More updates, airbox thoughts

Work continues on the airbox and I've had a couple of quotes for aluminium cut to size for a backplate and sealing ring, £40 + VAT and delivery for the pair, so I doubt it's worth trying to make one myself or buying and cutting a ITG one.

So the plan at the moment is to have the aluminium backplate and ring supplied, that's the yellow and the blue parts in the cad image below, and then form the rest of the airbox from fibreglass or carbon fibre.

I'm not sure at this stage whether to bond the sealing ring into the airbox or just have it on top to spread the weight.

The best quote I had for the backplate was £30 plus delivery and VAT from LaserMaster, so I confirmed the drawing and paid them yesterday morning and this morning the parts were delivered.

Next job is to finish off the grommets, the ITG ones had a very large OD, meaning they would overlap, so instead I have managed to find some wiring grommets, though these need slight alteration to fit.

I was pleasantly surprised with the service after another company, who quoted £40+ also would only start work after the cheque cleared, LaserMaster took payment over the phone.

The first trial fit looks OK, I'm going to have to fettle one or two of the holes though to make it fit better (my measuring inaccuracies) and then add a mounting point or two back to the inlets to hold it steady.

Then I thought I'd make a start on the airbox, first step was to find something I could mould into the shape of the airbox to lay the fibreglass onto. First thought was to use that green flower arranging foam, oasis, but I couldn't find a large enough piece locally, so I got creative with a cardboard box, some plastic and a can of expanding foam to make this:

Which was roughed out to this, using a jack saw and rasp:

Before adding radii, covering in tape and trial fitting one of the air inlet pipes, which will be moulded in with the fibreglass:

Overdue updates

Right, so this blog has gone from being a bit out of date to being very out of date, so it's time to get things back on track.

Following my last missive, the inlet manifolds now all match-up with the head a lot better now after a bit of fettling and I've managed to get most of the butterflies to seat a lot better, one is still a lot worse than the others, so that manifold will have to come out again. The trouble is that the manifolds and butterflies are all clean and I have heard people say that they are a pain to seal up again when clean.

Engine mounts,

This is the new design, it uses the original bracket with heavy box section and a tube welded on the end for the bolt to pass through to the new rubber (Jaguar E-type)

The pic below shows how much the rubber has sagged and the new bracket behind it prior to being tacked in.

I fitted the newly modified engine brackets and I am pleased to say that so far there is no noticeable increase in vibrations or noise from the engine.

All the butterflies in the inlet manifolds fit a lot a better now and other air leaks from the top of the manifolds have been sealed off, so I can have the engine tick over at 600rpm again if I wanted.
Driving around, I can sometimes hear a knock from the back and some of the blue Polybushes fitted do not look as good as they should, so I will probably end up replacing those with Superflex ones.

The next area I feel I should concentrate on is air delivery to the inlet manifolds. All of the components for this need a good bit of thinking through, the basic plan though is to have a box over the manifolds, fed by colder air from the front of the car.
Considerations to be made;

• Air box backplate buy or make? - Both ITG and Pipercross sell them for around £30, but they are only pieces of alloy sheet with fasteners
• How to secure the backplate to the ram pipes? - Again ITG sell these, but £8 for a grommet
• How to seal the backplate to the air box? - Adhesive foam? rubber?
• Where to route the pipe/s to the air box
• Where/how to induct air into the pipe? - Under the radiator, but not so low that it picks up water?
• What size pipe/s to the air box? - I'd like to have two feeds so not to starve one end of the engine

I've seen Pipercross and others sell air boxes of a suitable length, but at over £200, I'd rather make my own from fibreglass or Carbon Fibre and have something that is exactly what I want.

I've been going through some more of those finishing off jobs. The Facet low pressure primer has now been replaced with the pump from George, fortunately it has the same mounting centres as the previous pump, so it made for easy fastening down and I now have two quieter rotary fuel pumps.

The search for the elusive speed vibrations have led me to reduce the gap between the bonnet and sill on the passenger side, so the bonnet assembly no longer vibrates as much at speed. In addition to this, the rear tyres have now been replaced with Conti Eco Contacts and doing these two things have really made the car much more steady.

Had the Bank Holiday over in East Anglia, which meant doing a bit over 400 miles in the GT6, the miles just flew by and it was a pleasure to drive, much changed from 18 months ago.

