XJ6 Series 1 Running rich on front three cylinders

Started By: on 2016-08-21 00:00:00

Recently purchased a lovely 1970 XJ6 Series 1, Need some help on a running issue.

Problem: The front three cylinders are running rich; spark plugs foul up after 50 miles. Back 3 plugs are ok.

Car has WEBER 38 DGAS. Been on the car for a few years. Carbs have been serviced, new gaskets, jets. Plugs leads replaced. Distributor cap replaced. Compression on all cylinders is good between 115 and 121 PSI. When plugs cleaned car runs really well.

I have swapped the carbs around to eliminate the carb and the problem stayed with the front 3 cylinders.

Any ideas?

Thanks Kevin


Just closing this comment out, had a vacuum leak at the firewall end inlet manifold. Manifold gasket changed and a bit more work on the webers and all good now

Like to change the dual points over to an electronic ignition in my 1970 XJ6 4.2 4sp+OD.
Any advice for the system that works best in these?
I understand this is a pretty rare car. Quite a few standars in Europe, but most are 3.8
and all 4.2 in NA are automatics?
Thank you,