V12 repair by rookie - piston rings etc

Hello jagies !

This is my first post and i hope i’m doing everything correctly. I’m a 95% novice - please be understandingly.
Wheres my matching number engine waits somewhere (to long to explain) I purchased a backup from a XJ Series 1 complete with converter and automatic gearbox which is now placed in my garden :smiley:
I made sure the engine was revolving both with wrench and afterwards with the starter but the compression test showed:
A-Side 9.7-0.0-9.5-9.7-8.7-10
B-Side 10.3-9.7-8.0-10.3-10
As the engine was not expensive painted blue and me very curious I decided to strip it down and when failing at least i had some spares :stuck_out_tongue:
First i had a look with a cheap endoscope camera but the head looked good to me (as a novice). So i stripped the top stuff documenting every step with a picture … Now both heads are off (together with CAM shaft) and for:

  • valves and pistons look good
  • liners look good (no burr)
  • liner A2 had a little rust below the combustion chamber (see picture attached)
  • all together i think that the piston rings might be the problem ?

What would you suggest and how should i access the piston rings (pull the liner or the piston ?) ?
Should i have a look at the crankshaft before ?
On the one hand I don’t want to spend too much on this engine (as its not an XKE engine …) but on the other it would be nice seeing it run again. I know i would have to find a solution for the oil sump and water pump then.

Please help !

Hi Tom , from what I can see the engine looks reasonably good! The head gasket is not too eaten away. Quite difficult to see degree of bore wear from your photo.you can pull the pistons out separately from the liners but you may find that the liners will move off the block face unless you clamp them down.you have two choices clamp liners in situ or remove pistons and liners. Either way Mark position of each on removal as they won’t be numbered if standard works engine.its best to get liners measured for bore wear. They are reusable if less than 0.001" wear . You’ll need to get the pistons vapour cleaned making sure all ring grooves are completely clean.
Head skim should always be done before reassembly, but check valve guides for wear also bucket tappets/ tappet block bores.
Hope this helps
s[quote=“myJagV12, post:1, topic:353794”]

Hi Nigel, thx for your informative answer.
So first i’m supposed to clean the area surrounding the liners thoroughly.
And then it is up to me whether to pull the liners or draw the pistons ? In fact i have not opened the oil sump yet as i will receive my engine lifter only these days and the engine sits in the garden since it was delivered last week.
And of course I will mark all pieces and photodocument each step (not to come to a point of no return :wink: ). I have seen that there eist tools to clamp the liners down but that DIY holders will also do the job.
I saw a set of rings being purchased at about 300$ whereas a complete Mahle set including pistons, liners and rings is about 1200$. From that point of view it seems more reasonable to change all or are the rings too expensive there ?
I can not feel any bore wear with my fingertips or -nail - can i measure these tiny 0.001 somehow by myself (e.g:renting an instrument ?).
You mention that a head skim is highly recommended. I did not even depart the camshaft yet (lacking the 7/32" hexa) and was almost thinking of leaving it alone and put it back on.
Is this also true for the block (to have it skimmed) - as i then would have to exchange all studs (I planned to keep them or only exchange the mid 10 ones). Of course renewing every single part will be safer but this engine is only my playground and “only” an XJ engine.
Would I be able to install liners and seal them at the ground with Loctite with at my DIY site ? How is the proper vertical position guaranteed and how many 0.001 can the head gasket compensate ? Sorry for that stupid questions but my only engine disassembled was a moped’s :smiley: I would almost feel safer/more confident in leaving the liners in and removing the pistons downwards, clean them and reinsert them with new rings. stupid ?

Thank you so much for your help !

Kirby Palm:
“Turn the crank until the piston in the one unrestrained cylinder is at the bottom of its stroke, and then continue turning the crank while encouraging the liner to come up with the piston. When the piston is at TDC but still at the bottom of the liner, the ledge on the side of the liner that sits on the block will be higher than the head surface. You can then carefully clean the surface on the liner and the block, apply new sealant, and slide the liner back into place.”
sounds so easy :stuck_out_tongue:

Hi Tom you can’t get pistons out from the bottom! When you have the sump off, look inside to see if you can see any brown watery stains on the inside of the crankcase. If so,this points to slight water leaks past liners. If so, you should remove them, throughly clean everything and reinstall with a glycol resistant sealant. loctite do one which is grey in colour.only s thin coat and clamp down the liners immediately to ensure they are at the correct height once the sealant cures.

