so, at the moment it looks as if your gearbox problem isn’t really a problem. Just to make all the necessary confirmations, you might check the engine (4.2l), the gearbox (BW65) and the diff (either 3.31 or 3.07; the diff ratio is stated on a metal tag attached and expressed by the gear ratios, like “43/13”). Mine makes around 110 kph @ 3000 RPM with a 3.31 diff - I think later on during SII production Jaguar changed to 3.07 diffs as standard equipment for Germany as too many German drivers caused too many sudden engine deaths on the motorway …
As for the engine: There are many things you can test statically like compression, timing, fuel delivery, false air, all of which may influence performance in the higher revolution area. One favorite is two spark plug leads mixed up, another is a cylinder not co-operating because of leaning out (check plug colour).
If this is all o.k. you might just change the oils and gradually take the car to regular running. I’d be concerned about too big chunks of carbon working loose as well, so play it cool. At the end, however, the engine should pull up to 5000 RPM without troublesome noises and then the box should shift …
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Sometimes one gets away with ‘rushing’ a lazily driven engine, Ignacio - and sometimes not…
As the engine is already out of the car(?) some test that should have been done first can’t be. A compression test would have been pertinent - it might have shown what to look for when the head is removed. Unless damage is observed; you just have to do a full valve job - particularly verifying that the valve stems are straight…
You seem to be in good, though likely expensive, hands - but frankly; I don’t really like repairs without basic testing confirming specific faults. Engine misbehaviour as described should first be followed up by a compression test; if test fails it would largely explain all symptoms shown - pursuing other faults with failed compression is likely wasted…
3500 rpms at 90 - 100 kph is a transmission issue - and the fluid level should have been checked before further work. It may simply be that the box stayed, or dropped, in 2nd gear due to a fluid level issue. Downshift at speed may indeed cause jerking - and suddenly depressing the gas pedal may/will indeed cause a downshift - it is meant to. Staying the 2nd with the pedal lifted is not…
Anyway, work done on carbs etc is not necessarily wasted - it may just be unnecessary…
Thanks for the guidance, Frank.
Engine is not yet dismounted, but it will be next week.
We have been told too many lies from the beginning, as I could lerant yesterday. I informed the seller about each step, as he was quite emotionally atttached to the car. When I explained that the engine had to come off, he “remembered” that it was twice overhauled.in 73k km!! He just forgot. Once due to overheating when a cooling hose got opened while driving… but he could barely remember what wad.wrong. Secondly, due to “adding Wynns to the oil”… and a piston had to be repaired… and the head overhauled"!!
God.knows…
My first action was to ask the workshop he used to bring the car to and thry diverted me to the former Jaguar mechanic who check the compression and told me the three forward cylinders had less pressure at idle… so fwd carburetors or valvea overlapped, springs broken… but he didnt want to even touch it!!!
From there to my well trusted mechanic, who started by the easy thing: fixing the carbs to find out more from there. And then it was when the.impossibility to run at a steady idle plus the strange noise showrd him the chain pad out loosen… plus the gearbox, with new.fluid, .provoked an oily pinky spill on hia workshop floor. The kickdown cable penetration hadn’t its ring, but a coverage of filler.
The car looks new.inside and outside (“never repainted”, but actually it has), but mechanically it has been neglected.
We"ll fully dismount heads, check valves, lap seats, renew.ancilleries and chech crankshaft bearings, pistons…
Btw, the engine jerking was just when passing from 90kph to 100. Not when decelerating or breaking.
It was the engine. I presume gearbox is fine… but the engine requires a serious repair. I wish we could know better, as you suggest, all we have to do, but maybe we started wrongly and based on lies or wrong info.
I Thank you All for helping and follow this long post and “heavy” info. And I also apologise for my poor English. I will soon get back with the next chapter of “how to survive a wrong start in Jags”.
Cheers,
I ran a v12 and a xj6 out of Jijona for many years. The advice I was given by someone who fixes and races these cars was that the valve seats were not an issue with unleaded fuel. Overheating a v12 will likely cause dropped seats though. Someone else might comment on the 6 cylinder. My xj6C had a 4 speed manual box with overdrive by the way.
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Firstly, Ignacio; compression test are not done with the engine idling - you must have misunderstood him…?
Please, please ask them to do a compression test, before doing anything else - it’s very straight forward on the 6. It will conclusively tell if there is valve damage - which of course requires head removal. If the compression is even and above some 120 psi there is no valve damage - though a failed compression test indicates faults that requires head removal in any case…
However; they should also check the valve timing, also easy on the 6 with the valve covers removed. Slack chains will rattle - and slack is easily detectable. Chain tension is adjustable, and while the chain set-up is well nigh indestructible; it’s advisable to check valve timing to see if a slack chain may have jumped sprocket teeth. Which almost invariably leads to bent valves - and a failed compression test…
The main point is simply to glean information before dismantling - to better know what to look for, and a possible cause of whatever fault you may find. Which may avoid a repeat…
So far, the attempts of a fix appears ineffective - likely due to ‘we started wrongly and based on lies or wrong info’. So starting out the right way; compression test may clarify matters…
The salient points is; 3500 rpm at 90 - 100 kph is not an engine problem as such. Importantly; if the downshift cable’s attachment to the box is incorrect - the shift points are completely haywire. In this case; the box probably never went out of 2nd - which will perfectly explain 3500 rpms at 90 - 100 kph…
…and forcing an ‘unprepared’ engine to such high revs; it may show displeasure. 3500 rpms is of course normally no big deal for the xk, and to assume that the engine is seriously damaged without further testing is jumping to conclusions!
Compression test, compression test, compression test! Then go on from there…
Your English is certainly not ‘poor’ - but your Jaguar knowledge needs some honing…
Thanks a lot.
