As a novice to Stag engines, I thought I’d put down some rambling’s on how I went through changing the head gaskets. Most of the info is available in different posts, and obviously ‘old hat’ to quite a few of you. I thought it might be useful for those like me, who have neverattempted a big project like this before. Hopefully gives the ‘big picture' and various problems I came across.
I started the project being able to do most general servicing jobs, and having taken the heads off two previous 4 cylinder cars (Vauxhall Victor and Opel Manta)- a very long time ago!
Initial symptoms:
White smoke, running hot, lumpy tickover and finally spotted oil in the water.
Timescale:
I reckoned about a month or so. I've had plenty of time recently, so doing a bit each day should cover it. Actually took virtually 4 month’s, and not sure of how many man hours, but must be getting on for 100.
Scope:
Initially thought head skim, head gaskets, a few other gaskets, plugs, oil and that would be it. How wrong!
Prep:
I took a few pictures, and planned to bag and label all the nuts and bolts. In the end I didn't need the pictures but bagging and labelling items was well worthwhile given the timescale involved.
I got a CD version of the ROM off eBay and I printed off the engine part of it.
Special tools:
I got Tony Harts head stud extractor tool and then later, the water pump removal tool from Paddocks (just a ring welded to a bolt).
Getting to the heads:
The nuts on both exhaust downpipes were in poor condition. The carbs etc was fairly straightforward to get off. I labelled the throttle/choke cables. The bolts on the inlet manifold came out but were in poor condition. The inlet manifold wouldn’t shift so in the end I got a big ring spanner and the attached my socket extension through the ring spanner to get some leverage. I decided not to disturb the distributor.
Heads off:
Right hand head came off fairly easily using the extractor and first few studs on the left head. Remaining two - one sheared off and the other just wouldn't move no matter how tight I locked the extractor tool.
I looked up using the 'rope trick' and decided to try it. Nylon cord down the front cylinder until I couldn't get any more down and then gave it a fraction of a second on the starter. Oops, forgot to disconnect the fuel pump so fuel squirting everywhere! Got about a quarter of an inch up on the front. Pulled the cord out and put it down the rear bore. Again, up by a quarter of an inch. After this it’s a bit of a diminishing returns process as the cord is starting to move out of the bores. I’ve seen on the forum that sliding a piece of metal sheet between the head and the block will stop this. I didn’t have any to hand so didn’t try it. I thought, as it was the rear two studs causing the problem I would be able to lever the head up. After an hour it was up about half an inch. I tried a bottle jack wedged against the opposite head, but just bent the bottle jack base. At this point my neighbour came to my help with a crow bar. Between us – one pulling the other levering, we got it up enough to hacksaw through the sheared stud and used the extractor tool on the other. With the head off I could unscrew the sheared stud out of the block with my fingers.
The gaskets were just mush. Three had been leaking water into the cylinders – piston heads ‘washed’. Water had got through the gaskets and corroded into the heads in various places where there is not water passage. One of the water passages was also corroded close to the edge of the block. The water passages were semi-blocked by silt and debris – no wonder it ran a bit hot!
Valve removal was straight forward and I made sure each valve was pushed through a bit of card with it’s location marked. The valves had some pitting and a lot of carbons build up.
I had the heads skimmed, the inlet manifold threads re-helicoiled (most were a mess) and one of the passages welded at Green & Weatherly in Bushey. They also got the studs out of the exhaust downpipe.
Other jobs while the heads were off:
Water pump
I had no idea of the condition of the water pump so I decided to send it to Howard Vasey for overhaul. It didn’t come out so I had to get the removal tool. Even with the tool it took some pulling. Howard sends you back a re-furbished pump and gaskets within a few days.
Core plugs
Again, after a prompt from the forum (ta!)I changed all the core plugs. Although none seemed in imminent failure, there was some rusting. There’s only a slight difference in the size of some of the core plugs so make sure it’s the right one.
Temperature sensor
Saw that LD parts do a sensor that reads 90 deg at vertical. The one in the head was a bit scaled up so decided to change it.