Unfortunately my camera did not get any video from the last rolling road session, but I have put together a video from footage collected by Alex at Maynards. GT6 PI on the rolling road

Rolling road time again

So we had a long afternoon at the rolling road, where we did runs with the GT supplied head and again after changing the later CR type inlet manifolds for the earlier CP manifolds, which have be machined out to enable the CR throttle spindles to be fitted. Ram pipes have also been fitted to the new manifolds to increase the inlet length.

Torque

Power

Blue run is prior to the head change, but still injection and CR inlets.

Green run is with the new head, but still injection and CR inlets.

Black run is new head and CP inlets and ram pipes.

It is clear to see the improvements with the new higher compression cylinder head, giving more power and for longer and the CP inlets giving an extra eight or nine BHP. The engine is still fitted with the relatively mild stock MkII camshaft.

Surprisingly the fuelling is still alright everywhere apart from idle, giving figures, if I remember right, of 3.8 to 4 over the rev range.

I've still a bit of fettling to do to get the inlets to match the ports properly as we were running out of time and I also need to consider making a cold air feed as it does seem to be quite sensitive to temperature.

I'm pretty chuffed with the results, it's all taken a fair bit of time to get this far and I'm sure there is plenty more to be done, but it has given me the ability to see the improvements and gains by fitting the right parts. Also interesting to see how much can be done with a stock camshaft, goes to show that some of them aren't all that bad.

I'll probably end up fabricating a custom air box to give plenty of space around the trumpets and have a couple of cold air feeds. There are air filter baseplates approximately 500mm long, which would be perfect for this, but the filters that fit onto these are around £125, so I may buy an un-drilled baseplate and fit my own box onto this and have filters in-line or at the end of the cold air feeds.

New towers and head fitted

Got the modified suspension towers fitted in the week, though I still have to fit the wiring and coolant pipes back around them and I'll leave the steering column out until I have changed the head. Not the easiest of jobs to do with the engine in place as you of course have to have the chassis on stands and then support the engine as you swap the towers over. Having the single multi-way plug on the steering column made it a doddle to remove.
Next job is to check torques, fit the wiring and coolant hose back in before checking the starter and swapping the head, then I could thing about finishing off the new engine mounts.

Then it was time for the head change, the old head was removed quite easily before cleaning off the block and a new Payen head gasket fitted before re-fitting the starter and water pump.

So I got the GT6 running again on Saturday with the new head on. Took me a while to get it started as the injectors needed priming and then I must have flooded it in a bad way, so I took the plugs out to clean them up and re-gap (should have done this when I went over to Megajolt ) and left them out while I went for lunch. On returning I wanged the plugs back in and it started up straight away.
With the new head it seems to rev much more freely, being all to easy to spin up to 6,500rpm, where before it was a bit of a struggle to get up to 6,300rpm. There is still a bit of a dip in the torque around 2,800rpm, but it soon picks up again, perhaps this could be ironed out on the rolling road.

Covered an easy 200miles in the afternoon on a drive over to Builth and found some good roads to drive once you get past the people pottering along at 45mph I'm not sure whether it's the car, me or both, but I feel a lot more confident driving the car now than when I did when it first went back on the road, just learning how to drive it?
One thing I did see from the run yesterday was that, despite the reasonably warm weather yesterday, the engine temperature was pretty well pegged at just over half way and the fan never came on, even in the slower moving traffic. Not too bad for a second hand pug radiator, but I may well change it for a new one as some of the cooling fins are looking a bit flaky.

It did reward me this morning by leaving a pool of brake fluid on the floor, a leak from the master cylinder. Fortunately I had a spare master cylinder, but the lid will not unscrew, so I exchanged the piston with seals and re-bled the system and it has been fine since. Makes me wonder if I ought to get in a spare set of cylinder seals just in case.

The next job to do is to finish off the new engine mounts, really don't like the look of the existing ones and how they are cracking.

Head, pipes and towers

I did not buy much at the Triumph show at Stoneleigh earlier this year, but I did collect this:

It's the replacement head re-worked by GT, complete with a set of his valves, a job which he managed to turn around in quite a short time before heading back home. It has been buretted and it looks like the compression ratio is 10:1. My plan is to have another go on the rolling road after fitting this to see what effect it has had, then fit different inlet manifolds while at the rolling road and adjust the Megajolt as required.

