spark plugs

[Kerryt333]

Which spark plugs do you find last best in Lotus twin cams?
Regards
John

[elancoupe]

NGK has worked best for me.

[bcmc33]

In standard trim NGK BP6ES or BP7ES.
If you have electronic ignition NGK BPR6ES or BPR7ES.

You could go even better with NGK Iridium plugs BPR6EIX or BPR7EIX.

[Kerryt333]

Hi Brian,
I have tried NGK BPR6's &7's& the standard ones but on each occasion the car runs really well for 10-15 miles,seems OK when it is switched off,but the next time I take it out it starts to missfire& run on only 2-3 cylinders or won't start at all.If I then put anew set of plugs in it starts first go & runs really well until the next time it blows the plugs. I'm wondering if there is something wrong on the ignition side that is affecting the plugs or maybe too much fuel.
Does anybody else get through sets of plugs for a pastime?
John

[Craig Elliott]

I've found that BP6ES are much less prone to fouling up than 7s (unsurprisingly) - sometimes the fuel additive can make a difference if you use one (I used to find that valvemaster + used to make BP7ES plugs sooty very quickly when driving around town etc). Other additives weren't so bad but this doesn't seem to be a problem with the hotter (?) plugs.

C

[Kerryt333]

Hi Craig
My +2 has been converted for unleaded, so there's no additive involved. The reason for me questioning about plugs is that back in 1974 I had a 1972 +2S130 which I used as my everyday car for about9 months, in which time I never replaced the plugs & it started first time every time. Could it be that I need to use the car more regularly?
John

[Craig Elliott]

It shouldn't foul the plugs like that so perhaps a hotter plug type would help. Otherwise I'd guess it's running rich so checking the carb set up may be the next option. What do the plugs look like when it starts misfiring?

Craig

[Kerryt333]

Craig,
Plugs are very sooty & occasionally appear to be wet,excess fuel I guess.
I just don't understand why it behaves so differently than in 1974,maybe the +2 I had then was reasonably new and possibly plugs were better then.
I've been looking at old threads on the forum & will try a few things from them.
John

[m750rider]

It sounds like you are running too rich. Needles and jets wear over time and will result in exactly what you have described. Rebuild the carbs.

[Craig Elliott]

Aside from any issues with wear in the carbs, remember that the fuel available now is very different from the 5 star that was available back then - different octane ratings, additives (inc lead) etc...

Craig

[Kerryt333]

Thanks for all replies.
I will post further news as & when.
John

[terryp]

John
Check the needle valves , and replace with viton tipped. make sure they are set to the correct dimension. NGKBP6ES are the ones for normal everyday poodling around and will not stay sooted up
On the two elan +2's that I have had , both had exactly your symptoms on purchase and both were easily fixed as above

Good Luck
Terry

[Kerryt333]

I replaced the needle valves with Viton tipped ones,as Terry suggested, along with new idle screws & set float levels & new set of NGK BP6es plugs.I had the carbs balanced & tuned & it appeared to be running well, took it for a blast down the road & it revved right through the range,but when we got back & it idled for 2 minutes it went back to 3 cylinders.The Crypton Tune bloke who did the carbs recommended going to NGK BP5es & getting some ultimate unleaded fuel.
So I got the plugs & fuel & took the car out tonight & it was the smoothest it has ever been, until the ignition light came on for about 5 seconds just approaching a roundabout at which I had to stop,upon take off the car coughed a bit but continued up to the next roundabout where it just stopped.It would fire on cranking but would not start, only way I could get it to run was to keep the key held in the cranking position & accelerate then crank it again when it slowed down.Every time I released the key to the run position it died.I managed to get it home by this method, God knows what I've done to the starter motor & ring gear but it will only start by holding the key on cranking.
Electrics are not one of my strong subjects ,so any ideas would be greatly appreciated.
Coil,starter solenoid,ignition switch are my immediate thoughts.
Thanks in advance
John

[stugilmour]

John, definitely check the ignition switch, to at least eliminate it as a problem. Mine failed the other way around; would only fire when I let the key back to the run position and would not fire when cranking. You could just use a jumper wire from the main power lead to the ignition switch (typically brown) to the run position (typically white). Check your wiring diagram or confirm here if not sure.

Other thought. Is your car equipped with the slide switch in the glove box that prevents it from starting? I removed mine during my re-wire, but they can go dodgy.

Note you may have more than one issue going on at the same time.

HTH

[UAB807F]

The coil comes to mind as a possible culprit, although I'd hot wire the ignition as already suggested to eliminate the switch.

Are you on contact breaker or electronic ignition ? If you're on the original ignition, check the state of the points for burning, the condensor might be another source of mis-firing. The other thing I'd check is the state of the rotor arm/internal contacts on the distributor cap, again for burning. Electronic ignition I'm no help with, it's just little boxes to me - if there's no spark at the sharp end, I'm stuck.

The standard ignition isn't too complex, you just need a logical approach (which admittedly seems hard when you're up against it ! ). I make a check list to stop me from just picking at things randomly, starting from the plugs backwards and tick them off as I check. Plugs/caps/HT leads/Coil HT lead/Coil/Distributor cap/Rotor arm/points/condensor/distributor wiring/coil LT wires/etc.