Throttle Bodies

April 13, 2008

With the Alfa finally booked in for paint (5th May!) and it going to the sodablasters next weekend, attention turns to how we’re going to build up the engine.

I’m really keen to keep the rorty carb “sound” of the old engine – its just a defining characteristic of an old sports car. There’s no way I was going to keep the fuel injection of the doner twin spark motor, so the Bosch Jetronic was one of the first things we binned after lifting the motor out of a Alfa 75 condemed to the scrapper by its rusty sills.

However, I’ve been coming round to the idea of throttle bodies, specifically Jenvy throttle bodies, which maintain the sound of old carbs (and look pretty similar) but use modern injectors and an ECU for very accurate fuel delivery, and mean you can get massive power and a well-behaved engine when pootling about in traffic.

Image © Jenvey Dynamics

Combined with an Emerald K3 from engine management guru Dave Walker, these puppies should be good for 200bhp and beyond.

I suppose I can get some of the not inconsiderable funds required to purchase them from selling my old Dell’orto 45 carbs on the ‘bay.

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Eaton M45

April 6, 2008

Hmm, I wonder if this can be used in my Twin Spark rebuild?

Eaton M45 Supercharger

Alfa update

March 22, 2008

It’s been some months since I posted on the progress of my Alfa build. There’s been a fair bit more welding – rear panel and inner/outer arches plus middle and outer sill on the offside in addition to those on the nearside since my last report. Although its been a touch expensive at least I know the car is 100% steel and the repairs should be good for many years to come.

One positive to come out of this was an opportunity to sort out once and for all the fit of the driver’s door – the gap between the bottom edge and the sill was always too big (around a half inch) and it didn’t sit too well with the b-pillar. Now we’ve replaced the outer sill properly, the fit is much better, and Pete (aka weld-o-man) took to opportunity to roll back some metal out of the rear wing and butt-weld the seam back up to get the b-pillar to door gap looking just right.

Meanwhile, I was tasked with stripping everything from the car. Seeing as I’m never going to have the car in this many pieces ever again (engine and gearbox out, pretty much the bottom 6″ of the car replaced) I’m going to take the whole lot back to metal and respray it inside and out. This means I’ve spent about 3 weekends stripping the whole interior, wiring loom, hydraulic lines, exhaust and all the trim off the car so it is now a bare shell. The photo shows the car halfway through this process (you can see the brake servos are still in).

The loom came out in one piece and looks in pretty good condition – I’ve managed to keep the stalks and the buttons attached so re-fitting it shouldn’t be that difficult. The hydraulic lines, however, were a complete nightmare and I resorted to cutting them in places – so much corrosion where the lines enter under-floor master cylinder that trying to unfasten the unions resulted in them turning to brown dust. As the lines were all steel, they could do with complete replacement with copper items which won’t rust.

I also took the opportunity to ask Pete to weld in some proper seat mounts – the existing arrangement consisted of bolting the buckets to universal Sparco mounts bought from Demon Tweeks, and then bolting these in turn onto the captive nuts (mounted on the floor pans) that held the old runners. After a quick personal fitting, with the seat roughly in place thanks to two antique blocks of wood (Pete’s main business is restoring old French furniture) he welded two hefty cross members (per side) between the inner sills and the transmission tunnel. The universal mounts now sit on these instead. Much safer in the event of an “off”.

So, although it looks like complete shit at the moment, the project is actually coming together nicely. With just wheels still attached so the shell is mobile, the next step is getting all the paint and old filler blasted off and then it’s ready for a fresh skim of P38, prime and a very neat paint job inside and out. Then comes the tedious job of a re-fit.

Meanwhile, batman is having a tinker with the engine side of things. He’s making noises about throttle bodies and re-using the actuator from the doner engine that can alter the cam timing with revs – a primitive form of variable valve timing – we could end up with an engine pushing near or even over 200 ponies at this rate. Now the car’s got some metal in it making it nice and stiff, this is shaping up to be one cheeky little track weapon.

Full photoset of latest progress here.