Jaguar Classics (1946 - 1975) - 1969 4.2 E-type head bolts snapped - helicoil  
1969 4.2 E-type head bolts snapped - helicoil - MVP
Last summer, one of the bolts holding the head to the block snapped due to corrosion.

My mechanic has now got the head off, but two more bolts snapped in the process.

The bolts have broken near the bottom of the block, and need drilling/helicoiling out.

Does anyone know of a mobile service that could do this work in the Surrey/Middlesex border area?

Thanks in advance

MVP

Edited by Dynamic Dave on 13/06/2008 at 12:49

Tags: technical issues maintenance and servicing head gasket legal advice repairs

1969 4.2 E-type head bolts snapped - helicoil - yorkiebar
Wouldnt think you have got much chance of a mobile business doing this (in any area of the country).

It needs doing right, so the engine may as well be out and on a bench properly!

imo anyway.
1969 4.2 E-type head bolts snapped - helicoil - Number_Cruncher
I'm not sure yb - there are quite a few businesses who will go on site to repair and helicoil large, immovable machinery.

If the studs are still in place, how do you know you'll need a helicoil?, or has the mechanic already tried, and failed to drill them out?

If the failed studs are nearer the front of the engine, I can imagine access on an e type will be as good as it gets in-situ, and if a drill with a magnetic hold down base is used, the hole stands a good chance of being straight and true to the block.

Even without such a fancy drill, a decently thick block of aluminum with four machine drilled holes will make a very good drilling jig for a one-off job, and could be made using the head gasket as a pattern.

I would suggest that instead of looking at just engine reconditioners the OP widens their search to include more industrial maintenance concerns.

1969 4.2 E-type head bolts snapped - helicoil - topbloke
i know it won't help you much but we have quite a few around our area that drill out and helicoil etc so they are out there, may be worth calling an engineering firm or two and see who they recomend
1969 4.2 E-type head bolts snapped - helicoil - defender
number cruncher is spot on ,unless a failed effort to drill has already taken place a mag drill making a small hole down centre of stud then getting bigger untill nearly at the thread, then tap the old thread back to the correct size ,sounds easy in writing
putting the head back on and putting a sleeve in where the broken stud is for a drilling guide also works to get a straight hole in the broken stud
I would avoid the use of a stud remover in the drilled stud as when it breaks in the hole it usually means tears

Edited by defender on 13/06/2008 at 21:50

1969 4.2 E-type head bolts snapped - helicoil - yorkiebar
I will modify my answer then regarding NC's comment.

i dont think you will get anybody doing this mobile in any part of the country, for a price anywhere near that of taking the engine out and presenting it to an engineering shop!

Cost of removal of engine and transport and re fitting engine will (I expect) be way cheaper than calling out a specialist company to do this on site !

Again, I may be wrong, but i strongly doubt it!

1969 4.2 E-type head bolts snapped - helicoil - Robin the Technician
I would have thought that a head bolt would be hardened to cope with the strees's of high torque etc. I don't think just drilling is possible - it may need heating first to reduce the hardening of the steel iirc.

1969 4.2 E-type head bolts snapped - helicoil - defender
Robin they are not that hard ,a good sharp tungsten drill bit will cope with them and a stepped bit would be even better
1969 4.2 E-type head bolts snapped - helicoil - Robin the Technician
Thanks for the clarification re head bolt hardness - I suppose its not that hard if its snapped!!

1969 4.2 E-type head bolts snapped - helicoil - Brit_in_Germany
Spark erosion is a useful technique if mechanical drilling is not appropriate.
1969 4.2 E-type head bolts snapped - helicoil - Hamsafar
I had a stripped hole on a BMW straight 6 diesel, someone came out and did it for about £100, they had to redrill, tap and insert a helicoil (made by Wurth). That's all he did all day, mostly for dealerships where young lads were stripping threads on nearly new cars, he had loads of cringeworthy stories about dealerships!
1969 4.2 E-type head bolts snapped - helicoil - MVP
Thanks to all those who have replied

I have managed to find a local guy who does mobile helicoiling - he is due to come and have a look this week, so fingers crossed!

MVP
1969 4.2 E-type head bolts snapped - helicoil - MVP
At long last, I found someone who would actually get off their backside and do the job !

Lots of timewasters, and companies who want the engine taken out and delivered to their workshops etc etc....

