Who knows Webers?

With my Elan on the road again I have one issue. The car runs great with no flat spots, good idle, etc. However, it runs a little rich as the spark plugs and tail pipe suggest. This car was originally brought over from England, to British Columbia, before making its way to the Tahoe area. Because my house is at 6500 ft and I'll be driving it anywhere between sea level and approx 7500 ft, I need advise on jetting. Most of the driving will be between 4000-7500 ft so it makes sense to tune it for that. Is there a rule of thumb for reducing jet sizes based on elevation differences. I'm assuming it is correctly jetted for sea level now. Any help is appreciated.

I can't advise much on jetting of Webers but I have a couple of issues of Practical Performance Car (a UK mag that's pretty close in spirit to GRM) where they discuss setting up sidedraft Webers.

I can try and find them if the articles might be of use.

BoxheadTim wrote: I can't advise much on jetting of Webers but I have a couple of issues of Practical Performance Car (a UK mag that's pretty close in spirit to GRM) where they discuss setting up sidedraft Webers. I can try and find them if the articles might be of use.

Sounds good. If you find them, I think you have my email.

,Russ

Try giving Dave Bean a call. I have dealt with Tom on matters concerning my Cossie, and found him to be UBER Helpful.

Leo

I have one issue. The car runs great with no flat spots, good idle, etc.

Ain't it awful when they do that. I would be cautious of trying for perfection and this may be as good as you can get it. I would buy (local auto stores sell them) a few sizes down and experiment since each engine and carb will not be the same anymore. Also test it both at speed and around town since driving also affects the plugs. Set for it higher speeds since too lean can do nasties at higher speeds. Nice Lotus! Cheers Ron

I'll probably start by going one jet size smaller and see how that works. I don't want to make more than one change at a time or over compensate on the jetting. Nothing worse than creating a problem and not knowing which change was at fault. It does need to be a little leaner though for my elevation but I don't want it so lean it I have to make jet changes when driving down at sea level.

What really interests me is the possibility of going to fuel injection. I know it's not difficult to do, but the cost is an issue along with not having that pair of sexy side drafts to look at when taking the bonnet off.

There are companies that sell EFI throttle bodies that look like Webers.

http://www.webercarburetors.com/ppw/html/throttle_bodies/Throttle%20bodies_dcoe.htm

Ian beat me to it...If cost is not an issue, you can go Weber-like injection. There are shorter units if space is an issue such as a Morgan, as well as the standard size. Quite slick.

Leo

First off - what kind of Webers? That there's more than one suggests DCOEs but it doesn't completely rule out any of the gazillion other carbs they've made.

Assuming DCOEs, the hard part is that the throttle opening range of every circuit overlaps 2 others. Some affect the total aggregate fuel volume. Often it's the emulsion tube and not a jet at all.

A very good reference is:

The Big Weber Carb Book

Get it. Then verify valve adjustment, ait filtration cleanliness, fresh plugs, timing and dwell all set. Fresh gas too.

Then do what the book says. My Sprite w/ a DCOE took a while but it's ~perfect~. I ended up running exactly what Mike Pierce at Pierce Manifolds suggested with maybe one or 2 orifices a 1/2 or increment one way or the other. He really knows this stuff and is very helpful. Call him and ask - he'll give advice off the top of his head that's spot on.

Webers are 2 DCOE 18's, I have fresh gas, plugs, wires, timing is correct, etc.

Etubes, jets, venturi's, are to factory spec. I have 2 books on Webers including the "Big Weber Carb Book" They are both filled with very good Weber info, theory, etc., but both fall short on certain tuning info. Bottom line to tune them properly requires dyno time and/or road testing. I'll do the later first and dyno as a last resort. I'm ready to tackle it, and will report back on what I discover. Since I've never played with DCOE's before my findings may or not be useful to others, but I'm hoping to at least learn some general info on altitude tuning and adjustment.