Hi, just a couple of basic questions.
I have been told by two mechanics to run different fuels, one said 91 octane and the other 98. you guys will know whats best, neither of them (both friends) have much experience with pre 80's cars as they have always worked in Dealerships of new jap cars since late 80's.
The other question is should I be running a lead replacement in the fuel, I always do on my older bikes. (4.2 xk engine)

Clarke

 

Assuming there are no known problems with the ignition timing (like being too far advanced) or engine (like excessive carbon build up) just run the 91 and see what happens. It may run prefectly well.

If you get pinging/pinking, try the 98 and see what happens.

The only purpose of higher octane is to get rid of pinging.

You shouldn't need a lead additive. All Jag engines (at least since the late 60s) have hardened valve seats.

Cheers
DD

 

+1.

I run our 98 in all mine, always have. Based on the "old days" when our Super was 98ish octane, and thats what we used in nearly every Aussie car.

Our Standard of that same era was 89ish from memory.

Stay away from the blends (Ethanol), which will be hard in Qld.

 

+1 Grant

Ran "super" since the late 60s - except for the later racing V12s which gulped the special stuff.

This "super" may have equated to 95 octane in the early days, but BP was famous among Jag and racing enthusiasts for its hyper-octane additives. Ever since 98 octane became widely available, we have used it exclusively - from our highly modded 3.0L (ex 2.4) through 4.2L E-Type (and all others in my sig). Never saw any reason to short change these beautiful engines which, for their eras, had fairly high compression ratios.

I am taxing my memory here o1xjr, but suspect your 4.2 XK would be running 9:1 so I would be reluctant to use less than 95 and prefer 98.

Best wishes.
.

 

Thanks for the info on fuel, I'm running 98 at the moment. I think the timing is too far advanced as it over runs when turning it off(stops best by pulling choke as I turn off key)
I have retired mechanic across the road who is going to check timing and give the carbs a once over when we have spare day at the same time, we were just waiting for my service manual to arrive.
Idles a bit rough,but runs smooth. Getting around 20L/100km ,is that in the ballpark?

Clarke

 

Um, 20l/10km is even too much for a carby V12, with Fangio thrashing the pants off it.

Our S2 4.2L BW65 Daimler, averaged about 16L/100km around the burbs, and 13ish on our very frequent interstate runs.

The XJ-S HE averaged 15ish around town, and 11.2 on the last run to Cairns then to Darwin and back home.

 

Agreed from here also ... 11 (steady open road), 12-13 (average), 15-18 (city) L/100K would be my expectation. Living opposite retired mechanic sounds a big bonus - especially if he loves the classics. Can I offer small words of advice ...

Before pulling out the fiddly spanners and 3ft length of plastic tubing to tune those SUs, read up on "why and how" in your workshop manual. Then do it by the book ... starting with all the other engine sub-systems ... then, the air pistons and springs. Over the years, I have been amazed how many had mismatched springs or needles - many had needles not correctly seated in their pistons - let alone the many more with fuel jets incorrectly centred with needles. If you then adapt your method over coming years ... fine ... but start with the recommended method.

As you see, once learnt, even tuning the triples becomes a skill you will retain forever ... I know ... I still have my 3ft plastic tube ...

Best wishes
.

 

Hi, Will be having a good read of the Bently XJ6 series 1 manual. The mechanic across the road wanted to see it before he played around. And yes, he loves his classics. He still works on a lot of VW beetles and combis,old porsche's etc but they are mainly weber carbs I think.
New problem today,temp gauge not working all the time,on and off inconsistantly.
Tried different gauge,same result. Unplugged from sender and gauge, wiring is all good with multi meter. put 12 v to sender end of cable and gauge was heading for "hot". Connect it back to sender and gauge not working,headed off on the afternoon school run and gauge worked for a bit then stopped, I'm guessing replace sender first as it worked agian with 12v fed directly to it.

Thanks again for all the advice you three have given so far,no doubt I will be back many more times.

Clarke

 

Hmmm ... Wish I had wiring diagram to check this, but I would have expected the temp gauge sender to be a single terminal type ... in which case, I would have thought it "earth seeking" ... varying its internal resistance to ground (earth) according to temp. Trusting my memory, you may find that one side of the gauge is powered via a voltage stabilizer, so be careful where you are applying +12VDC until you can check the wiring diagrams.

In any event, most common failure is sender "open circuit" whereby gauge falls to zero - yours may be intermittent but going - so your plan to replace the sender is a low cost smart move. If problem persists ... then please start a new thread with suitable title.

Best wishes Clarke, but keep us posted with results.
.

 

Hi Ken, yes it is single terminal. I just took the wire off the sender and jumped 12v to it to see if the gauge would move at all,it went straight towards hot and removed the 12v before I did any damage hopefully. But I have 2 spare temp gauges that work so took the chance.
Last week it dropped to zero a couple of times,now its doing it more often than not. Sourcing a sender tomorrow,if repco or supercheap don't have one I can get one on ebay for $20.
Gauge was still working properly tonight when I went to get fuel so not damaged I think.
If sender doe's not fix this I will post a new thread.

Cheers,Clarke