|MAIN HOMEPAGE||ZENITH HOMEPAGE|
|OVERVIEW & CROSS SECTIONS||SPECS & ADJUSTMENTS|
|INSTALLATION & REMOVAL||STRIPDOWN - PAGE ONE||STRIPDOWN - PAGE TWO||STRIPDOWN - PAGE THREE|
|Venturis all ready and waiting for you to spend endless hours trying to balance them and make it run something like it is supposed to!|
|Before starting your engine set mixture and air bypass screws on the carbs to base settings as described in the specifications and adjustments section. This is mixture screws 2.5 turns out and air bypass all the way in.|
|Then follow the instructions on balancing! This is far more complex than the few lines of text in the manual may make out. Just getting the thing to run at all well enough to get a stable idle is the first challenge. If you can get it started keep it running on the throttle and go for a drive to properly warm it up. If it's not properly warm the final set up will be all over the place. The ignition needs to be set up correctly so before you spend too much time on detail carb set up, get the dwell and timing set correctly. I warmed it up on my way to Sainsburys and then did the set up in the car park under a street lamp at 9:00pm! It takes ages and all the reving of badly tuned engines will not keep your neighbours happy!
I found that it was necessary to raise the idle on the stops to 1500rpm to get a stable reading on the syncrometer and keep the engine idling long enough to set it up! If the reading is moving too much then bring the idle up further to smooth things out. With the cross linkage disconnected adjust the stops to get matched airflow in 1 and 4 (with the bypass still closed). Once these two are balanced you can start working around the other four.
Note which venturi is flowing the most air and then open the air bypass screws on the others to match it. You will notice the idle speed rise as you open the screws, so go back to 1 and 4 and bring the idle back down on the stops whilst keeping the airflow across the banks balanced. As the engine gets closer to a proper set up it will smooth out and you can lower the idle back down to 1000rpm. Go round again and make any further tweeks. As you had the throttle slightly too far open to get it running it would have been breathing through the transition ports so it is important to make the final adjustments with the idle speed close to the book setting.
Now the mixture....
I used a Gunsons gas analyser from Halfords. Not probably the most accurate device, but it did the job and the digital tacho and dwell meter was really useful during the basic set up.
The book says 3% CO. Well it ran at this setting, but hesitated and was a pig to start. Winding the screws out another 2 turns each put the CO at more like 6% but the overall running was vastly improved. Just wind all six screws out by 1/2 turn at a time and let it stabilise before checking.
Hopefully things will have improved massively by now, assuming of course at some point you've checked your float levels and matched the accelerator pumps as well.... You did didn't you? :)
I hope you have used these pages and found them useful, any comments or suggestions are welcome. You can normally find me lurking on the forum www.ddk-online.com under my ID of Gary71. So post any questions on there and I'm sure one of the members with more experience than me will help out!