Category Archives: Uncategorized

Progress update

Uncategorized

I apologise for the lack of updates. It’s not dead, there has been significant progress…just no updates.

I’ll just leave a photo of some bling while I write up some more updates.

I tried so hard to save money on the fuel caps but they are kind of a defining external feature of the GT40. Unfortunately where I’ve seen people use Aston caps or similar they just look wrong.

I refuse to even consider what these cost me but I can take some solace in at least they were cheaper when I bought them than they are now.

 

 

 

It’s all very tyre-ing

Uncategorized

I’m currently in the middle of looking at suspension geometry but there is somewhat of an issue… that of tyre choice. So I’ve decided to tie down what size wheels and tyres I will be using.

I’ve already decided my wheels are going to be 8in wide front, 10in wide rear (or there abouts). I’m going to pick the most common cheapest suitable sizes. Tyre diameters are from here, tyre availability and prices are taken from blackcircles.

There are many reasons behind this logic.

  • More choice, the more original GT40 replicas are restricted to only a couple of tyres. With many manufacturers I’ve got the choice between going sticky and short lived or hard and long lived.
  • Cheaper. While running costs are not going to be cheap and I’m not going just on price the difference in 10mm width (or 1in dia) can be 100’s of £, see the difference below in the cost of a 275/40R17 vs a 285/40R17, 1cm wider but a new pair of 285/40R18 will cost £200-£400 extra!
  • Cheaper! Mentioned twice because if rear tyres are £100ea I’m not going to worry about ruining a set on a trackday etc. OTOH I may cry if they are £350ea!
  • Availability. If I get a puncture I want to be able to go to a garage and get a replacement. I don’t want to be in the position of having one tyre maker who do one run a year and there being no stock locally (if at all) or just not available any more (Ducati 906 Paso anyone?)

So onwards, lets look at what the originals used vs the modern SPF recreation. Now these are only one example as the GT40 used many different sizes in it’s race life.

Front originally approximately a 250/60R15 and a 225/50R15 or 225/60R15 used as a modern replacement.

Rear originally  approximately a 325/60R15 and a 295/50R15 or 275/60R15 used as a modern replacement.

So firstly I’m going to ignore the non-common (and original) sizes and work out the diameter of the remaining.

225/50R15 = 606mm

225/60R15 = 651mm

295/50R15=676mm

Lets look at tyre availability…

225/50R15 – two tyres, £80-£95ea

225/60R15 – eight tyres, £56-300ea

295/50R15 – one tyre, £375ea

OK, original sizes are out.  Fronts are cheap enough but no range and only one rear!

I want to keep the same “look” with the rears larger than the fronts so want to keep roughly 50mm (2in) larger on the back than the front.

Lets look at 16in wheels, firstly lets work out the recommended sizes (no stretch here!) using a tyre size calculator. For the front 8in wheel we have an ideal of 225 to 235. So lets keep it as a 225 for now.  On the rear we have an ideal of 265-275. Keeping the width and overall dia (nearly) the same the choices are a 225/45R16 (608.9mm, 4 tyres available, £96-£131ea) or a 225/55R16 (653.9mm, 74 tyres available!, £41-£135ea) for the front and er nothing for the rear, nearest can get is a 255/50R16 (661mm, 1 available, £387.29ea).

Onto 17in wheels, again the 8in front is recommended 225-235 and the rear 265-275 (max 285) here we have a choice of three, nothing that is near 606mm, nearest is a fair bit smaller. Choices are 225/35R17 (589.3mm, 3 tyres, £100-£152ea), 225/40R17 (611.08, 36 tyres, £68-£132), 225/45R17 (634mm, 166 tyres available!!!!, £44-£122ea), 225/50R17 (656.8mm, 116 tyres available, £51-£142ea). Rear tricky again choice of 255/40R17 (635.8mm, 21 tyres available, £73-£151), 255/45R17 (661.3mm, 7 tyres available, £143-£191), 265/40R17(643.8mm, 1 tyre, £131.59),  275/40R17 (651.8mm, 1 tyre, £174.09), 285/40R17 (659.8mm, 2 tyres, £268.59-£371.59ea),

Finally 18in wheels, same widths still.  front 235/30R18 (598.2mm, 0 tyres), 225/35R18, (614.7mm, 9 tyres, £106-£140ea), 225/40R18 (637.2mm, 90 tyres, £48-£99), 235/35R18 (621.7mm, 0 tyres) .  Rear 275/35R18 (649.7mm, 14 tyres £94-£238), 285/35R18 (656.7mm, 13 tyres, £156-£245), 265/40R18 (669.2mm,18 tyres, £106-£243), 275/40R18 (677.2mm, 10 tyres £179-£243), 285/40R18 (686.7mm, 1 tyre, £346), 255/40R18 (661.2mm, 31 tyres, £79-£187)

OK. We now have a lot of data and the chosen results are…..