Cleaning gasket surfaces
How many hours did I spend cleaning old gaskets off!? I guess it’s one of those tasks that it is worth spending a lot of time, on even though it’s a pain.
Clearing water passages
I spent quite a long time digging out the grunge that had built up in the water passages. I also took the drain plugs out and flushed thorough a few times with a hose. Must have been at least acup full of grunge and silt came out in total.
Hoses
I bought all new water hoses and replaced some of the fuel and breather pipes on the carbs.
Possibly should have done...
In hindsight, I probably should have changed the engine mounts. Looks like they may be tricky to get off with manifold etc in place. Maybe cleaned up the starter terminals too.
Re-building the heads:
My neighbour lent me valve spring compression tool and stand for the heads. Didn’t think I’d need the stand but it was brilliant. I ground in the valves the old fashioned way by hand. I was probably taking 30 – 40 mins per valve, so 8 hours just grinding in.
Taking quite a lot off the valves I spent a long time checking and re-checking the clearance gaps. In the end I changed every shim – again a very time consuming job with a couple of calls to Robsports for more shims.
I’d bought Payen extra thick gaskets as the heads had been skimmed before.
I cut down four of the old studs to 2 ½ inches and cut slots in the top to act as guides for the heads and to hold the gaskets in place.
Timing chain tensioners:
With the heads on and only loosly tightened down I couldn’t get the camshaft sprockets back on. As I’d cranked the engine over a few times, the tensioner’s had taken up some of the slack and there was no way the sprockets were going back on. Study the ROM, look at the engine…scratch my head. Have to re-set the tensioners.
Again from the forum suggestions I thought I’d get away with saving the sump gasket by breaking the seal between the timing chain cover and sump first. I took all the bolts off and then slowly worked a feeler gauge between the gasket and the timing chain cover. It’s awkward but possible.
The crank bolt was tight but came undone and I levered the pulley off using a socket as a base to lever from. Gingerly took the timing chain cover bolts out and pulled the cover off. It came away leaving the sump gasket intact! From the amount of congealed oil on the timing cover, the gaskets had been leaking.
The timing chain tensioners came out easily though the parts ‘pinged’ away when the spring released. With these off the camshaft sprocket went back onto the camshaft easily.
Referring to the manual the tensioners had to be held retracted by cut down washers. I tried this but couldn’t get it to work. As the tensioners locked down into the retracted position I fitted them and then found if you twisted them with a screwdriver slightly they would pop out and set the tension.
No problems getting the timing chain cover back on, although I did use sealant to position the gaskets in place. If I remember two have mounting lugs and one doesn’t.
Re-fitting the heads:
Straight forward using two of the cut down studs on each side to position correctly.
I fitted the inlet manifold to the heads before I tightened them down – big mistake. My thinking was that as I was using the thick Payen gaskets, everything would still line up. I torqued down the heads and tightened the inlet manifold, put everything back together and filled the rad. Water pouring out of both sides of the manifold. Searching the forum I found a piece on skimming the manifolds to get them to compensate for the head skimming. As the amount to come off seems to be trial and error I went for 10 thou of each side first. This still didn’t seem to work so I went for another 10 thou off each side. This plus boring out the bolt holes to 10mm and plenty of Wellseal seems to have worked – dribble free!
Other issues:
The ‘O’ rings in the carb float chambers had dried out and started leaking. Easy one to fix.
Getting the leads mixed up – how many times did I get this wrong!
Always wondered why it was difficult to start in the winter – found that one of the choke cable clips was broken allowing the cable to pull while nothing happened to the choke.
Non starter – Managed to borrow a spare coil and electronic ignition which worked in the end. Might just have been a dodgy connection.
New battery – managed to break a connector on the Kenlowe thermostat getting it out of the way.
Heater hose into heater leaked initially.
I’ve now done a couple of short runs and no leaks anywhere. Garage floor is completely dry – no oil or water. Not gone far enough to see how water/oil consumption is going. Nice even tickover and pulling well.
Ultimately a longer job than planned, a lot more side issues than thought and a mostly, enjoyable job....thanks to help from here
If anyone wants to borrow the stud removal tool, water pump removal bolt and cut down studs, pleasefeel free.
　
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