I called Sutton Rebore Services last Monday & spoke to a gent called Mike - he knew the problem and what to do. He came out on his motorbike today, and 45 minutes later , the job was done - BRILLIANT

I'll be driving my baby again soon :)

MVP
1969 4.2 E-type head bolts snapped - helicoil - Armitage Shanks {p}
Glad you got a result that didn't empty your wallet/piggy bank!
1969 4.2 E-type head bolts snapped - helicoil - Robin the Technician
Hi MPV,
Great news on the repair. Can you enlighten us on exactly what he did - 45 mins seems very quick.

1969 4.2 E-type head bolts snapped - helicoil - MVP
Robin

On taking the rest of the studs out, 2 more failed, i.e. a total of 3 of the long studs that go through to the bottom of the block had now snapped.

At the top of the block, in the holes where the studs go through, Mike cut a thread with a tap/die tool. In these new threads, the helicoil, which is just like a tight metal spring, is screwed into the thread. The thread inside of the helicoil is the size of the original stud thread.

The XJ block has short studs at the back and front that screw into the block (in the same way as the new helicoils). I will now buy 3 more of these short studs to go into the helicoils, which will end-up the same height as the originals.

The tools and parts required would fit into a large jacket pocket - why engineering companies wanted the engine-out at their premises to do the job is beyond me.

MVP
1969 4.2 E-type head bolts snapped - helicoil - ifithelps
All this talk of helicoils reminds me of the time I undid a wheel nut the wrong way.

Using an airgun on the nearside wheels of a Transit - never thought they would be a left hand thread.

Turned the gun up a bit more, nut started to turn, although it didn't 'feel' right.

Nut now spinning freely, but still in place.

The thread of the nut had stripped cleanly and I was able to slide the nut off the stud.

The thread was still on the stud.

I carefully unscrewed the stripped thread, which came off in one piece and looked just like a small spring.

And it left the stud undamaged, so all my hamfistedness cost was a new nut.

Must have been designed to fail in that way.
1969 4.2 E-type head bolts snapped - helicoil - Number_Cruncher
>>Must have been designed to fail in that way.

That's an odd case. Current design practice is to make sure that the shank of the fastener snaps first in an overload condition. However, it's entirely possible that the wheel studs/nuts were not designed using those rules.

1969 4.2 E-type head bolts snapped - helicoil - bathtub tom
>>the long studs that go through to the bottom of the block had now snapped.

Is there a reason why these studs are so long?

1969 4.2 E-type head bolts snapped - helicoil - Screwloose
Is there a reason why these studs are so long?


Clearly there... was?
1969 4.2 E-type head bolts snapped - helicoil - MVP
>>the long studs that go through to the bottom of the block had now snapped.
Is there a reason why these studs are so long?


As the front and backs are only short studs, i.e. long studs not needed to keep the head on tight, the only reason I can see is that these are to support the engines weight if it's being lifted out (there are two brackets using some of the middle studs)

A poor design IMO, as the studs run right through the coolant, and are bound to corrode in time.

The only interesting point was the three that failed were all on the same side (carb side); I couldn't see why this should be so.

MVP
1969 4.2 E-type head bolts snapped - helicoil - MVP
I got a call from my mechanic who has now got the engine running sweetly again.

It's bonnet on today, and off for an MOT tomorrow :)

MVP
1969 4.2 E-type head bolts snapped - helicoil - Armitage Shanks {p}
There's a nice early Christmas present for you!
1969 4.2 E-type head bolts snapped - helicoil - noodles
That?s a great question and it gets to the essence of this problem

The Jaguar XK 4.2 litre is a fabulous engine but like most good things it has its flaws.

It was the final development of the XK engine which started with a capacity of 3.4 litres in 1948. Jaguar bored this out to 3.8 litres and then 4.2 litres for the E type. These motors were also fitted to the Mark X and 420 models. The effect of boring out all that metal showed in the early 4.2 units which suffered from a lack of torsional rigidity so Jaguar redesigned the block for the XJ6 so that the head studs which had previously screwed into the top of the block were lengthened and taken down through the water jacket to bolt into the block at the base of the cylinders. The whole motor was much more rigid and this was an excellent fix. These motors were fitted to the 420G and I presume to the E type too.

