Hi all first post first jag,
I purchased a one owner 74 xj6 4.2 which was running well and registered up until 12 months ago when the PO took ill and has been parked for 1year. I changed fluids,spark plugs,some front suspension,steering and other bits like globes etc and got it (mot) registered 2 days ago.
The car has started to run a little rough, so my question is;
Should I start my journey in any methodical way?
Or just start with the obvious things that would effect running such as carbies,filters,distributer,coil.
Any specific niggles to this model would be appreciated.

 

Maaaaate.

Stromberg carbies (hope not), or SU. If SU, which style, HD8, or HS8.

Carbies is always my first stop, balance them, and reset the mixtures, nearly always sorts that engine just fine.

 

I think they are SUs

 

Do the above look familiar Grant?

 

Do they have manual chokes or Automatic enrichment.

https://www.jaguarforums.com/forum/x...t-su-s-111909/

If you go to post #6 of the thread below you will see a PDf with step by step tuning SU's.

https://www.jaguarforums.com/forum/x...17/#post928571

Any parts you need will be available from Home (link to SU Midel, Sydney)

 

They are manual choke. Thanks for the info as I will definitely start with a good clean and overhaul .

 

Yep, HS8.

Clarke has covered it pretty well.

Simply remove the bell chambers, one at a time, and clean ALL the black soot out of them and the peripherils of the pistons.

That is 99% of the issues with them. Setting the float height is possibly not needed at the moment, but setting the mixtures etc as per that PDF will have it sweeten up significantly.

 

HS8....this will be the FIRST of many parts going into my jag memory bank.
Thanks again guys.

 

HAHAHA, memory, then you start drinking, then you forget what you remembered, so you drink some more, get the picture.

Anyway, forget that, just enjoy the Jag.

 

I usually suspect ignition issues in old critters.


Simple test. Run the engine n the dark. Observe the HT leads for a "light show" . Old, dried out an cracked insulation does this. Carbon ore wire seems to be Ok when cold, but when warm, the resistance goes up and a miss comes in.


Examine, and if questionable, replace the spark plugs. At a minimum, clean and regap.


Examine the underside of the distributor cap. Cracks do funny things. Worse when the weather is humid!! Contacts excessively burnt. A little is normal. Check the carbon button in the center. Healthy or beat up?


I have a little tool, I made decades ago. A bent piece of wire enabling a piece of emery cloth to be wrapped in it. I use it to clean the towers on the distributor cap.


And simplist and most fun. a nice drive can awaken a sleeping critter and the miss will just go away.




carl

 

Read the write up on carbies excellent and will do. But as per write up I am checking the plugs first, whilst they are new I just want to check the type and gap..They are NGK BPR5ES 11 and are gapped at .045 in. The owners manual says .025in.......your knowledge would be appreciated .

 

My books recommend Champion N11Y plugs with a gap of .025 inch (0.64mm) for your model. I have fitted (N11YX) with a .025" gap, I had AC Delco R44XLS.
A quick search for NGK Showed BP5ES with a gap of 0.6mm(.023") or an Iridium BPR5EIX with no gap listed.

 

Wrong plugs, FULL STOP.

BP5ES, which is now BP5EY, which has a split centre electrode to aid "Unleaded fuel" igniting down here. True or false????, depends on what you want to believe or are drinking at the time.

Gapped at 0.025" ONLY.

This alone is more than likely your misfire, hesitation.

"R" spec = Resistor plugs are NOT required on carby cars of this vintage.

 

Thanks guys sure seems like the blue slip repairer had no idea. I'll get the correct set and start from there....knew something was not right when the original service book that came with the car states .025 in.

 

Thanks again Clarke and Grant...this morning I fitted a set of champion N11YX and the miss and odd backfire have gone. Now onto the carbies to get a better idle as its sitting around 600rpm at idle when warm....searching on this forum shows 750 is pretty normal....I'll follow clarkes write up and let you know

 

Mine idles around 700 when warm in N and 550-600 in drive. Not exactly to the book but so close it doesn't matter.
I played around with the idle until it is where I am happy, at the settings(not far the book from where I am)

It is all sweet. I assume you gotta go a bit by what feels best to you. It is 40+ years old and could need that little personal touch.

 

Got a feeling there are going to be a few "close and personal" moments with this one........I just luv the look of them.
And I will play "700 ish"

 

Should've said grants write up sorry mate....showing my age!

 

Exactly the exercise I am performing as we speak, just stopped for a bite. Will update with some pics later.



UPDATE
Last time I did this was 4500 miles ago, is this a normal amount of carbon and grime for the miles covered or is there something else here I should address? It was running fine, just the slightest miss when cold at idle.

 

AH, I miss those SU's. Such SIMPLE things.

Pity they wont work on the 3ltr V6, life goes on.