Hi all, I have a 2L type 4 engine on twin 40 idf's, it currently uses a vacuum advance dizzy without the vacuum pipe connected ( because I don't have an outlet of off my carbs) It runs and starts fine, it pulls really well in all gears and generally feels pretty nice to drive. But when the revs get higher it feels like it has more to offer but not much more happens. So I'm thinking it must be because the dizzy because isn't advancing the faster it's goes, so I get me a second hand bosch 009, and it ran so badly I did t really consider it to be drivable, flat spots galore didn't accelerate in any gear as it should, some popping and backfiring, and it wasn't even too happy starting. Could it of been a duff dizzy? Anyway I took it off and am now back on my vacuum advance with no vacuum pipe connected and I'm back where I'm started. So what do I do next??? I know I'm not going to break the sound barrier in it, but I do want the engine to give me what it's capable of. So any ideas at all would be spot on. Cheers Austin
I don't think the vac advance will help with high rev acceleration. The exhaust may be too restrictive? Air correction jets too small/big? Weak valve springs?
Hi guys, cheers for the suggestions, paradox, don't I need to come of the carb for an advance? Zed, hi mate, cheers for the ideas, exhaust has got me thinking, it's a home brew item from the standard item but without the cat. No idea about the other 2 points tho bud.
Are you sure those IDF’s don’t have a vacuum advance port? Each carb should have a brass tube (blocked with a screw) for the distributor; shown on the drawing here: http://www.redlineweber.com/html/Tech/idf_adjustment_controls.htm. As Zed says it won’t help top end power when the vacuum is low but at least the distributor will work properly - and will be far better than a 009. Don’t drill the manifold, that’s okay for the brake servo but no good for the vacuum advance.
I would get the vac advance working just because it will at least rule that out. It sounds like a breathing restriction pretty much as @zed has said - a rolling road session to set up the carbs might be a wise investment.
Is the mechanical advance working? You need to get the vac advance working too. I had a problem with flat spots and lean mixture just off idle and it was fixed with a bit of messing with jets and emulsion tubes.
Who fitted the carbs? If you did, did you get them tuned on a rolling road? Twin carbs aren't something you can just bung on and expect them to be set up exactly right!! The stock dizzy is an SVDA... single vacuum, dual advance... the dual part relates to the fact that it is mechanical as well as vacuum... While the vac helps at low rpm, and other situations, the mechanical does the main advancement. Also when was the van last serviced?
