This is gonna be a long post so sorry in advance!
Right, this is a follow on from some of my previous threads. Basically I have restored a 2 litre a/c 1981 engine, with a weber single carb 32/36 DFEV.
Initial problem - Engine would idle ok but would hesitate and stall under acceleration(accompanied by backfire/deep noise), and when driving would stall when clutch was in. Engine has had new fuel lines/filters. Would get backfiring through carb with acceleration. Adjusted ignition timing to 7.5 BTDC as weber has only a vacume advance. Very little effect. Spark plugs examined and found to be black (brand new plugs). Suspect overfuelling.
Solutions tried - Removed carb and full stripdown/clean of all jets. Internals found to be in good nick, all diaphrams in good condition. Some dirt that is blown out with carb cleaner. Cant seem to remove emulsion tubes but given a good high pressure blast. Float heights set as the two plastic floats appear twisted, one sitting lower than other. Floats made parrallel and adjusted to give a 38.5mm height when touching spring ball on needle valve.
Installed back on van, running better and fast idle now works properly when engine cold (suspect due to correct float height now). Engine will accelerate properly with small - medium throttle inputs, but sudden throttle inputs still cause popping/blowback through the carburettor. However Engine has stopped stalling when under heavy throttle. It will now backfire and then rev. I have two distributors, one a retard/advance unit and one just an advance unit. Tried both and no difference in running between the 2.
Headache problems! - Removing plugs from ignition control unit and putting together to set idle/mixture. Can get the engine settled at 900 rpm, and adjust mixture to minimize backfiring. However cannot seem to dial out of it, richer or leaner it gets worse. It can be minimized and is only noticable at quick/large throttle inputs. However if the engine is turned off, it will refuse to start untill the idle control unit is plugged back in. This causes the engine to now idle at 1.1k RPM, and will not drop down to 900. Also ignition timing is way out, with 1.1k RPM the reading is 20+ degrees BTDC. The backfiring gets significantly worse with the idle control unit plugged in.
Ignition timing - Without idle control unit, idle is 7-8 BTDC, and at revs without advance vacume goes to 28 BTDC which is good. With vac advance goes to 40 BTDC, once again good. However isssue is idle control unit has to be connected to start engine once warm, and then timing is 20+ BTDC at idle at 1.1k RPM.
The whole thing is begining to do my head in, as you adjust one thing and it knocks everything out and I cant be sure which settings are correct. I am also running out of things to adjust/check. Only two things left I can think of is to reset rocker tappet pressure as maybe valves not opening fully, and spray carb cleaner on carb when running to check for vacume leaks. However carb is in good condition so i doubt there will be a vac leak!
Soon the only solution will be to pay £250 for a dyno/set up session, but any pearls of wisdom would be greatly appreciated.
I am so damm close to having it run great but frustratingly it seems just out of reach!