No need to skim block face - normally a good degrease and light emery will do.
If studs are not really badly corroded, don’t attempt to remove them! You could get into a world of trouble as they can be VERY tight and do shear off readily.
Is your engine a 5.3 litre? If so that sounds a high price for a set of rings!
You could try XRN in Godalming UK?
Much cheaper than that!
If pistons aren’t scored and neither a liners so be ok to use again.
Get pistons vapour blasted. Ideally it’s best to put a glaze buster down the liners with light oil coating.
You would be better doing this with liners out but if not, you can do it if they’re in the block if the crank is out, or cover to crank with rag whilst you do it and throughly clean everything afterwards.
Remember the inside of any engine should be scrupulously clean before assembly- just add clean oil!
Best regards
Nigel Boycott

Hi Nigel, Thank you for all the valuable information.
Oh i thaught with the crankshaft removed all those pistons and rods could make their way out.
I had no compression on A2 and if i’m not 180° wrong it has to be due to the rings. So if i want to change the rings on this (better all ?) piston i do have to pull the liner/s or at least that would be the way to do it. I have already contacted XRN awaiting their offer. Is that loctite sealant the same (blue or grey) that shall/can be used for the camshaft (574 silicone sealant) ? So as far as i understood at the bottom of the block there will be an exact seat and the length of the liners are precisely matched to touch the head gasket. - edit: removed error regarding piston direction

I hope i find someone doing vapour blasting - would dry ice blasting also do the job ?

The studs don’t look too bad i think and i will clean them and then leave them alone. I heard of stud drilling - must be a horrible job down there …

So i will secure the liners, do some cleaning and when my engine lift has arrived i will have a look at the crank and cry for help :wink:

Regards, Tom

My 2 cents…I’ve found that low compression can be due to bad rings and/or a valve problem, but ZERO compression is “usually” a valve leak…just my experience. Easy enough to check valve seal with alcohol and compressed air from back side of valve(s).

Hi Lee !
Thx for sharing your experience. How is that being done and can it really be that this valve leak is not visible in any way ?
(I guess see where the alcohol vaporizes first ?)
Do you think i can also pressure check the piston. i have some spare 8mm iron plate wide enough to cover the liner and could drill some holes for the studs and a center hole to check the pressure ?

Hi Tom
Loctite 574 is ok. You just need to clamp the liners down onto the sealant BEFORE it cures or it could then hold the liners off the seating
face. Then the head gasket would not
form a good seal.
If you had no compression on 2A you need to check both the piston and rings carefully for wear. Also don’t forget lack of compression could be badly seated valves?
Best regards
Nigel Boycott

Lay the head flat, then just pour some alky into the chambers(s)…the intake and/or exhaust ports will drip alky if you have a bad valve-to-seat-sealing situation. OR, you can simply apply compressed air to the backside of the valve and look for bubbles coming up thru the liquid. I use alky cos it dries pretty clean as opposed to some kind of light oil…just less mess.

Oh i see, so i will use Isopropyl alcohol tomorrow and check.
It was my interpretation that if the valve springs are good and the valves are not burnt the zero compression must relate to something different. (On the other hand i did want to remove the heads because i was curious :wink: )
Thx !

Hi Lee,
I have poured plenty of “washing gasoline” in the chambers and all valves and their seats remained dry. Even after i “pushed” the fluid with my compressor nothing changed. The heads were a little “cleaned” with compressor before . The left one is A2 btw.
Can it be that the piston rings are corroded and not even brken because of long standing. I don’t know the history of this engine but for me the dirt one the head and the combustion chamber looks just as the other cylinders so i doubt that this failed for a longer time. how does a spark plug or valves look like if the engine runs “without” piston rings ?

edit: when i had a look how effective this gasoline was in cleaning it appeared that the exhaust valve in A2 “misbehaved” :slight_smile:. So i guess i did something wrong in my test before …
picture about 30 seconds after fluid had been applied.

If both valves are in the closed position, see if you can get a thin feeler gauge,with a fairly pointed end, between the valves and the seats. This will tell you if the valves are not seating properly. Does sound like a piston ring problem though, from the appearance of your cylinder head in the photo.