Your post has been printed and I’ll visit the workshop with it in my hands.
I want to see everything and take pics of every detail.
I remember the three shifts working well, so I think the gearbox works correctly… but also the engine detoned at over 90kph, so today I’m more inclined to believe that the engine itself was the root of all the problems.
I’ll keep you posted about the progress and let’s see the performance when the engine is repaired.
No chance to do a compression test any more, since the mechanic showed me pieces of the timing (bolts, springs, pad)… that were loose or had been dismounted. We’ll have to open , check, measure, revise valve stems, seats… a pity.
This guy has a lot of experience with classic Jaguars and I do trust his way of working. A pity, however, the test wasn’t done. I’ll ask him the reaosn not to have done it before.
Now… not to bother anyone more, I attach a pic of the car, with the hope we’ll soon get it performing as nicely as it looks. **** Sorry… no chance, I guess the reason is related to the low priviledges to just-joined members.
Best regards,
I really should read through again before posting… but I wondering if hesitation at certain speed / RPM could be due to fuel starvation or a distributor problem.
Fuel - check filter, pumps et cetera.
Distributor - potentially the initial timing is fine but the distributor is not advancing correctly. Also, if not idling correctly, I would begin by checking the vacuum, distributor and then the carbs (although I am not a trained mechanic). Of course, as mentioned, best to start with a compression test to get a feel for the general condition of the pistons / cylinders / head.
Furthermore, are you using the original tachometer and speedometer to inform you of the RPM’s to Speed ratio? Mine are quite inaccurate and it could well be that your speedo is showing under and tachometer over. Speed can be tested with a phone app (when driving) but the tachometer will require a specialised timing gun with a digital tachometer (or find a cheap digital tach you can wire up).
Hope it all works out, keep the faith, very very cool cars when you iron out a few problems and get to know them!
Thanks lot, Edward!
Any idea is welcome.
To me, in spite of the few driving I could “enjoy”, the problem was not an unsteady idle, but too “metallic” and noisy (I thought it was due to the tappets, but now it looks like the chains were not tighten enough).
The speed reading seemed to be correct, so I don’t think the tacho/speedo was not offering good info.
It could be a problem with the distributor, as some pistons could have been failing… but at this stage, after a lot of hidden info, or simply lies, I think we should check it all.
I wonder is an engine is not burning well, one or two cylinders are “out” or low performing, carburettors also not working well, distributor/plugs not igniting at its correct moment, etc. I wonder if this would cause detonations and low rpm/power rate, However, I see everyone states that the rate speed/rpm only depends on the transmission… I still believe the engine was not giving the output it should and, when accelerating, it just detoned and jerked, so… I drove it straight to the workshop.
I also believe that Frank was right with regard to the adjusting of the kickdown cable.
I regret I cannot attach a pic. It looks great. I just believe the maintenance has been totally neglected for years.
For the time being, we have renewed the ball joints, all the bushes by a polyethylene kit, rebuilt the carbs and all the rest is to be checked.
I thank you All for the continuous support and kind suggestions I’ll obviosuly consider and follow.
Best regards,
…it just means that a wider search than perhaps necessary is required. If all, or most, valve stems are bent it would indicate a valve timing issue - one or two stems bent points to a spring problem. Corresponding dent marks on the pistons may or may not be visible. But if the valve stems are straight and pistons intact; the plot thickens - and with no previous testing clues are few…
No matter what damage to the engine; excessive rpms to road speed will not ensue…
With an XK engine having undergone major, but undefined work already twice in the past and another piecemeal approach (timing, head, what else?) coming up I’d fear a never ending story.
Dear All,
Merry Xmas and Happy New Year!!! I hope you are all enjoying these days a lot.
Going back to the topic, the news are depressing: ovalization in the cylinders… which means we’ll have to machine the block and install oversized pistons. Not to talk about other needs (heads, timing, crankshaft bearings…). We can see a major decolorization iwo two cylinders, cylinder heads partially burnt and marks left by the cylinders in the blocks only in 50% of the surface… awful.
As the old seller recently remembered: “I forgot to tell you we had twice problems with two cylinders many years ago”.
No more complains: two options, a restored engine (please suggest reliable suppliers) or major overhaul.
Terribly expensive options anyway.
What I want to avoid is a second hand engine that might suffer from similar problems.
Feel free to post.
Challenging project in sight!
Best regards,
I had to do two engine overhauls on other cars and always found a way to find a fixed price arrangement which I never regretted. It seems to be difficult though to find something similar for the Jag engine.
Of course, there is no guarantee that this will be it, but with some luck and a few hours of work you’ll end up with a more powerful engine and more than enough time bought for a serious overhaul of your original engine.
If you want, you can pm me and I can help you out shopping German or Swiss websites. UK sources may be more plentiful, but transportation is a lot more difficult and expensive over the channel.
Hi, Jochen!
Happy New Year!
Not sure about how to pm. If I just cannot (not enough priviledges) or just a bit clumpsy.
Thus, openly, please send me any contact of specialists in Germany, Switzerland…
I hope I can find something in good condition at a reasonable price. For the time being, I’ve just started to ask dealers who offer guaranteed rebuilt engines, but prices today are quoted quite high.
Best regards,
Ignacio, click on Jochens picture, this opens a window, on the top right there should be a blue ‘message’ box, if there is you can private message from that point, if not, as you say you may not have the privilege just yet.
I’m not sure what determines that protocol.
In the process of rebuilding the 4.2 engine now… (new liners - until recently I thought the engine hadn’t them, new pistons, bearings, timing chain, pumps, electronic distributor, valves, head ancilleries…).
Anyone has experience with “enhanced oil pumps”? I have been offered the standard or the enhanced one and not sure if it is worths the price and what difference in lubrication performance it offers.
Thanks,
