mettersl wrote:Hi,
My atmos has been undergoing repairs at RATS and is about to start the reassembly journey. I want a reversible carb change and the DGAS seems a good choice. If you have the jetting for them, that would be really helpful. Are these cars otherwise std...heads, exhaust etc? Mine is at present , but I'm contemplating some changes, but want a reliable set up and a car that won't need much more than standard maintenance when finished.
Did you go for electrical or hot water choke, both seem to be available, but the how water one seems to be a more predictable option.
Thanks
Lee
Hi Lee
Sorry about the delay replying
My Blue car has modified heads (planed, ported, and ccd). The heads actually had about 1.5mm planed off them, and the head guru increased the size of the combustion chambers a little to compensate. This means the cams are actually slightly advanced, as the engine doesn't have adjustable cam gears. The car goes like a cut cat.
The black car is in the engine rebuild stage at the moment. Heads were really carboned up. They are getting the same port job as the blue car, but with only about 0.5mm planed off to keep the cam timing a little more sane. This car is also getting a set of headers manufactured for it, and will run through a pair of resonators. The car always had a reputation for going better than average according to other owners here at the time I bought it (the car came with an aftermarket freeflow muffler that looks standard but doesn't sound it). We expect is will go a lot better than the blue one once completed.
You need the larger DGAS, 38 rather than a 34. Both of my cars have the water temp controlled chokes - they are straight forward to plumb in to the original Solex circuit.
My Blue car has 45 idle jets (what your carb will probably come with), 142 mains and 185 air correction.
They are really easy to set up. Ensure the engine is warmed up and the choke fully disengaged.
Use the jet sizes above as a start point, back off the idle screw until it does not touch the throttle lever, (snap the throttle a couple of time to make sure the linkage is fully closed), then turn it in until it just touches the throttle lever and then turn it a further half turn - no more.
Then set the mixture screws by screwing them in gently until they just seat, then back the off one and a quarter turns. Start the engine, and with it idling at operating temperature and the choke full open, gently turn each idling screw in until the engine just starts to run worse, then back it out a little at a time until you reach the sweet spot, or until the screw makes no difference - then turn it back until you get the sweet spot again. If the mixture screw has been wound out more than one and a half turns, the idle jet is too small (lean), and if it is three quarter of a turn or less, it is too large (rich). This all assumes the idling screw is not more than half a turn in.
Float level is important too - if there are signs of richness or flooding, the level is probably too high. Plastic floats should be 18mm from the gasket surface to the top of the float (don't depress the needle valve ball and string when measuring), then set the float drop to 2mm maximum. fuel pressure should be no more than 3psi.
All of this setting of the idle screw at half a turn in is critical, because if the enrichening holes are exposed at idle, the car will be rich at idle and will stumble at around 1800 rpm when you boot it hard.
Once the idle is set up, you can fiddle with the main and air correction jets is if leans out or is too rich at higher revs. I'd suggest a tuner do this, although you can experiment using a mate with a stopwatch or the seat of your pants. But the main and air correction sizes noted above should be pretty close.
With respect the the standard manifold, porting and accurate matching to the head is the answer.
I hope this helps.
Cheers and Speed Safely
Graeme
by Custard » Thu Jun 16, 2016 6:15 pm 