My attempt to fit the better hose clamps hit a problem last week, the home-made take-off on the bottom hose was not wide enough to get a proper seal with the wider clamps, so it started leaking.  To get round this, I bought a ready made tee piece from Car Builder Solutions, hopefully it should seal better with this.

Over the weekend I finished modifying the other suspension tower to take the alternative engine mount and then gave them a clean off and paint, ready for fitting soon.

I've decided to crack on with these towers again as to fit them requires the cooling system to be drained as a hose passes through the one on the passenger side and it needed to be partially drained to change the head anyway.

PI fuel system, again, and coolant clamps

Bit more progress over the week, which I have been able to finish off this weekend, the fuel swirl pot is now fitted.

At the same time, a bracket has been found for the large fuel filter, it turned out that a wiper motor bracket is just about the right size for my filter. So what we have is the low pressure Facet pump supplying fuel to the bottom of the swirl pot, fuel exiting the bottom of the pot to go to the filter and high pressure pump, a return from the pressure release valve (PRV) going to the top of the pot and a outlet from the very top of the pot to the fuel tank, through which air and excess fuel is bled out.

I've been out for a run since fitting all this up and it works fine, but the only issue I have had is the lack of pressure for the Facet pump to work against. The problem is that these solid state pumps get very noisy when they do not have a sufficient pressure to work against, so I have clamped in a piece brake pipe in the return to the fuel tank to restrict the flow. This has quietened it down a bit, but I don't want to restrict it so much that it won't be able to clear the air fast enough when it really needs to.

With this recent talk of cooling systems and leaks it reminded me that I had some misgivings about one or two or the hose connections and it had been my plan to change the hose clamps. So today a set of eight Mikalor clamps turned up in the post, should get them fitted tonight.

They should hopefully provide a better seal than the thinner jubilee clips and actually work out cheaper than stainless jubilee clips from Car Builder solutions, these were £1.17 each

I've been using Mikalor clamps on exhaust systems for a few years now, but they do seem to have got a lot cheaper and easier to find now, no need to spend over £5 each now.

I did think about the potential for warmer fuel from the PRV getting back to the pump before going to the tank, but seeing as it enters towards the top of the swirl pot, is warmer (so more likely to rise than sink to the bottom of the tank) and that the low pressure pump is at the same time pushing an excess of fuel up though the swirl pot outlet, it should push that warmer fuel back into the main tank. I guess I will have to wait until we get one of those hot days to see how it copes.

Smaller jobs and settling down

So I got a few more jobs done in the week, rear brakes re-assembled and hopefully setup right this time and a bit more sound deadening has gone down on the gearbox tunnel before the carpet, which of course has to be modified. I've been trying to go round and finish off some of those jobs I started a while ago or have bought parts for, but never got round to fitting  to this end, the car now has a Spitfire front spoiler.

At the same time I have been working on the fuel system, again , and have been looking at fitting a fuel swirl pot I bought some months ago. To give me some extra freedom of where to position it, the outlet and bleed-off tails were cut off before being re-tapped to take a 90 degree fuel union and sealed with JB weld for good measure. This means I can run the swirl pot much higher, giving a greater head of fuel to the high pressure Lucas pump.

I then had a chance to take the car out for a run and I am pleased to say that the majority of the speed related vibrations have gone. There is still some vibrations coming through the steering column, but at the same time the whole of the dash is vibrating, so this could be related. At the moment the 'H' bracket is not in place between the dash and the floor/gearbox tunnel, so I might have a go at modifying a bracket to fit. It's been good just to get some miles in on the car and try to get the feel for it, after driving Spitfires and the 2000 driving the GT6 is so different with the increased power and the ability to corner, though I have not found the limits yet, probably more down to the driver.

The car seems to have bags of torque, just driving around choosing the quieter road, I was sat behind a car doing 50mph till he jumped on the brakes for an even slower car in front, a MG BGT complete with wire wheels and spinners, once the road was clear it accelerated beautifully in forth from 40mph all the way up to legal. I know I am never going to have it setup as well as some of the faster Spitfires, but it is still a hoot to drive and so much easier to do so with many of the vibrations done away with. Feel a lot happier about going out for a blast without tools now and would be happy to drive all over Europe in it, not something I would have wanted to do twelve months ago.