Hi helpers !
I have now drawn the valve and it looks as if this was the source for 0 compression:

I purchased a can of Teroson VR2200 and a handtool ready to polish the valve and it’s seat.
Is this the right way to go or should I get any new parts. Again the shaft of this valve does not seem to have any burrs at all (for a rookie at least). If I have done this procedure with this exhaust vale should i do all 23 others also or is it a waste of time ? What else is advisable at this level of disassembly. i.e: both heads off but and oil sump still in place.
Is there any measurement to be done before the head is reassembled with new gaskets ? I know most of you will advise me to have the heads honed but will this really be necessary if there was no major problem with the engine and the heads came of easily with my plate. Also i saw people cross honing there liners - is this also done for this engine as my liners have no cross hones at all.
I’m preparing a list of gaskets and stuff to be ordered at sng - xrm does not deal with individuals. when looking for seal rings i encountered the brand “total-seal” offering a double ring. I was thinking to use those in my XKE engine (the matching number one). What do you think about this ?

Thx for all your help !!

… Having a beer now after my FIRST timing chain, head, camshaft and valve finally :wink:

@nigel: do you think i should have a look at the liners in any case ? what indicates possible/likely problems with the rings ?

edit:the tappet shim is 0.100" - is it likely to require thinner ones and what is the “typical grind difference” if so.

Ideally you should check the liners for wear with a "rock- it "type bore gauge,but see if there’s any evidence of a lip at the top of the liners, check the pistons and liners for any sign of scuffing or , worse still grooves.
If not heavily marked or worn liners or pistons lightly deglaze the liners and fit new rings. Pistons should be really clean and put back into the same liner, the same way round - this is easy to overlook!the liners are not offset, so they will refit either way round Mark the front BEFORE you remove from the block obviously mark them A or B 1to 6

I would seriously consider getting the head faces skimmed. When you’ve stripped them this far it would be foolish to not do it!
Tappet shim range is measured by the alphabet. “A” thinnest and “Z” thickest.
“P” is 0.100" they are graded in 1 thou increments.
Valve guide and stem wear should be checked. I know it’s a pain, but you should at least grind in all the valves! If they’re in good condition shouldn’t take too long (ish!)

Looks like a bent valve…needs replacement.

Hi Lee,
Yes i tried to grind it but “nothing” remains and I will definitely need an exchange.
As Nigel advised me to have a look at all 24 valves and exchange the piston rings too, should i replace all valves or just the suspect one/s ?
Has anyone infos about “total seal” rings - if new then the best no ?
I want to dry-ice clean the whole engine outside and inside, carbs, manifolds maybe also bottom area. Is this a good idea and what should i take care about especially ? I think it was best to do this with the liners still in place and secured ?

Did you chuck-up that valve into a drill motor to verify it is bent? Assuming it is, the cause needs to be investigated…valve float due to bad/broken/weak valve springs means new springs…don’t know if you can by less than a full set, though. Don’t know much about the V-12 cylinder liner design, but since this seems to be a “spare” engine, I would be very reluctant to break down the engine too far since reasonably smooth bores and new rings should yield acceptable results, especially considering it looks like the bent valve was the cause of the zero compression you measured.
SO, I would lap the valves, replace any that need it, install new springs, piston rings, bearings, gaskets etc, but pretty much leave the cylinders and crank alone. JMO.

Thx Lee,
Well i grinded the valve so now it has become “shiny” on half of it’s radius and it sits already quite deep in the seat.

But when ran in the drilling machine it does not appear to be bent.
So I will order new springs for both engines and a set of valves for the XKE and only those needed for the XJ engine.
And i could buy a set of pistons, liners and rings use the rings for the XJ and total seal rings (if affordable) for the XKE.
For the XKE engine (which is completely disassembled and i haven’t seen it for long) I’m not sure if a dare to reassemble it by myself or better a shop does the job. I will see when i see it :wink:
The chain seems quite good but as it is cheap should i replace it and would i be able to find the correct timing again without that special tool (e.g. counting teeth) ? I did not even dare to take off the timing cover yet :stuck_out_tongue:
Yes your list was about my expectations (i.e: ~ 500 to 700€ in parts). Which bearings ?
And CO2 blasting is a good idea - it would be hard to clean the water area around the liners otherwise ?
Thank You !

Aren’t the rods out?..rod bearings. And chains are cheap so probably worth it. I’d check to see if another ex. valve would seal in that seat…either the original valve or the seat is toast.

No i did not yet draw the liners and will take off the oil sump tomorrow.
Big End Bearing Set you mean ? +0 +10 or +20 how can i find out ?
And also main bearings ?
I was thinking I could leave “that stuff down there” - draw the liners and push back with new rings in place ?