For a V12 head that appears in good shape - really good shape what are the chances of not requireing any machining and avoiding potential head gasket issues.

As you may have seen in another thread I need to pull my heads to get some machine work done, cost not insignificant, I've found a really good pair of heads for around the same money.

What are the chances of these heads being OK with no machine work - just a Scotch Brite and bolt on ... givces me a spare set of heads / cams etc - or do I just bite the bullet and send my heads out - consider that my heads aren't off yet, I have 3 stuck bolts and one fouled thread - I have no idea what condition the head mounting faces are in - I don't expect them to be bad as the engine is near new but my luck on this car so far is non existent.

What would you do ?

Is there anything specific I need to look for in a machine shop handling these heads ??

Finally - I think I know this answer but before I finally commit will the heads come off without pulling the engine - to avoid buying yet another engine crane ...

 

Dont rely on chance when ever possible, it's a poor way to go through life.

Get a "machinest's edge" for 25$ and check it. Place the edge across the head at various places and check for true using a feeler guage to look for gaps.
This may be useful. This procedure is in just about every service manual I've come across.

 

Wish this sucker was available in UK, these things are so expensive here - wonder if it is time to move to the US ....

I just ordered a 2 ton crane to replace my 1 ton. I've done that process before with the straight edge - I guess the dilemna is go get these heads or just bite the bullet and get my current heads sorted -

The heads can be removed without pulling the engine but I've decided to say screw it - in for a penny as they say - I can pull the asbestos and kill any rust underneath it - I've given up on driving the car this year now.

 

There is no simple answer to your question. If the cooling system has been correctly maintained and the engine never overheated, then there is a possibility no machine work is needed.

The main issues to look for with any aluminium cylinder head are warping, cracking and corrosion. To do the job correctly means removing the heads and having them checked for those possibilities. Pay special attention to the coolant passages as they can be corroded and require welding and machining to 'build up' the corroded areas. Corrosion near the valve seats may require extensive work to repair.

Since you now have the 2 tonne crane, remove the heads and inspect them.

 

Pretty sure my heads are fine in that regard - the engine is actually a factory reman unit that had very few miles < 6000 - I only need to replace / work on this thing because some threads are stripped and some bolts stuck,one bolt broken on the thermostat housing / coolant rails so I know my heads need a machine shops attention despite the low miles - I was replacing the stupid rubber seals on the coolant tubes since they have more in common with hard plastic than rubber seals - proven by one shattering on extraction.

I have the chance of a pair of good heads - the sure look it - so I'm weighing up getting those and just slapping them on then getting mine machined 'whenever' - so I get a pair of good spare heads - where my issue is lies with the 'secondhand' heads - I'm hoping to just throw these on, if they also need machine shop work then there is no benefit buying them.

 

Have the cylinder heads you're considering been refurbished and ready for installation?

Are the broken bolts proud of the surface, or did they break flush?

 

There are three bolts that wil break for sure, one kind of moves but either way if I get it out the thread is toast, one is broken off at approx 4 mm above the head surface, it is cold welded because it was moving yesterday (I just needed a decent 6 point socket to avoid borking the hex which came today) so nothing is removing that except a machine shop - even if I weld something onto the stub and get it out the thread is still toast.

The cylinder heads available are in pretty good condition based on the pictures I've seen - the place selling them makes V12 tables - I'm not debating my approval of killing good V12's for such a purpose ... since I need the heads ...

 

NOT my 1st choice at all.

You have NO proof that the heads have not been overheated, etc etc, probably anymore than the seller.

Dropped valve seats on overheated HE heads is kind of "normal".

Like you stated, some Scotchbrite and Elbow Grease can make anything look good as new for the sale process.

Many, many years ago we had a broken bolt on a BMW 740 V8. NO way was that engine coming out. I could not get at it good enough with my basic tools. So a look see in the Yellow Pages (you remember them??), and a "Mobile :Thread Repair" guy came in his WELL equipped van. He had all sorts of strange angle drills etc, 30 minutes, all done and Helicoiled.

