Roger King

Is the "expansion bottle" exactly that, or is it really a header tank with a screw-on pressure cap? Assuming the latter you would normally take the bottom hose from the header tank to the water pump connection and the one from the top of the tank to the thermostat housing. Note that the hose from the top of the header tank to the thermostat housing should be much smaller bore that the one from the bottom of the tank because it is only an air bleed. The usual caveat applies that I can't be 100% certain if I haven't seen the installation.

I'm afraid that there is no right answer to this. It all depends on how the builder of the engine set it up. However, there is an easy way to tell. Take the spark plugs out and turn the engine to TDC (there are marks on the crank pulley for this and you don't have to be dead accurate. Then turn the engine back half a turn and bring it back to TDC again, but this time with a finger over either number one or number four spark plug hole; one of the two will force air past your finger as it is on its compression stroke. Whichever one of the two does this is at its firing point when you reach TDC, so all you have to do is look at the rotor arm and wherever it is pointing will be the correct position for the cylinder with the compression, be it number one or number four. Your are correct about firing order and rotation.

Utterly useless and one of the great con tricks of the last few years from car manufacturers. I've been driving for forty years and have NEVER had a puncture that a can of splurge could have helped with. My wife bought a C-Max last year and we were given the usual spiel when I asked about the spare wheel - "not necessary", "this can will get you home", etc. I made my wife refuse to accept the car without agreement to supply a space saver when she signed the paperwork. She berated me on the way home for not believing the salesman until we passed an abandoned Mini with a shredded tyre (yes that honestly happened and it gave me a warm feeling of smug satisfaction of which I should have been ashamed, but wasn't). And then, on Christmas Eve a few days ago, I managed to rip the sidewall out of one of the rear tyres on a bizzarely placed kerbstone in a car park. No chance whatsoever of a can fixing that one, but I was able to fit the space saver and drive to a tyre supplier just before they closed for Christmas. This is all about cost cutting by manufacturers and the public goes along with it, seemingly in part because a lot of people now take pride in not knowing how to fix or maintain anything.

If you slam the throttle open on a car with mechanical throttle (be it carbs or injection), you will see a large spike of hydrocarbons popping out of the exhaust just a tad later (see SI units for definition of "tad"). If the throttle is opened just a little more gently this spike is greatly reduced. You also get a similar effect if you shut the throttle suddenly at high load. Fly by wire can stop all of this happening, although at the cost of the throttle feeling as though it is connected to the pedal via a rice pudding, an elastic band and a lump of warm blu-tak. There are many other scenarios where big brother control of the throttle will reduce naughty emissions. If you're used to such things it can be quite a shock to blip the throttle of a car equipped with well set up DCOE's - the response is instant.

It's other main use is to stop the engine from doing things that will make emissions worse. You may ask the throttle to do something, but it's not going to unless Big Brother feels you should be allowed to. It's a brilliant idea. I found this out when my wife's Tigra suffered a flat battery and on replacing it, the throttle would not work. We had to call out a specialist to reset the ECU so that it would recognise the relevant hardware. Can you imagine such a conversation twenty years ago? "Yes sir, you're battery has gone flat and this naturally means that your accelerator no longer works"

It's going to depend on your installation, but "probably" is the answer, although it would be easier if the inlet manifold was removed. Be aware that due to its being positioned in the worst possible place, a standard breather taken from there will pump out large amounts of oil, particularly on track. It really needs to be fed upwards and into the side of the rocker cover, with another breather then taken from the back of the rocker cover to a catch tank

I'm assuming that you do actually have a dizzy in the hole and are not running a wasted spark system. The oil cap breather is not enough breathing, even for a healthy engine. You MUST have a breather on the block, ideally one that feeds crankcase pressure up to the rocker cover externally and then exits to a catch tank from the rear of the rocker cover. If you don't have this, you are not only relying on a secondary outlet to vent the crankcas, but you are also forcing the crankcase gases up the pushrod holes which they are not designed to allow. Going back to the dizzy, there should be an 'O' ring around its shaft to seal it where it passes through the cylinder block; if this is missing or damaged that will not help.

This is usually "stand off". This is basically fuel/air mix bouncing out of the inlet tract due to the tuned length and will only occur at certain revs. The brown mess is fuel mixed with oil and muck from the filters. If you run an engine without air filters on the dyno you will often see this as a cloud of fuel vapour hovering around the inlet trumpets, but only at very specific revs. In your case it seems to be occuring at the same revs that you use on the motorway. If you are able, you might be able to reduce the effect by altering the total length of the inlet tract, but this is likely to have other side effects such as changing the shape of your torque curve or the need for different jetting which may or may not be an improvement.

Helicoil is most definitely not a poor repair. Indeed, we used to helicoil all important threads on the 420R Formula 2 engine from new, because when done properly they are stronger than a thread cut directly into aluminium.

I would welcome some information from the team about why Techtalk has been removed from public view. At present I can see no justification for it, but it is easy to take a stance that might have been different given more data. I don't remember any discussion or warning about the policy change before it was initiated.

I would welcome some information from the team about why Techtalk has been removed from public view. At present I can see no justification for it, but it is easy to take a stance that might have been different given more data. I don't remember any discussion or warning about the policy change before it was initiated.

Or, Why should I supply information F.O.C. to a club that then won't let people see it until they've paid?

