Spark plugs (again)

[Kerryt333]

Hello Jeff,
I believe the previous thread you mentioned was about my +2 ,which appears to be ok now & although it started off as a spark plug question it turned out to be the ballast resistor on the coil was faulty.But going back to plugs ,when I was trying to get mine running properly the Crypton Tune chap I used reckons he goes to lots of classic cars which all appear to need hotter running plugs to ensure burning the fuel efficiently, & he recommended NGK BP5ES plugs for mine which are now fitted, & also using 97 octane ultimate unleaded.I've even put some octane boost in as well, because I believe a lot of problems are caused by the make up of today's petrol compared to the 1970's.
Hope you get it sorted.
Regards
John

[jeff jackson]

Hi John,
So NGKBP5ES must be even hotter than the 6's. You say you are in Dorset, what Crtypton guy did you use? I am in Dorset as well,
if you are happy with the service you got from him, I may well run the elan over to him, with my new NGK 6 in place when they arrive!
Kind regards
Jeff 72+2

[gwiz22]

Hi jeff,

This might sound a little way out for a thread that started with spark plugs. My Plus 2 always seemed to run sooty and regularly fouled the plugs. It seemed to run better on the hotter N9Ys rather than the N7Ys specified in the manual. The engine appeared to be in good nick with 180psi compressions and didn't smoke during normal running but was always a little fluffy on tickover. At one time when I had the air box off I noticed oily vapours coming through the breather tube which connects the head to the carb backplate.
I didn't pay any attention to this at the time and carried on enjoying the car.

Because the engine was leaking oil I decided to remove it, strip it down and fit new gaskets and seals. I wasn't expecting to do any overhaul work as the compressions were good and according to the previous owner the engine had been reconditioned and the car had only done around 6,000 miles since then. When I got the head off I noticed it was quite coked up with black carbon, so I decided to clean it all up. This involved removing the valves. To my surprise the valves we quite sloppy in their guides. All of a sudden everything fell into place. Running sooty, fouling plugs, back pressure from the head. I surmised that with the addition play in the guides, the pressure was slipping past them on the upward stroke while the valve was open and pressurising the head, leading to the oily vapours exiting into the carb airbox.

I am at the moment in the middle of replacing the guides and do not have the engine back in the car so cannot confirm my diagnosis is correct yet until I get it running again.
If you think about it, your poor starting could be due to oil running down the guides when the engine is standing and therefore making it hard for the plugs to fire from cold.

It might be worth taking the air box off and check for pressure coming out of the head breather tube.

As I said at the beginning, a bit way out but as you seemed to have checked most other things, then maybe, just maybe.

Good luck and I hope you get it sorted.

Regards
Graham

[Kerryt333]

Hi Jeff,
I'm in Winterbourne Steepleton, 4 miles out of Dorchester towards Bridport direction.
I used Richard Miller in Weymouth who trades as Crypton Tune I think, I have his number at work & will send it to you tomorrow.
Where are you in Dorset?
Regards
John

[rgh0]

If you need to go to a hotter BP5ES plug to try to stop them sooting up and causing hard starting when cold then you probably have a base case problem with the carb set up and need to fix that. If carbs are correctly tuned a BP6ES plug should be fine for normal everyday driving and a BP7ES will probably be to cold a plug

regards
Rohan

[Kerryt333]

Hi Jeff,
Richard Miller, trading as Crypton Tune, on 01305 784106 or 07836 594258 is the one I used.
Regards,
John

[jeff jackson]

Hi John,
Thanks for the phone numbers. I'm in Poole so about an hour away from Weymouth.

Kind regards
Jeff

[jeff jackson]

Hi all,
Thanks for all the advice WRT Spark plugs. I have fitted NGKBPR6ES and run the car around for about 30 miles.
I pulled the plugs out, and the tips are biscuit, but the bases around the electrode and where the thread ends are still a bit sooty.
I think I may be almost there......but I am now developing spitting back from the carbs and horrible flat spots.
I feel a new thread coming on.
But before that happens, I have checked for air leaks, and as far as I can tell, I am not leaking air into the system through either the headlight vacuum or the servo vacuum. I wasn't spitting before I started to fiddle with the carbs, and plugs.
So here is what I have done so far, New plugs, checked float and droop level measurements for the D'ellortos, set to 15mm float, and 25 mm droop.
The flat spots bother me. when the car is warming up, it runs pretty good, accelerating, through the range, it's when it gets hot that the flat spots appear. Could this be fuel vapourising? Electrical?
I really need to put some proper diagnostics on this car, preferrably on a rolling road.
I know it's a 39 year old Lotus, but it's beginning to become a bit depressing.

Any thoughts gratefully recieved.
Kind regards
Jeff