF (I think that's right). I change them so often that I may as well spend some more money at the outset and go for a better plug that hopefully overcomes this problem. Curious to hear if anyone has advice or experience with the NGK Iridium IX plugs (or similar) and exactly what number I should be looking for.

Thanks for any advice

Paul Roberts
Perth, Western Australia

[gmsclassics]

Hi Paul
I've run NGK BP7EFS for years on my circuit race car with no issues at all. I change every season. Running magnetronic the gap is set at 30 thou.

A hotter plug BP5EFS would be indicated for lower engine temperatures and fouling plugs. You could try those for short hillclimbs but I would be concerned about using those on longer runs if the colour of the existing plugs is okay after normal running.

I recently listened in on a conversation at the track about normal vs long life type plugs (iridium was mentioned). The consensus of opinion was stick with standard plugs - something about they will destroy themselves if something goes wrong whereas the long life ones will carry on resulting in more damage to the engine. The physics/engineering of all this is beyond me but many of these guys have been racing for years so I repeat it for what it is worth

Is your issue about idle jet settings on the carb and the transition to the main jet? Does the problem resolve with frequent 'idling' at say 2000? That is rpm I warm my engine through to full operating temperature before each race - to when the fan comes on. I'll sit at 4000 for 30 seconds prior to lights going out on the start line.

Hope this is of some help

Geoff

[Mad Mart]

I've been using NGK BP6EFS on my track Sprint for about 10 years with no probs (25 thou). The last few years I have been running a Megajolt system with the plug gap set to 35 thou.

[Dolly-Nut]

I have Webers on my Sprint with Iridium plugs and even they foul if the car is started and stopped a lot/left idling. A lot of it is to do with the idle mixture. A BP6EFS is what a Sprint should be using but there's no harm in using a 5 if you're having problems. IMO iridium plugs are overpriced. The bigger the plug gap the less likely they are to foul, mine is on 0.040" which is the ideal limit.

[trackerjack]

I used to change plugs about every 3k in my Dellorto 45 Sprint as unless the plugs were new it would develop a misfire if left idling too long.
Oh Piranha ignition BTW.