Do it in a day: Repair broken manifold stud



The O series engine consists of iron block and aluminium cylinder head. The original manifold studs that are threaded into the head can snap off leaving very little of the stud to work with and more often than not mean the head would have to be removed and sent to an engineering company for repair.

Here we will show you a way of making this repair yourself with the engine in situ.

Firstly, you will need the following tools and parts:


5/16” UNF blind tap (to clean out remaining holes on head).

5/16” UNF thread repair kit (includes: HSS second tap. HSS drill bit, coil driver, tang remover and inserts)

Tap driver

Battery operated drill (variable speed with various drill bits)

Drill punch

Die grinder with a 40grit flapper wheel (or grinder with a 40grit flapper wheel)


Calliper gauge


Our engine is in the process of being fitted back together so we have a lot of space around the N/S of the engine. You may need to remove the carburettor, air box and manifold to gain access here. We were also lucky that the stud that snapped was at the front of the engine.
Start by cleaning out the remainder of the cylinder head stud holes with the 5/16” blind tap and measure their depths with a calliper gauge.


Next, you will need to use the flapper wheel to carefully grind down the stud so that it is flush with the face of the head. Get the stud small enough so that it protrudes slightly and use a file to flatten it down so not to damage the head.


Now take your drill punch and mark the centre of the old stud Make sure the stud is flat when you punch it in the middle


Carefully start drilling the stud with a 6mm HSS bit slowly. Check your alignment of the drill to the stud. The idea here is to eat into the old stud and remove it. You must continually check the depth and alignment of the hole as you do not want to go too far and drill into the oil gallery! Check depth against one of the other holes.


Move up a drill size once you have got the correct depth making sure you do not go above 5/16” at this point!
Clean out stud hole with a hoover


Once you are happy the stud is gone and the depth is correct, take the over-sized HSS drill bit from the repair kit. Centre your drill across the stud hole and drill out the hole.


Take the HSS second tap from the repair kit, centre it over the stud hole and carefully tap out the hole. You may want to use a light oil here to help lubricate the tap during this process. Wind the tap in and out a couple of times making sure that you have gone down all of the hole and removed all of the swarf. You may want to hoover out the hole before the next step.


Using the coil driver from the kit, carefully wind in the insert into the stud hole. Once you are happy that it is flush with the cylinder head manifold face take the tang removal tool and tap the end off the insert. The tang tool is magnetic and will hold onto the tang when it is extracted.


Test fit a new stud, or bolt.


You can now re-fit the manifold.



Do it in a day


So you have a daily driver that needs attention, or a project that needs work but you don’t have a lot of time to get really stuck into it? Why not figure out what jobs you could do in one day.

In an up and coming series we will guide you through some of the jobs that don’t have to take an age to complete, if you plan and prepare the parts and tools in advance.

Not only will we be covering general mechanical jobs, but a bit of welding and bodywork too. We will also go through some more basic tasks for owners that are new to the Marina or new to cars in general.

So stick around and take note of Do it in a day.


Coming up in this series:

Repair broken manifold stud – Live now!

Valve grinding and stem seals

Jacking point repair

Floor pan replacement

If you have any jobs that you want covering, please let us know and we will do our best to fit them in.

Do it in a day: Floor / Jacking point repair


So you have a daily driver that needs attention, or a project that needs work but you don’t have a lot of time to get really stuck into it? Why not figure out what jobs you could do in one day. Apart from the normal maintenance jobs like: Oil service, suspension greasing and brake adjustment, what could you do in a day?

My LHD some of you know. This car was imported back in February and transported back to the UK by my friend Martin Wallis. Since being in my workshop very little has happened to it, apart from being put on axle stands – I’ve even had it for sale both in the Club’s magazine and website but it hasn't sold. No one seems to want projects.

The car is extremely solid and only needs a couple of little bits of body repair to make the shell 100%. My task for today is to cut out and repair where someone in the past has used the car’s jacking point and it has lifted up through the floor a little. This is a common area that needs attention in most old 70s BL cars, especially Marinas. With this car I have been lucky that the rest of the floor area is spotless and it only needs a small patch letting in.

Tools for the job (these are what I used – you can substitute to suit).

Socket set (removal of front seat)
Screw drivers (removal of trim)
Welders blanket (if leaving some interior in place
Block of wood
Body hammer
Sharpie pen
Tin snips
Cardboard (corrugated)
Cut off wheel (or grinder with a 1mm cutting disc)
Flapper disc (40 grit)
Masking tape
Sandpaper (coarse grit) or Die grinder with attachment wheel
Drill (with wire brush attachment)
Spot weld drill bit
Various drill bits
Workbench and steel for forming
16 or 18 guage steel plate
Weld-thru primer
Zinc rich primer
Body matched paint
Cavity wax
Seam sealer


  1. Remove front seat, carpet retaining strip and carpet


2. Remove underfelt and protect trim with welder’s blanket


3. Inspect affected area – use block of wood and hammer to knock jacking point back (make sure to check integrity of jacking point first).


4. Clean area around jacking point with sandpaper and mark sport welds.


5. Mark area to be repaired with masking tape.


6. If the jacking point is to be replaced, carefully drill out spot welds – be sure not to go through both levels!


7. Using a cut off wheel (or angle grinder with 1mm cutting disc) carefully cut along your marked lines. We will be attempting a butt weld repair here as it will be neater, if you are replacing the complete jacking point you can do a lap joint and seam weld or plug weld the panel into the floor.


My repair will be in two pieces as I want to try and retain the original look from under the car – I am also plug welding this plate onto the original jacking point.

8. Clean up both sides of the floor and be sure to clean out the original jacking point with a wire brush attachment if you are keeping it.



 9. Make a template from corrugated cardboard: A simple way here is to cut a piece of cardboard about the same size as the area to be repaired – press it against the edges of metal – turn it over and you will have a base to start your template!

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10. Cut and trim cardboard to suit – if butt welding, make sure you leave a small gap all the way around (roughly about 1 – 1.5mm).


11. Paint all areas with weld-thru primer (once in bare metal).


12. Transfer cardboard templates into metal using tin snips – trim to suit as necessary.

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13. Here I have drilled the top piece of my repair so that I can plug weld it to the bottom piece. I have also re-plug welded the original spot welds after I removed some rust from them.

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14. Once you are happy with the fitment of the patch spot weld it into the floor making sure not to overheat the repair. You should alternate your welds across the patch until they look like a continuous seam weld.

15. Clean up the welds as you see fit.


16. Prim bare metal with a good quality rust inhibitor primer.


17. Use seam sealer to protect welds.









18. Prim area on both sides with a zinc rich primer









19. Paint to match body colour

20. Wax cavities with a quality wax