(Disclaimer - the following explains how I replaced the manifolds on my car. This is purely advisory, and is given in good faith. This method may work for you, and it may not. If it goes wrong, then don't blame me!)
Changing the exhaust manifolds sounds simple - each side involves 6 bolts or studs holding the manifold onto the cylinder head, and 3 bolts holding the downpipe (or the catalyser or cat replacement pipes on S3C and S4C models) on. You also have to change over a lambda sensor on cat-equipped models.
Those 6 bolts or studs are the problem - I have been told that there is virtually no chance of getting them all out without one snapping - when that happens it's time to take the engine to bits to get the heads off so you can drill the broken bits out: there is no chance of doing it in place on the car, space is just too tight. Not the preferred option!
A week or two before you propose to start, give the 6 bolts on each side a good soaking with a good penetrating fluid. Use a proper penetrating fluid, not just a thin oil - you need to make sure that it creeps into the threads and breaks any rust holding the bolts on. In my case, I gave them a soaking a week before I started anything else, and then another soaking and a thump with a hammer (not too hard - just enough to shock any rust bond) just before I started.
Check that the parts look right
The first thing to do is to take a really close look at the new bits you have ordered, to make sure that they are the
same as the bits you are taking off. In my case, the manifolds look fine. This photo shows the
new one sitting above the old rusty one. Happy with them.
I notice that the two downpipes are a different shape and length. Now having spent considerable amounts
of time re-attaching these pipes to the car after scraping over speed bumps etc, I know that they should be
the same length.
One of them would fit - it's the same as the left-hand one on the car. The other is a completely different shape and length, and looks like it would either foul the chassis, or not reach far enough back. As it turns out, I was wrong: the short one fits fine and the longer one had to be shortened.
The supplier says that the exhausts are made from an original TVR exhaust pattern. This is always a problem with mixing bits from different makers - will supplier A's downpipes fir the rest of supplier B's system (especially when you don't know who supplier B is because the system was on the car when you bought it).
This shows the existing downpipes, the discoloured steel pipes up the middle of the car. It also shows that the
chassis paint needs some serious retouching!
This photo shows how the existing pipes have almost been squashed
flat by various impacts with the ground, on rough roads and speed bumps. That was when the front of the car was
lower than it is now (since I put the new springs and shocks on, last year).
You'll see that the exhaust clamps are directly under the sump, with a risk of the bolt
being pushed through if it grounds. The new downpipes are shorter so that the clamps end up in front of the sump,
in the space behind that red chassis crossmember. (Yes, the existing joint does overlap by that amount!)
Start the Job
I jacked the car up, making sure it was well supported on axle stands or similar. There's no need to take the wheels off - you only need enough height to be able to get underneath.
Right - to give myself enough room to work, I take off the fan belt and alternator, the air filter and hoses, then the real fun begins... removing the exhaust downpipes. First I remove the decat pipes. 3 bolts hold each pipe to the manifold, and another three to the downpipe. Non-cat models would only have the one joint.
Manifold Removal
Right, on to the dreaded tricky bit - the removal of the exhaust manifolds. First, if appropriate, remove the lambda sensors from the existing manifold - unplug the wiring connector and then remove with a 21 mm spanner. Warning - you won't get a ring spanner on because the wiring connector won't fit through the ring - you can buy a special socket with a wire slot up one side, but I used a good quality open-end spanner - good quality essential because they are bloody tight! Make sure you remember which is the left bank and which is the right - I don't know if it makes any difference but it's as well to put them back where they were, just in case.
Then it's on to the six head bolts. Take your time, treat each bolt as if it was made of butter and don't be in too much of a hurry - in this case, more haste could seriously mean a lot less speed, and for a very long time till you get the engine back together again. Don't get the socket set out and the biggest breaker bar you can find - I decided to use a fairly small standard 13mm combination spanner so that I don't get carried away by horsing on too much torque. Again, quality spanners are very important - cheap ones will round off the bolt head, or snap or something, before they turn the bolt.
I have a full set of Facom combi-spanners that I picked up years ago - they are absolutely superb. Cheap spanners
are a waste of money (I have cheap spanners too, but know that they are not for serious stuff like this). Although the
open end of this spanner looks broken, it isn't - they are designed that way and grip on the flats (ie bloody well!).
They also spin backwards without gripping, so they almost act like a kind of ratchet.