I'm 100% in agreement with the above comments. I can see no logic in making TechTalk hidden. As many will know, I am no longer active in the club in the sense of having or working with Sevens, but I've always been happy to answer tech queries if I feel I can be of help. I've never had a problem with my replies being public and even preferred the "old, old" days when anyone, whether a member or not could post on Blatchat. Once it went "members only" for posting a great deal of potential help was lost. But this is now a step too far for me and I am considering whether or not to continue posting. I've not made my mind up yet so time will tell. Roger King

bearing size, bearing clearance, number of bearings and other items to be fed, metallurgy, etc

Generally, as Duncan says. But it does depend to a great extent on the bore finish and the type of rings. If you have a plateau honed bore finish and modern type rings you would normally expect to be able to drive fairly normally from the word go, but without giving it a total thrashing for around a thousand miles. If you have a non-plateau finish and old type rings, you need to be much more gentle initially. You do have to bed the camshaft in as well and general advice is to run at around 2500rpm for half an hour before driving the car. However, the ultimate instruction must come from the builder.

Actually, yes, now I see the top view it might make sense because you're curving round to match the angle of the inlet ports. It'll never be perfect because the ports themselves aren't, but there is some logic there.

Why the spacing? That doesn't conform to the spacing of X/F inlet ports and will therefore require curvature in the inlet tract which is not good for power.

You need to have the cylinder head helicoiled. This should be easy to do in situ without removing anything except the exhaust. Fitting oversize threads can create problems with clearances and you would also have to enlarge the hole in the exhaust flange. The thread you need is 5/16" UNC and this will take you back to the original specification. It would be worth running a tap down the existing thread to clean it up first, just in case you don't have a stripped thread after all.

I'm afraid that it may not sound terribly professional, but the only way to ensure a leak free join is to use plenty of silicone sealant on both sides of both the gasket and the rubber half moon seals. This is an area where modern engine design has improved tremendously; typically, you will have two flat machined surfaces to join, whereas a Crossflow has a crude pressing for the sump (of approximately the right shape) that has to seal round 180 degree seal carriers at each end as well as along the flat face of the cylinder block. Please be careful not to use too much silicone sealant though - it's not a good thing to have lumps of it floating around inside the engine.

Assuming things haven't changed since I built my last Crossflow - DO NOT go for the standard gasket. It is a cork/foil/cork sandwich that will not allow you to tighten the sump bolts enough to resist the vibrations found in a Caterham installation. Even slightly overtightening will just squish it out sideways until it is useless. The competition version is made of a composite material that will allow you to tighten things up properly without failing.

Almost certainly needs attention to either throttle cable stickiness and/or carb balance and idle mixture settings. You must also have a little slack in the throttle cable at idle. Unfortunately, a new spring is unlikely to deal with a sticky cable The only way to be 100% certain of the cable is to manually make sure that the carbs shut completely every time that you lift off the throttle. If they don't, disconnect cable from carbs and operate them by hand. If they now shut reliably, you need to deal with a sticky cable. If they are OK with the cable connected, you need to look at balance and idle mixture screw settings. It is very common for idle speed to be all over the place if the above are incorrect. Engine temperature can affect this quite dramatically. Typically, balance and mixture need to be set once a month for a road car, but this can vary dramatically from car to car.

This saga shows that you should NEVER connect the cold start device (it's not a choke, but an over-enrichment circuit). I've never known them give anything but trouble and they are completely superfluous. If the engine is healthy and correctly jetted, a few pumps on the throttle before cranking is all that you need to start.

If the engine is running OK on constant throttle, be it at idle or when driving, but won't pick up during transients (when you're opening the throttle), it sounds like the throttle pumps may not be working. Air has lower mass than fuel, which means that as you depress the throttle the extra air now admitted to the engine "gets going" more rapidly than the extra fuel that is sucked in through the carburettor. What this means in practice is that you go through a short period where the mixture is far too weak and the engine runs badly. Engines also like to be a little richer than normal during this period anyway, which just makes things worse. To compensate, carburettors have a throttle pump. This is really just a crude fuel injector that manually squirts a little extra fuel in as you open the throttle; the exact amount being determined by the size of the pump jet, the air bleed circuit and the stroke of the pump. In practice you can easily see if this is working by removing the air filters, shining a torch down the carburettor barrel and opening the throttle by hand (engine not running) as you look at the butterfly. If working, you will see a small trickle of fuel running down the butterfly each time you open the throttle a bit. You need to check all four barrels to make sure that all are working. If it is working, you need to look elsewhere. If not, you need to check the pump jets are not blocked and that the mechanism isn't seized. When you fire the engine from cold and give the throttle a few pumps you are actually squirting fuel in from the pump jets to provide a measure of cold start enrichment. Edited by - Roger King on 15 Aug 2014 17:46:30

Ditto the comment about the centrifugal (centripetal?) rotor arm. Twincams used to be fitted with them and they're a bit vague to say the least. What makes you think it's ignition though? A common reason for an engine feeling like it's hit an artificial rev limiter is a broken valve spring. Worth checking if you aren't certain.

Can't make any definitive comments here because I don't have enough info on the manufacturer of the parts, but............. In theory JIC fittings like this are to a common design standard, but in practice I have found that quality makes like Goodridge or Aeroquip are vastly superior in reliability. You can just attach one of the quality makes and know that it will not leak once tightened, whereas some of the cheap versions will not seal unless you waggle them during tightening to ensure that everything is nicely aligned. It's a classic case of getting what you pay for. Of course, the above assumes that the weep is coming from the joint itself and not some other source.