Using a thread cert or whatever, not helicoil. Should be ok.

 

Your choices are an insert or a Helicoil. The one is as good as the other done properly. Spark plugs are inserted at low torque to partially crush the seal washer. Helicoils have a reputation going back longer than most. Both create swarf that should be removed from the cylinder.

 

The threads shouldn't be damaged in the first place. It's not so difficult to install spark plugs. For making a repair, I'd advise Time Sert or similar, where there's space. They are possibly a little extra effort, but can't go too far in and don't have the tang to deal with.

 

We could debate that story all day long without resolution. Time Serts create a lot of swarf. With the head off I might agree they might have some advantages. And I say might.

As you rightfully say there is no excuse for damaging threads. One outlier/exception to that comment is the VW Beetle. Where the plug protrudes into the combustion chamber & a few threads clog with combustion by products. You do thread damage every time you change a plug.

 

Agreed. Basically, it's a no win. You just hope that whatever you do doesn't cause 'collateral damage.'

 

Ok- Just to clarify, I did not strip out the threads. Somebody maybe with a air impact did? The top of the threads are GONE. I use a torque wrench whenever possible. certainly on the plugs.

Engine WILL get a full rebuild in 2023 regardless so any swarf issues will be corrected then.

I dont understand why you would steer me away from adding electronic ignition when ignition is step one in setting the engine to run correctly. (technically a valve adjustment should be first, but hey)

In my mind it is: (as it is with EVERY car I ever restored)
1. Plug hole fix
2. Electronic ignition and new coil
3. Fuel pumps
4. Flush cooling system
5. Rebuild carbs

Where am I wrong here?

 

I would recommend disconnecting the hoses from the radiator and flushing the rad out separately.
Disconnect the heater matrix and again flush it separately.
Then with these two disconnected remove the thermostat and replace the housing. Stick a powerful hose into the heater pipes and flush the engine from them out of the disconnected radiator hoses. Once that is done I would even go so far as to shove the water hose as far into the block as possible to blow out all the crap. You will be amazed at how long it takes before the water starts to run clear.
When you have done the cooling system flush check the core plugs for rust and replace them. They are known to rust from the inside and once you have flushed all the rust out they will leak.

I would never use a torque wrench on spark plugs. I prefer the feel of tightening them by hand as they only need to be nipped tight as they say. I always start a plug by hand so I know there is no chance of the thread being crossed until it is snug and then nip it tight. I use a large box spanner so I can turn the plug in its thread by hand. There is a crush washer on the plug and it is this that you nip up tight at the end. I would not know what torque setting would be used on a spark plug and would not trust my torque wrench to be set low enough.

Valve adjustments on the XK engine are not easy. There are no adjuster screws or nuts it is about changing shims. A shim set costs about £300 and you would also need a good set of feeler gauges and either a good vernier gauge or micrometer. If the engine is quiet I would leave it alone. If you have got a top end ticking noise then yes they might need shimming but I put mine into my local classic Jaguar garage to have mine done and it cost less then buying a shim kit.

 

That's just fine! You are not wrong. Listen to Cass re proper cooling flush & I agree with plugs. You just get that feel of slight give in the crush washer by hand. If you are like my late father was, however, who overtightened everything & I had to go around the house opening taps for my Mom then use a torque wrench on plugs. He should have worked on steam engine drives or bridges etc..

Let someone else set up your tappet clearances that has a bucket full of shims. Alfa with the Sud are the only people that had a civilised system for setting clearances in OHC ~ cam on tappet engines (other than modern zero lash hydraulic tappets). Twin lobes per follower with an Allen key mechanism built into the buckets where you stuck the Allen key in via a hole in the cam between the lobes & took it a few clicks backward or forward to change clearance. Required a twin prong tapered feeler gauge. What a pleasure. Whoever designed that deserves an award. That was real innovation for the era. In fact the whole boxer engine in the Sud was a work of art.

 

I always use a torque wrench on spark plugs.
In aviation it is mandatory and the typical torques for 18 mm plugs range from 25 to 35-foot pounds depending on the engine.
!4 mm aviation plugs as used on early aviation engines like the DeHavilland Gipsy are torqued to 20-foot pounds. I do the same on 14mm car plugs.

Cass's instructions on cleaning out the cooling system are good but I don't agree with trying to replace the core plugs at this stage.
The real "sleeper" core plug is at the back of the block requires engine removal which is not warranted at this stage.