I reckon they still be around, even in the UK.

 

Just to be clear - which is not your first coice - the unknown heads or getting the threads etc fixed in my own, I am leaning toward getting my own heads 'fixed' in a suitable machine shop (yet to be found) ... I just want this project ended - it is starting to drag on the patience and has gone way beyond the financially acceptable - it is getting out of control - I've spent stupid amounts of money so far ...

 

If it were my decision, I would go along with you and choose to have the heads on my engine repaired as I know their history. Either way, the engine needs to be repaired and the vehicle back on the road.

I completely understand about the amount of money being beyond acceptable.

 

Not my choice = the unknown.

There are specialists who could that in situ, unless you have a head gasket issue, leave that engine intact, That suggestions is based on your mentioning a Factory Unit with basically NO miles on it.

 

Another view:
If the engine has only 6000 miles on it, then it will be fine, as will the heads; the heads are VERY unlikely to be stuck at that mileage, so they will come off easily enough - this is FAR more of a problem on the V12 engine dis-assembly than any other aspect. Thus, pointless to buy another set of heads. If you do decide to remove the engine and get the bolt problem solved that way, the old heads go straight off and straight back on, no need for valve work, valve shimming etc etc, as the thing is effectively new.

Now, I am in general an advocate of the engine coming out if doing a full refurb; it allows such easy access to do things like gaskets, prpoer cleaning, ensuring the engine bay is rust free and thereafter - SO important - rustproofing everything and inside the chassis rails etc etc. BUT, Ben, you seem to be saying that the engine only has to come out because of the water manifold bolt problem and that the engine is effectively new. In this case, what is to be lost by getting a broken bolt removal and repair specialist to have a go? There again, if that voice inside is saying "remove the engine and do the proper job" that must be obeyed!

So if it were me, I would put a rattle gun on them and give it a whirl, grunt will not do it, shock loading might. And do NOT forget the two holding in the AAV, these are the same with the same problem.

 

Yeh the unknown sucks.

I've gone so far with this project that "pull it and do a proper job and be done" has overtaken the impatience to see it back on the road, so much so that I bit the bullet and broke down the AC and cleared the engine of all remaining connections - can't get the damn oil cooler unions undone - was a little perplexed by the wires from the distributor which go to a plug that was installed on the AC compressor, I knew they went to the front but didn't expect to find them hooked up to the AC compressor - surely not - thats a challenge for another day.

Although I've now finished the repairs on the inner wings (except for paint) I did remove the pedal box / brake servo and insulation and there is zero paint, no penetration but a lot of surface stuff which also extends behind the heat shielding, I'm so fed up of srtruggling and working upside down after repairing the inner wings that the engine is coming out, it eally isn't so much additional work. I'm never going to remember where everything goes so it's a good job I like puzzles.

Maybe an air hammer is the next tool to buy - I do have an impact gun which is more than capable of breaking these bolts but I've seen some interesting tricks performed with air hammers on YouTube.

My AAV is out, been out for a long time - had it rebuilt - thought this project was a simple refurb ala Grant's notes ....

I'll see if I can find somebody local that can provide the service you mention - removing bolts / rethreading in situ etc but I can't find anything obvious sat here with morning coffee - I'm sure their life will be easier with the engine out (can barely get a socket on one of the nightmare bolts (rearmost on bank A)).

Edit : There are no mobile extraction people anywhere near me it seems - if I lived in London I'd be laughing there are loads - but I'm 200 miles away - none of the London services are prepared to make the trip

 

Ben
There re loads of guys who do it. Google "broken stud removal services UK"
e.g. https://www.threaddoctorservicesltd.co.uk/
Not local to you, but they are out there.

