Sportster missfire in cylinder 1 and 8.

[Sven]

My Rover Sportster V8 suddenly started to missfire in cylinder 1 and 8 only when reaching about 2000 rpm. I have changed to new coil, plugs and cables. The distributer is a Mallory 27, 2points with vacum. To locate the missfire I used a test lamp (stroboscope).
Greatful for any ideas.
Sven

[greyV8pete]

Re: Sportster missfire in cylinder 1 and 8.

My Rover Sportster V8 suddenly started to missfire in cylinder 1 and 8 only when reaching about 2000 rpm. I have changed to new coil, plugs and cables. The distributer is a Mallory 27, 2points with vacum. To locate the missfire I used a test lamp (stroboscope).
Greatful for any ideas.
Sven

Distributor caps are a favourite for this type of failure on the stock Rover distributor. May be the cause on your Mallory one although I am not familiar with that one. Can you borrow a known good one and see if it cures the problem? If u/s avoid aftermarket and buy OE replacement parts. Don't forget to ID the plug leads before removing them all at once!

The routing of the plug leads across the distributor cap is critical to avoid cross firing. That may be your problem? Pic attached.

Does your set up have an ignition amp module? I have had two fail on my 3.9i V8. It's a known weakness for the Rover item. However that gives a sudden total ignition hesitation when you suddenly accelerate which is a bit unnerving if you are overtaking!
Peter.

Rover V8 Plug Leads.jpg

[Sven]

Re: Sportster missfire in cylinder 1 and 8.

Thank you Peter, think I came close to the problem with your advises. I have to find a new cap and points. Until then I have to run with a rasped one. I have no ignition amp module, what is that for.
I am running a 3.9l with a Weber (Holly) 500. Maybe too big?
Sven

[greyV8pete]

Re: Sportster missfire in cylinder 1 and 8.

Thank you Peter, think I came close to the problem with your advises. I have to find a new cap and points. Until then I have to run with a rasped one. I have no ignition amp module, what is that for.
I am running a 3.9l with a Weber (Holly) 500. Maybe too big?
Sven

Hi Sven.

The ignition amp is used with the Lucas distributor. It also has a weakness due to a poor component in the circuitry. I bought a performance Ignition amp from RPI engineering which was supposed to solve that problem. Unfortunately it would not work with my immobiliser for some reason so I went back to the Lucas setup.

As no 1 & 8 plug leads are next to each other I would immediately suspect a cracked cap. Another common cause is arcing between the two contacts inside the cap, or earthing down to the case. This is usually caused by dirt (or carbon dust from the centre contact) providing a path for the HT voltage to jump across. Once that happens and there is a “burn” mark it’s almost impossible to cure, hence the need for a new cap. As a regular service procedure I always spray WD40 or similar inside distributor caps and then thoroughly wipe it all out with a clean rag to avoid this happening.

You may find the following link interesting, especially the suggestion to avoid the Mallory Dual Points Distributor with Rover V8 engines! Peter.

http://www.gomog.com/allmorgan/MalloryUnilite.html