If the tappets are a little rattily don't get too excited. That can be put off while you go after the "need to do" to get the 420 project mobile.

 

Yes ~ That cursed rear welch plug.

 

Thorough flushing of the cooling system is always a good idea and something to repeat every few years with an old system especially of unknown history. Then fill with a full strength coolant mixture, more than 50% antifreeze.

With spark plugs, I like to make sure everything is clean so the screwing in process is as smooth as possible. Before removing the old plugs, clean the valley, blast out the hollows with compressed air or vacuum. After the old plugs are out, vacuum again. Check the plug holes and sealing surface with your little finger, wipe with an oily (but otherwise clean) wash leather. Carefully screw in the new plugs by hand to finger tight - back and forward a bit to be sure they are right. Finally tighten with a suitable plug spanner by a quarter to about a third of a full turn; that's more than 90° up to around 120° and never more than 180°. If you're putting old plugs back, it's good to replace the washer (gasket). However, using the tightening rule, the washers can be reused once or twice.

In general, seals of almost any kind don't need to be crushed to death. Tighten just sufficiently and check later for leaks.

I'd have a good look at the core plugs. Tap them with the handle of a screwdriver. If they seem solid, I would leave them until you can take the engine out (lift the body off the engine) to reach the one facing the bulkhead.

Valve clearances: silence is as big a worry as noise. That is, it's important to have some clearance. A clearance a few thou too wide isn't a big deal for now. Of course, a sticking valve or lifted valve guide are.

 

Bill I would not really recommend changing the core plugs either side or rear with the engine in situ. No room to swing a hammer in the engine bay but after a coolant flush with old core plugs it would be wise to change them if they show signs of weeping. Below are photos of my engine block on rebuild and where the core plugs are situated.

Exhaust side core plugs X3

Inlet side core plugs X3

Rear core plug X1 This was whilst stripping the engine down so old core plug.

This is what you are faced with if you try and do the core plugs with the engine in plus no room due to the inner wing to swing a hammer even if all the exhaust and ancillaries are removed.

 

Cass
Completely understood. I have rebuilt a number of engines and if it is out of the car core plugs (we call them welch pugs) are a standard replacement item.
I recently had to replace a core plug on the right front of a MK1 which I had converted to HD6 carbies. That was due to an excessive pressure developed in the cooling system associated with an alloy radiator and a 1.2 Au (17 PSI cap) supplied . The Jaguar recommended pressure cap is 4 PSI.
I removed the front carby and still could not get a proper swing at the new plug with any sort of hammer.
I resorted to my reciprocating air chisel with a suitably shaped like a hammer face drive bit, and it did the job nicely.
Where there's a will there's a way

 

And thereafter maintain your coolant concentrations. Even if you have to buy a refractometer.

 

Years ago I had a 1964 E Type 3.8. It would get hot and the temp gauge would keep going up no matter what I did when the outside temperature was above about 22°C. In the end the way I cleaned everything was to:
-drain coolant and flush thoroughly with a garden hose. Open the block drain at the left rear to ensure the block is drained.
-fill with a mixture of acetic acid and water. You can use vinegar, I used Kodak Stop Bath simply because I had it and it was cheaper than vinegar.
-Run engine up to temperature, ensuring the thermostat opens and set the heater to hot.
-Let engine cool, and drain acid/water mixture.
-Flush completely with water to remove sludge and acid.
-refill with fresh coolant.

The acid loosened and removed a huge amount of minerals within the block that had come out of the hard water that had been mixed with the coolant. When I drained the water/acid mix it looked like milk. After the cleanign, it ran at thermostat temperature all the time. Simply flushing with a garden hose would not remove the baked on minerals that had deposited inside the block, that had to be removed chemically.

 

@dsnyder586
Hey D, have you done anything to the 420 in the past year? Ever get it on the road?

 

A little. It is running, goes backwards and forwards up the street and will stop if you press the brake pedal. I acquired an XK120 which has dominated my efforts but will get back to the 420 shortly.

 

Great. You are famous, after all. Keeping your fans waiting will create anticipation !!!

Congrats on the 120!

 

Just a ping to let all know I am still here and working on her- She starts on the button now, very happy about that. Will be working on the body this spring and refining the running condition. I'll post pics as I progress.

 

Great to know D! The world needs more 420s. And btw look at the number of posts you've received likes on.