Retapping the head is something anyone can do, no need for a machine shop once the old broken part is out.
Greg

 

Yes - found them - none of them want to venture out my way so far at a price I'm prepared to pay. The costs are such that it is cheaper to pull the heads and drive them to a machine shop - significantly cheaper given that one wants a 4 figure sum to make the trip and do the work

 

I've lost track of this thread (and your project) a bit, sorry.

This particular dilemma began as replacement of the seals for the coolant tubes, correct?

Do all of the water rail sections have problematic bolts?

If not, I'm wondering if those with problem bolts could be left alone and only the sections with good bolts removed. Then the tubes slid out of position and the seals replaced?

Throw the car on a trailer and take it to London.

Less work, and faster, than removing the engine.

Cheers
DD

 

What about the voice that says "I would like to actually drive this car someday"?

I'm not advocating crummy repairs but, sometimes, if you wanna get a car back on the road, an utterly uncompromising perspective becomes a roadblock. There might be alternatives that are not too hateful.

I have a pal who is very talented and very uncompromising. "If I can't do it right I won't do it at all" type of guy. That's admirable, but by his own admission the last hobby car he took on took fifteen years to complete. He has several others in the works. He won't live long enough to ever get them to the point of being roadworthy.

I've owned several Jags; my present V12 is my daily driver. I get to enjoy driving it every day. If I insisted on perfection every step of the way the car would never move out of the garage.

I 100% appreciate a job well done and I 100% appreciate "the journey" of fixing up and old car. But I've also seen projects die because the owner ran out of time, money, and patience. Shipwrights disease, and unwillingness to make any compromise or explore alternatives, got it the way.

I hope nobody here takes my remarks as being snarky. That's not my intent.

Cheers
DD

 

With YA Doug, 100%.

 

Apologies not necessary, I've not posted that much on the project to be honest I wasn't that sure anyone would be interested in my levels of stupid ... yes I was just replacing the rubber seals on the tube - I tested them by poking them before planning this and found them to be rock hard, I've since tried to remove one and it broke it is that hard so replacing these was for sure necessary.

That said only one section - front thermostat housing on bank B - came off without hassle, the rear piece on bank B has a broken bolt. The front thermostat housing on bank A has a bolt that started to gall it won't come out and won't go back in, the rear piece on bank A has two bolts that will break - I've busted so many over my years that I can tell by the feel of things that it won't end well if I persist but I will persist when the engine is out - but for now I need the lifting eyes on the engine to stay exactly where they are, I will lose the lifting rings if I break any more bolts - that said I'm surprised these rings on piddly little bolts are rated for the load but why else would they be there.

As for putting it on a trailer - fraid that isn't do-able either - there's no front subframe in the car the engine is sitting on axle stands, the car itself is sat on a pair of quicklift sill jacks. If the challenge of no front suspension isn't a big enough challenge if you add to the weight and size of an XJS, a trailer suitable for same, towing regulations here in the UK and having a vehicle suitable it just isn't cost viable. I could hire a recovery truck I suppose but that isn't cheap here either.

I think the biggest frustration is that the XJS is now totally in the way and holding up other projects - which is one more reason why I'm not happy.

This image shows the inner flitch below the brake servo - which is covered in rust (temporarily treated - it will be sanded back, re-treated and sprayed) but clearly the rust dives down behind the heat shields. I was going to put this as a future project - but it is now on the list and one reason I've decided the engine is coming out. Repairing the inner flitch panels was no joke - hanging upside down with a welding mask trying to weld what you can't see well with a welding gun at the wrong angle because of space issues ... combine that with arthritic hands and this wasn't any fun at all ...




Left Side turret - still need to open out the bolt hole for the coolant tank.


Right Side Turret - not as pretty as I would have liked - I struggled a lot with weld contamination on this side for some reason - waxoyl or something - not sure.

 

to add ,sometimes if an OHC head is resurfaced flat , the cam bores are out of alignment, so cams could run out and cause more damage!
but its a chance/guess to make!