Episode 14 of Retropower’s Gordon Murray Mk1 build catches up after the car returns from having its exhaust made. With the exhaust fitted, a chain of waiting jobs could finally move: the dry sump tank, the last plumbing, and the start of the interior.
Video: Retropower on YouTube · watch “Gordon Murray's MK1 Escort - Retropower Build Episode 14” on YouTube
What happens in Episode 14
Behind the scenes at BTB (0:58). The exhaust was made from manifold to tailpipe by BTB. They work with a CNC tube bender. Primaries were trial-fitted in the car, tweaked in cardboard and measured with a portable arm, aiming for equal lengths at the target length while clearing the oil tank.
The finished system (8:58). Cosworth specified the pipe dimensions: 2-inch primaries in a 4-2-1 layout, with a 2¾-inch pipe running back. The car is built to meet modern emissions rules, so there’s a catalyst in the downpipe. BTB also made a straight delete pipe that clamps in its place. The smaller of the two silencers, ahead of the axle, also has a V-band-clamped delete pipe. Gordon wanted to hear the exhaust, so it can be made louder if needed.
Dry sump tank (10:33). The tank has three machined billet parts, made from Retropower’s drawings by a machine shop at Silverstone, with welded sheet aluminium in between. A threaded breather union anchors the top, so there are no visible brackets. Oil returns straight from the front cooler, hidden under the slam panel, and spins down a cone to shed air. It then lands on a baffle plate and drains into the tank.
Welding it in-house (14:08). Because the billet parts were costly, Retropower welded the tank itself. A press tool formed the corner radius to match the billet parts. The vertical seam runs down a corner, where the curve helps stop the aluminium distorting.
Plumbing and brakes (15:41). The tank and reservoirs were anodised, and oil-line fittings were on order, the last plumbing job. Brake lines were done: AP four-pot front calipers with 254mm AP discs, the biggest that fit inside the steel wheels, and Teflon-lined stainless braided hoses. The team put the mechanical side at about 95%.
Interior (17:50). A standard headlining went in and the fibreglass dash top was trimmed in Alcantara, with demist vents in polished bezels. Door cards and rear quarter cards are plastic instead of moisture-absorbing hardboard, ready for leather. The rear becomes a flat luggage area with two lidded compartments underneath. 3D-printed covers with a single knob reach the strut tops and damper adjusters.
Chrome, glass and badges (20:57). The car has new glass and seals, and re-chromed handles and boot lock. A run of enamel-filled cast badges, copying the Twin Cam wing badge but reading Cosworth, is being made with Cosworth.
Next (22:32). The car’s first public showing is at the Retro Rides Weekender at Goodwood on 18–19 May. The oil lines and the wiring loom are the main jobs left before it can run.
Parts, tools and suppliers mentioned
- BTB: CNC-bent 4-2-1 exhaust, 2-inch primaries, removable catalyst and silencer delete pipes, V-band clamps
- Billet and sheet aluminium dry sump tank with a de-aeration cone and baffle plate; anodising
- AP Racing four-pot front calipers and 254mm discs; Teflon-lined stainless braided hoses
- Alcantara dash top; plastic door cards; 3D-printed strut-top covers
Lessons for your own Mk1
- Mock up exhaust primaries in the car, with cardboard if needed, before committing tube.
- Make emissions parts removable if the car must pass tests but may also see track use.
- Put seams on a radius when welding thin aluminium, to limit distortion.
Mk1 context
A Mk1 floor leaves little room for a big-bore exhaust unless you cut a tunnel into it, so routing a 4-2-1 system past a dry sump tank takes careful work (Retropower comes back to this in Episode 16). Factory door cards used a hardboard-type backing, which is why Retropower switched material.
Related
- Series hub: all Retropower Gordon Murray Mk1 episodes
- Earlier: the Cosworth engine visit in Episode 5
- Background: the complete history of the Mk1 Ford Escort
- Next: Episode 15, the Retro Rides debut and first fire-up
- More builds on video: Mk1 Escort build videos