This sounds a silly question and I probably can guess the answer but here goes anyhow... I have twin weber 40 idfs, running 60 idle jets. If I swap them to 57 idles, will I need to adjust the idle control? Thanks
It's a 1776 but despite 2 rolling road sessions, that is the size that worked best. I posted up another thread a while back regarding fuel economy and know that in part my fuel economy is linked to these idle sizes. I know eurocarb recommend 55s but it always seemed to not run right on them. My last trip to rolling road place saw the mains being increased which made huge difference to performance and drivability. I decided to get some 57s to give them ago. Thanks for replying though I do appreciate it.
Give me the engine spec... and the choke size in the carbs are they new carbs, or old ones? as I've seen old ones furr up in the fuel galleries due to a lack of use at one time!!
Thanks.... The engine was brand spanking new 3 years back and hasnt done huge mileage (9k). I had some problems shortly after it was built due to a faulty distributor which caused some issues. (a whole another saga!) Then it dropped a valve last year requiring a rebuild by Laurie Petit...(what an absolute legend he is!) So Engine is a 1776 with genuine Twin Weber 40idfs. These were supplied by Eurocarb on the basis it was for a 1776 motor in bay window. Emulsion Tubes F11 Air Correction Jets 180 Main Jets 130 Idle Jets 60 Choke Size 28 The idles they provided were 55 and the mains 115. Engine never quite ran right with idles off 55. After a recent rolling road the mains were upped. Not sure what details are useful but here goes.... AS 41 crank case (machined and tapped) heads are euromax (as reccomended by laurie) - nice casting apparently! 69mm Crankshaft Camshaft (W110) Deep sump External 13 row Cooler 123 Distributor Running VW Speedshop Stainless Side exit system. I dont really have a lot of other details for the internals... Thanks
No stress... just gives me a reference as to what size the chokes should be!! It does seem a little odd... what did the guys at the rolling road say about the jetting? did they have any ideas as to why it needed to be so large??
To be honest they thought it strange, but couldn't really offer me an explanation. When the bigger mains went in and the van had the right pull and no flat spots, they seemed happy to suggest that was it. "every engine is different" is what they said, and just because eurocarb jetted them as 55s didn't mean it was going to be the same for every 1776. I certainly not an expert, but have asked around and it seems the idles for 1776 vary from 50 to 60 Having got the van seemingly right on 60s I thought would try going back down in size. I can't really afford to go to another rolling road so figured changing jets for 15 quid was a good option
Yeah... this is why I tell anyone who fits twin carbs that they need to get them set up as you can't really go on book values!! you can get a set of Jet drills... so technically you could start with a 50, and slowly open them out until you reach the optimum size!!
Hmmm jet drills.. That's an option I guess. Ebay perhaps? So I guess I can swap the 57s in and try it with no idle adjustment then. Thanks for help.
Although I think I need to do some more hunting, as the jet drills I can find at the mo, only go in 0.05mm steps...
http://www.ebay.co.uk/itm/20-PIECE-MICRO-HSS-TWIST-DRILL-BIT-SET-CASE-0-3-To-1-6mm-SIZE-BITS-NEW-/230827044829?pt=UK_Home_Power_Air_Tools&hash=item35be5d2fdd
Are the accelerator pumps working correctly? If not you will get a flat spot and this may be compensated for by the larger idle jets.
