August 2014

A momentous month of progress culminating in finally having the car dyno-tuned and on the road.

Earlier in the month  the interior trimming out of the Marcos began with lots of paper templates, messy contact adhesive and stretchy boat carpet. The sills and kick panels were done first so that the door seals could be put in place, then the rest of the trimming followed. It was a bit of a issue sourcing the correct profile of  door seal rubber that would not only fill the gap between door and frame, but also stay firmly attached to the fibreglass door flange. Once the door seals were on it was possible to refit the door check straps and an old spun aluminium external bullet mirror which I’ve had in storage for at least a decade waiting for a suitable classic to fit it to. Once the carpets in the front half of the cabin were in, the seats could be fitted, and then it was a matter of nutting out a couple of removable carpeted boards made up to cover the spare wheel, battery and fuel tank, whilst still fitting in and around the roll bar. Without the glass in place most of the rear trimming was accomplished through the rear window. Then a  pair of matching harnesses were clipped into place on the roll bar and some fabrication of seat belt mounting plates began that would safely and securely anchor the lap sections of the harness through the fibreglass body shell . Apart from the interior door panels (an original pair of fibreglass panels were picked up recently on UK EBay), the trimming of the Marcos was then complete. It’s amazing how much material is used and how many separate panels needed to be made up.

Fitting the fitting the front and rear screens and rear quarter windows was a real effort which I was glad to hand over to Gavin of Protector Autoglass. Some trimming of the bodywork windscreen flange was required before the new windscreen ( a pre-loved unit from New Zealand complete with sports car club sticker) would fit and all the window seals are fitted with a black rubber locking strip at this stage instead of the plastic chrome one. Once the glass and rubbers settle into place a chrome locking strip will replace the black rubber ones. With the windscreen in place, a suction mounted rear vision mirror and the windscreen wipers were fitted.

Monday 18th August – Big day today. Inspection and registration (Historic Club Permit) completed, number plates fitted and we’re now road-legal.    Even found somebody to insure her . With confidence running high after an initial 60 mile shakedown on the road, the Marcos was signed up for its first competition event, the Geelong Revival historic sprints in November.

After the initial shakedown, a few minor issues surfaced. A small oil leak from one of the oil cooler hose unions was easily fixed, as was a spongy brake pedal (later found to be caused by a not-quite-tight-enough pipe fitting at the master cylinder), one wiper lifting off the screen at speed needed a stronger spring, the engine breather hose needed to replaced and repositioned after drooping down when hot and melting on the exhaust manifold; and probably the most annoying –  the sliding windows in the doors being unable to remain tightly closed, especially over bumps and irregular surfaces.
I’d noticed some holes on the interior side of the window frames which I figured was for some sort of clamping device, but couldn’t find any information or pictures on what was missing so decided to make my own.
The knurled bolts are the side-screen fittings from my Bugeye Sprite and the aluminium bosses were turned up on my lathe. They have a rubber insert at the base that acts like a nylock nut, and the knurled bolt pushes a a rubber plug against the glass inside the channel to hold the glass in the desired position. After another 70 miles today the problems seem to be mostly overcome – although the wiper is still lifting off the screen at over 80mph

With the car now having covered about 150 miles, it was booked in for a dyno-tune to set the Weber up properly, check the timing and so on.  I warned my dyno guy (who is on the larger side of svelte) to start doing some limbering up exercises in preparation for getting into and out of the car.

In the mean time it was back to the door trims – I thought (and hoped) that all the fibre-glassing and filling was well behind me, but the pair of old fibre-glass door cards that I picked up on UK EBay needed a bit more than the simple clean up that I had hoped was sufficient. Apart from the large holes for what I presume were window winding and door handle mechanisms, there were several large chunks missing and of course all the self-tapper holes around the perimeter don’t line up with the corresponding holes in my doors. So, out with the matting, resin and fillers to bring them back to Square One.

Wednesday 27th August was a long and expensive, but productive day today at the Dyno shop.
The Marcos was trailered down to the outskirts of Melbourne (about 100km away) where, even before starting it up, we found a problem with the float on the 45DCOE Weber.  It should more correctly have been called a ‘sink’ as when checking the float level it was found to have a pin-hole leak and was half full of fuel – that explained the overly rich characteristics shown during my running-in sessions .
A new float, needle and seat and a different bleed-back valve were fitted. Then an oxygen sensor fitting was welded into the exhaust pipe just aft of the final 2 into 1 collector and a tangle of umbilical cords were hooked up to measure the mixture,  fuel pressure, air temperature, coil output and we even found a spot for a knock sensor.  The car was strapped down and given the first of many runs through the gears and up to 7000rpm in top.  The first run showed promise, but the old SU fuel pump couldn’t keep up with fuel demand and actually showed negative fuel pressure readings from 4500 rpm upwards – a sure fire way to melt pistons at somewhere like the Philip Island GP circuit. A portable fuel rig was hooked up and plumbed in ,and the difference was amazing. The fuel pressure was constant and the engine kept developing power up through the rev range.

We worked our way through through various jet changes to try and overcome a flat spot at about 2500rpm where it was indicating an overly rich mixture, but eventually fixed it by dropping back a size in the auxiliary venturies. That gave us an excuse to richen up the top end again where both torque and horsepower benefited.
With good reliable figures across the board we stopped playing with engine and decided to replace the old stuffed SU fuel pump with a new Carter pump and an adjustable regulator – the same set up that was on the fuel rig we had been using since the first run.
Phil (the dyno guy) was suitably impressed with the Marcos and especially the torque developed by the motor.  On the graph below the torque is the blue line (maximum was 71.2 ft-lb at anywhere from 3700 to 4600 rpm. Horsepower is the red line and it peaks at 75 bhp at 6200 rpm. These are at-the-wheels figures so the flywheel output would be significantly higher. The black line is the air-fuel ratio which remains in the 12:1 to 14:1 range throughout.

It was a long day, I arrived home just on dark, but I feel confident now knowing that we’ve optimised the setup and fixed a couple of potential disasters that would have cost me more than just a day on the dyno.

The door cards are still waiting to be sanded back, trial fitted and trimmed, and then we’ll just about be finished !!