Thanks! This is specifically the information I was looking for. Unfortunately your picture didn't come out (I'm on a Sun workstation), but I have a pretty good idea of where I should tap a vacuum ho
Just went out and took a good look at exactly where I drilled the hole. It took me two tries to get it right. The spot is at 11:00 on the front throat, and goes through the bore only a few thousanth
Can anyone explain to me why my '74 Midget with SU's has a simple vacuum advance fitting right on top of the intake manifold and yet so much care and attention is being taken to locate the vacuum pic
I don't understand... If the vacuum advance on my '74 Midget works with manifold vacuum, why won't manifold vacuum work with other configurations?? Richard '74 Midget '68 MGBGT '58 Morris Minor
Manifold vacuum decreases as your throttle plate opens. The dizzy wants full advance at full throttle. if you use carb vacuum,the dizzy gets an appropriate indication of the engines running demands o
Just walked in to this discussion. Does all this mean that I should re-plumb the vacuum on my '72 1275 with SUs? My vacuum also runs off the manifold. Is tehre a way to take it off the carbs? chuck
Chuck, I'm not sure. I was just answering the question of why most cars don't run manifold vacuum to their dizzy. I'llsend you the dissertation I just sent richard on the hows & whys Mark Haynes
No bother, You've just made me have to think, that's all. It's not the volume of vacuum (i.e.how many cc's of air pulled through per unit time) but the differential in pressure relative to ambient. b
Thanks for checking. So I guess I want to keep the hole as close to the top (90 degrees from the throttle shaft) as possible. Drilling this hole is making kind of nervous, since you have to drill fr
You might have the vacuum hooked up to the wrong location. On the 'stock SU carb/manifold' setup that cam on my 1275, one of the SU's had a nipple on one side specifically for the vacuum advance. Th
Are you sure it's a vacuum advance fitting on "top" of the intake manifold and not part of the smog equipment. Vacuum advance is generally taken where the quickest reaction to throttle movement is.
Actually, the correct place on the SU for the vacuum advance is a throttle vacuum port on the carb. If you are drawing manifold vacuum you have the hose hooked up in the wrong place. On the SU, the
I can't tell you the exact size. I'm trying to remember where I got the vacuum nipple from. I think I pulled it carefully out of an old SU, and drilled the hole as close to the same size as that nip
In confused. Just went out and looked CAREFULLY at my SUs on my stock '72 1275. The vacuum comes off a nipple just about in the center of the intake manifold. There are NO unused nipples on either (o
The age of the carbs I looked at is unknown, although they are late smog SUs with the little spring & pin in the butterfly. I thought 69-74 had these, but I guess I was wrong. Just be thankfull you
sent this to Richard, then read your post. I now am joining you in the confused arena, as up until now I thought I knew what I was talking about, now, humbly am not so sure. The original reply was h
I know I'm opening a 'new can of worms' (again), but what did you do about your PVC, and crankcase breathing with your webber set up?? I"m trying to get everything up and running first, and I figure
Chuck The earlier SUs have a nipple on the front carb near the throttle shaft. Later carbs used the intake thus a different timing mark becuase the intake advanced the dizzy right from start up. Not