Thread: v8 missfire

Another mate has a spare distributor with EI he has offered to lend me to test.

Could this be it? What else could it be?

Do the dizzy cap and rotor have "Lucas" on them? If not it is very well known that some cheap rotors go directly to earth through the shaft.

Regards Philip A

Hi Phillip,

Rotor has Lucas written on it.

No writing on cap, but it came in a Lucas box which I still have.

Coil is Bosch

Rgds
Pete

These things can drive you mad, but probably a coincidence that it happened after the clutch change.

I think I would start with the plugs and maybe try another set. its not unknown for a plug to be a dud. Someone posted about this recently with NGK plugs, and missing under load is a common plug failure.

Maybe have the AF ratio tested by someone with a sniffer under load to eliminate the carb.
Regards Philip A

Pete,

Had a similar issue with the new series 3. The plugs were new.

Checked everything, then ran a timing light over each plug lead and found #4 not firing. Swapped #6 and #4 leads, it stayed with #4. Swapped #4 plug with #3 it went to #3. Problem found. It was sparking intermittently, and with so many firing strokes it was hard to pick.

Everything else was also new. It happens sometimes.

Good luck, I want to see you guys out with us on Sunday.

CC

Originally Posted by Psimpson7

Our Stage 1 is annoying me a lot! Any help would be great.

It's a 3.5, with a holley 350, and electronic ignition.

Ok, it was running fine and did about 150km before I pulled the engine to change the clutch.


Early in that 150km or so I changed the following when I serviced it:

• New Ngk plugs
• New HT leads
• New Distributor cap and rotor arm
• Rebuilt carb and reset float level

Now after I put it back together I have a missfire under load and I cannot solve it. It seems to rev fine with no load, although it is a bit wooly until it picks up.

I have so far since the missfire appeared:

• Fitted a new fuel filter.
• checked the fuel supply.
• checked the carb.
• fitted a new coil (thanks Grimace).
• checked the voltage at the +ve terminal of the coil which was @7.3v which I think is fine as its running a ballast resistor, which would suggest the BR is fine too?
• removed, cleaned and refitted plugs.
• removed and refitted every HT lead, double checking firing order.
• Removed, cleaned and refitted earths on engine and battery.
• All related wiring seems fine.
• All vacuum hoses are connected as they should be.

Another mate has a spare distributor with EI he has offered to lend me to test.

Could this be it? What else could it be?

It did seem to be slightly better after I changed the coil.

Why did it suddenly occour after I changed the clutch?!

Cheers
Pete

Pete, this seems to me to be an area to investigate. What jets/ power valve did you fit?

JC

I've just swapped out the distributor, and electronic ignition. (thanks Eric!)

Took it out for a quick test and seems maybe better, but need to adjust the dizzy timing and will test it again tommorow...

Hi Justin,

Sorry I missed your reply yesterday.

The jets are too big, they are 62's but it worked fine for the first week or so so I don't think it is that. At least not the missfire under load bit anyway.

I have had a bit of a play with it with the replacement distributor / EI now and I cant seem to improve it....

Remembering back this is the sort of reason I ended up stopping having old Landies!

May start swapping stuff back I think... plugs/leads/cap/rotor one at a time.....

Rgds
Pete

Are you running a genuine electronic distributor? They should not be run with a ballast resistor. Make sure your coil is a 12V electronic compatible coil and run a new 12V wire from the ignition switch if your ballast is in the loom. It may also be your ignition amplifier, they are a known issue with weakness of spark. The Bosh amp conversion may be on the cards.