Front 225/40R17. Not the cheapest, not the most available but in a pinch I could fit a 225/45R17 (gain 11mm front height) or a slightly wide 235/40R17. The 18in wheels just didn’t have small enough tyres available.

Rear 255/40R18. A larger wheel on the back mostly as more suitable sizes. Slightly narrow and the cheapest tyre this time but spot on sized at 50mm larger diameter than the front and as I’m “only” going for ~300hp a 255 rear will be fine.

 

 

 

 

 

 

 

 

 

 

 

New pages

Uncategorized

Added a parts page, suppliers page and two links page.

Parts page, generic links page and suppliers page is a bit bare at the moment but I’ll fill it up.

Comment if you want your build log or page linked.

View them by clicking the relevant link on the menu under the title bar or just here Links or here Parts or here GT40 Links.

 

Engine Update

Engine, Uncategorized

So, last post I had an engine and a gearbox and an adapter plate but no pictures of it in the car.

I did paint the original inlet manifold, piss about trying to get it to fit with the original distributors, ECU etc then gave up.

Plan now is ITB and COP (Coil On Plug) using Lexus IS200 / Landcruiser COP part number 90919-02230 along with proper plugs (part number 90980-11885)

Wiring to the COP is via 20AWG MIL-W-22759 spec wire which is insulated with extruded Tefzel (ethylene/tetrafluorbethylene) and unlike standard thinwall which is only rated for 105°C it has a maximum temperature rating of 150°C.

The ITB setup was originally planned to be two sets of GSX-R1000K1/2 throttle bodies  on custom manifolds but I changed my mind and bought a set of OBX ITB’s. They still need a load of work but far less than making my own manifolds.

They use the original injectors but the injector rails don’t fit. I’ll need to modify or get new ones made up.

ECU is now going to be a Megasquirt MS3 + MSX. Fully sequential injection and ignition. Sensors will be the original crank sensor plus one of the cam sensors.

I have decided to run the thermostat at the front of the car. So the thermostat “bottle” has been lost (partly as it impacted on the bulkhead) which means an adapter needs making up.

The original front water bridge impacts on the bulkhead and had a massive hold in it where the bypass originally fitted. So I need adapters into the head and to run a T piece.

So then I looked at the clearance to where the rear exhaust downpipe would run….

and then I looked at the chassis…. and I looked at the angle grinder….

 

 

Engine adapter plate

Engine, Gearbox, Uncategorized

The engine to gearbox adapter plate turned up at the w/e

Along with the oil-take off plate/block

So despite the sub zero temperature in the garage I had to at least try out the adapter on the engine (the gearbox will have to wait until the snow has gone!)

So put it on and shock horror, it didn’t fit…. it hit the flexplate/starter gear.

After a second of panic, thought “hmmm, is there a spacer”, checked the manual and yep one spacer, so off with the flexplate, remove the spacer and try again. Now it fits (although I need a another dowel as one was missing).

I guessed that the starter will have to be moved back an equal amount and Doug confirmed it, he also mentioned that the starter motor bolts will have to be shaved to fit. Still, have lathe, will modify! 🙂

Next job is to get some M12 bolts (I believe to make matters more awkward they are fine thread) along with some studding and I can mount it properly and attach the gearbox. Plus I need to make up a new dowel.

ABS TCS DSC and EBD

Uncategorized

I had a nice idea of fitting a Bosch ABS5.7 system into the GT40. I’ve given up on it. I just don’t have the access to the system I need to make the changes I’ll need and its just too safety critical to bodge it. Without getting too technical essentially I’d need to ‘tell’ it about the type of brake calipers as well as how fast it can slow down (under ideal conditions). That’s just for the ABS/EBD. For TCS and DSC I’d need that plus it to integrate it with the ECU/PCM as well as cornering ability to steering angle, roll rates and a whole load else.

I plan instead to add the bits that the system would need, ie the sensors and route the rear brake lines individually (normally it would be a single line to the rear and then a splitter). Then if at some point in the future I can justifiably afford a Bosch M4 I won’t need to dismantle and rebuild half the car to get it in!

That then still gives me the option of tracking wheel speeds, steering angle, G, roll and yaw.

Second Panel

Uncategorized

Bit happier with this second one. Although it has been suggested that I use an angle grinder with a thin cutting disc. I’m limited to the times I can do this however so this one has also been done by hand.

I’m pretty much decided that I’m going to carpet the interior.