Advice Please - Poor Running Series 1 4.2

[AussieEtype]

My neighbour has been rebuilding his 66 Series 1 4.2 and I have been helping him while my car sits in the garage untouched.

He now has the car registered on the road and it starts and initially runs OK. However when the temp gets above 75c (on the gauge) the car starts running rough and looses power.

Carby wise all three have been refurbished with new jets and has been tuned according to the book and O2 sensors as well as double checking the colour of the plugs - all seems OK.

Ignition wise - weights in the dizzy lubricated and seem to work OK, new vacuum advance and is working OK, new points set up correctly, new condensor, new cap and rotor button. New coil and leads.

He has spent a fortune on this car but despite my continually suggesting he spend the equivalent of ?100 and get it put on a modern electronic tuning machine to identify the issue he has refused to do so and is continuing to try self diagnosis without success - has been going on for about 6 weeks.

So I am open to suggestions on what could be causing poor running when starting to get hot.

Thanks

Garry

[abowie]

Few thoughts.
Just for the hell of it, check the compression. You might get a surprise.
Fuel. Check pump pressure is under 3psi, check filters.
Vacuum leak. Get a vac gauge and plumb it into the manifold vac line somewhere. Vac leaks can be a bastard to trace if you don't look.
Make sure that the choke is actually going OFF when you turn it off.

Laugh and drink beer when you still can't fix it and send it to an expert.

[AussieEtype]

Thanks Andrew - compression is fine, all filters and fuel lines are new and seem clear.

I am leaning towards something in the ignition (I once had something similar in my V12 that turned out to be a slightly crushed coil) he is looking at the condenser etc.

Garry

[vacbag]

Garry.
You say a new rotor arm has been fitted but i suggest you try another as Lucas copies are notorious for causing problems.
The suspect ones are a tight fit on the dizzy shaft and once the engine gets to a certain temperature the shaft expands and a hairline crack opens up and the ht tracks to earth causing poor running.
Steve.

[AussieEtype]

Thanks Steve - very good point. I knew that issue applied to Rover V8s (had it with my old V8 Discovery) but did not know it also applied to Jags.

Will get it checked out.

Cheers

Garry

[AussieEtype]

In line with my comment above about a crushed coil in my V12, gave my mate a new Bosch GT40 coil (non ballast) that I had lying around and the problem seemed to have resolved itself. Even the coil he had was brand new from a well know UK supplier it seems it is breaking down when hot.

He is now keen to go electronic ignition but does not want to buy a complete dizzy etc but rather get a kit to convert his current dizzy to electronic, so suggestions on what kits might be suitable would be appreciated.

Cheers

Garry

[mystery type]

he has refused to do so and is continuing to try self diagnosis without success -

I like his style.

If your car is running fine, try swapping bits over (ie. coil, leads, dizzy,etc) until you determine what is at fault.

[AussieEtype]

If your car is running fine, try swapping bits over (ie. coil, leads, dizzy,etc) until you determine what is at fault.

I agree but my car is a V12 so nothing is the same - the coil I gave him goes on a Rover V8.

Hopefully the main issue has now been sorted and if he ultimately goes the electronic route things will also be sorted in the long term.

Cheers

Garry