When these engines age and especially if they are not looked after with the correct grade of coolant with sufficient anti-corrosion properties the long studs corrode just above the insertion point. The correct fix is to get access by knocking out the blanking plugs in the side of the motor to gain access to the stump of the stud then using an extra long drill and an extra long tap either with out without a helicoil to repair the damage deep in the block. This takes exceptional skill and I think can only be done with the block out. Most people look for a new block!

I have never heard of putting a helicoil into the top of the block like this. It?s an ingenious solution but unlike the older XK motors, the top of the block in the 4.2 long stud engine was not designed to take the load from the head studs. Obviously one doesn?t wish to make the repair unnecessarily complicated but with 3 of the 10 long studs repaired in this way it does raise some concerns about the motor?s condition.
sq

Edited by Pugugly on 21/06/2009 at 10:23

1969 4.2 E-type head bolts snapped - helicoil - none
Interesting reply from Noodles. I can remember talking to a Jaguar mechanic back in the '70s and his view was that the strongest engine was the 3.4. I can recall him saying that the larger engines were 'overbored' and weakened.
1969 4.2 E-type head bolts snapped - helicoil - MVP
Most of the bolts are short and are tapped into the top of the block only.

I think the long bolts were there to aid the lifting out of the engine, as there were lifting "loops" on the top of these.

Anyway, the engine is running beautifully with no ill-effects :)

MVP
1969 4.2 E-type head bolts snapped - helicoil - noodles
I found this article on "jag lovers forum" (!) might add some more to the debate relates to XJ series 3 but i think the block is the same

Michael Neal?s Technical Advice : File 1
Head Stud Breakage

If a stud does break there are a couple options. I've had to repair a number of cars that the local under educated butchers have mauled. The most common incident is to repair a broken stud by tapping the top of the block. Many times the head has been drilled to 1/2" also to put a bolt in. Many times the repair was attempted with the head still on the car. Needless to say, they all leaked. If a stud does break there are several avenues. If you are feeling cheap and pressed for time don't even think about threading the top of the block. Most S3 blocks have a narrow passage between the cylinders that intersect with the stud holes in the deck surface. When the hole in the deck is threaded all it does is spread and will not hold torque. A quick fix is to use a thread-sert, a machined heli-coil basically with a shoulder. Remove the freeze plug for access and insert it upside down up through the stud hole in the deck. This provides a fairly good anchor. Use a short stud like the front or rears and it even looks oem. The correct way to repair a broken stud is to remove the freeze plug for access near the stud base. It may not have broken off flush so the stub may have to be removed. My weapon of choice is a 90 degree die grinder with a fresh carbide bit. With a bit of grinding you can remove the protrusion. Grind it down so you just start to hit block material. This will outline the stud. Use a new titanium coated drillbit welded onto an old stud. Start a pilot hole with a smaller bit first. Don't drill too far or too much off center. Too deep will end up in the crankcase. Of course this is much easier with the head off but I have done it with the head on. With a low speed, high torque drill you can make short work of this. Next, retap the hole. Finish it off with a bottoming tap. These taps will also have to be welded onto old studs preferably with an old cylinder head nut welded onto the top. If you screw up go the next size up. This, however, will require a sized stud to be made, roughly $100. Stud holes must be cleaned and chased with a tap. Vacula makes a air blower nozzle with a 16" extension on it to reach down into the stud holes. Be sure to use a rag on the top of the block to catch the high speed debris. Use a bottoming tap welded to a stud to chase the threads. OEM style studs don't corrode badly using coolant properly. Snap On makes a great stud installing tool that backs off easily once the stud is installed. Installed height is 5 1/2" from the deck for the short studs and 5 3/4" for the studs that mount the brackets. Being a professional Jaguar Certified Technician with a whole lot of experience at repairing these engineering nightmares I have confidence in these methods and tecniques. I worked for a Top Fuel Funny Car Drag Racing as a bottom end man. Basically this is just damage control and maintenance. The motor is torn down after every run! One run puts the stress of 100,000 miles of wear on the motor. It is almost unbelievable what occurs. Worst case scenario is splitting the block into several pieces. From my experience I've found that the average mechanic tends to really screw up Jags. If you have to resort to a mechanic please find someone qualified. Would you take a prostrate problem to a oby/gyn? It's too bad that they don't require licensing to work on particular makes of cars.

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