Make sure the spanner is fitted properly, and try to ease the bolt round. Don't hammer the spanner or jerk it - that increases the chances of snapping the bolt in the head. Just concentrate on one bolt at a time, and ease it out. Access to some of the bolts (especially the bottom ones) is extremely limited, so you'll only get a fraction of a turn with each spanner movement. Also remember that, in general, it's better to pull a spanner towards you than push it away - there is less risk of applying too much torque (because you're relying on strength rather than weight!) and you have more "feel" when pulling. There is also less risk of scraping half of the skin off your knuckles - although you should be prepared to see blood flow - if you are a hand model for oil of ulay or something, this is probably not the job for you - you WILL take a chunk out of yourself.
In my case, the offside manifold comes off surprisingly easily - the bolts come out one after the other.
This is the old and new offside manifolds. So far so good!
The nearside manifold puts up more of a fight. It's falling to bits anyway - it had been welded, brazed, filled, gun-gummed, fire-sealed and it was still blowing from ever-increasing cracks.
Four of the bolts came out fairly easily - the three top ones are easy to get to, and the middle bottom one comes off ok. The front bolt is already slightly rounded before I start, so the spanner doesn't grip very well, and I can't get enough torque on to turn it. The bottom back bolt is under the bulkhead and the spanner twists off before I can turn the bolt - only slightly rounded but, again, enough to prevent me turning it. I can't get a socket on because of the angle of the manifold pipes, and I can't use the old trick of battering a smaller socket on, because there's no room to swing a battering implement (ie a ham mer).
I need to get the manifold pipes out of the way to increase my options to get these bolts out.
I don't want to angle grind the pipes off because I'll end up with sparks of metal flying into the engine, so I start
to cut through the pipes with a hammer and cold chisel. Which takes bleeding ages. Again, it's a matter of taking your
time and being careful not to damage anything else.
This leaves the stuck bolts a bit more accessible (but still not visible!). I still can't get a smaller socket on, what I need is a socket that
drives off the bolt flats rather than the corners, but I don't have any.
You'll see in this photo that one of the top bolts is still in: I put 2 of the top bolts back in while I was chiselling,
so that I didn't risk breaking the 2 stuck bolts during all that hammering and twisting.
A visit to the shops - they don't have flat drive sockets either. What they do have is these Irwin bolt grips. They are like
sockets but with spiral
cutting flutes that dig onto the bolt head. Bloody hell, they're good! Stick it on, the bolts comes out no bother. The
hardest bit is getting the removed bolt out out of the grip - it's hanging on like a bulldog in a postman's leg. I need
big pliers and a hammer to make it let go (works on bulldogs too - pliers on the bollocks to make it scream and let go,
and a thump on the head with the hammer before it gets a hold of yours).
Anyway, the old manifolds are now off! AND no bolts broken, no engine dismantling required. Success!
Fit New Manifolds
Fitting the new manifolds is, as they say in the manuals, the reverse of removal, except without the huge variety of hammers, chisels, sprays, and no risk of breaking bolts.
In my case, I used new stainless steel bolts, washers and spring washers, with a good dollop of copaslip on each bolt thread before fitting. There is a bit of a debate about this - one school of thought is that stainless bolts lead to a galvanic corrosion reaction inside the head, and mild steel bolts are best. Another school is that mild steel bolts will only corrode again anyway so the stainless option is best. I opted for the stainless route because they look better, for longer.
Use new exhaust gaskets. Reusing the old gasket might work but it's a false economy - if it doesn't seal then you have a lot of work to do again to fix it. The gaskets come in two basic types - you can buy the three ports stamped into a single gasket, or three individual gaskets for each side, ie one for each port. I had problems before with a 3-port gasket on a Granada, where the distance between ports wasn't quite right and I had to put a slight fold in each gasket to get them to line up. I noticed that the gaskets on the car were also like that. So this time I bought individual gaskets thinking it would be easier.
Getting the new bolts in is fiddly (especially bottom ones), and takes a while because working space is so tight, and you end up trying to start the thread with the very tips of your fingers on the bolt head - unless you have reversible wrists you can't get your hands at the right angle to grip the bolts between finger and thumb. The 3 individual gaskets didn't help - they kept falling out and had to be lined up for each bolt.
Be very careful that none of the bolts are cross-threaded. Tighten them up with the same wee spanner that you used to get the old ones out, to make sure that you can feel that they are in the right threads. If they need any amount of force, they are probably cross-threaded - do not just horse them on - they WILL jam and they WILL break!
Then reconnect the downpipe joint - again I used new stainless nuts, bolts and washers. Put a spring washer under the nut - the joints do vibrate in use, and the when I replaced the cat pipes I didn't have any spring washers and had to replace two nuts and bolts which disppeared in use.
Then replace the lambda sensors, if appropriate, and plug them back into the loom.
All that remains now is to replace the alternator and fanbelt, and the airfilter and air hoses, and the job's done!
