engine misfiring

[Eric R]

engine runs well normally but hesitates and mis-fires on quick acceleration or as soon as under load - then the car bucks like a stallion!
Carburetter professionally restored, new rotor arm and distributor cap previously installed, points spot-on all to no avail.
If i replaced all the leads and plugs, are there modern replacements like carbon leads which will perform any better?
If the engine "breathing" becomes blocked is it sufficient to remove the oil filler and rear breather caps to clean the gauze areas, and if so, how best achieved - wash out in petrol and wire-brush?

[Phil Nottingham]

Cleaning the breathers with paraffin (not petrol!) is the accepted way. This should not cause missfiring on a old 3 Litre unless you have terminal piston/bore problems.

Bad missfiring under load is either burnt exahust valve usually no 5 or 6 or weak mixture caused by air leak

Check dizzy earth lead is not shorting when base plate moves vacuum advance. I hope teh condensor was replaced too!

[Eric R]

There appears to be 100s of condensors - do we have part number? and what about replacing leads - have they become specialist parts?

[Phil Nottingham]

It depends what Dizzy you have DMBZ6?

The leads and be made up or bought made or off Ebay from time to time as OE. To make your own see

www.vehicle-wiring-products.eu/VWP-onlinestore/home/homepage.php

Even if you have a later dizzy fitted the 25D6 its condensor will fit and these aere used on the really common 25D4 dizzy for Mini's Hillmans etc and Halfords stock them for a couple of £'s just do not mention "P4" just ask for a 1978 Mini 1100 with Lucas dizzy

[Eric R]

Users manual states dizzy to be DMBZ.6A. Will need to verify this and then check the other items you mention Phil.

[Phil Nottingham]

It will say type on it - and is standard fit for the time - later ones (which are not as good!) will fit though and are often substituted

The later type has a plastic slide out LT terminal in its side