MGB: rough idle issue

my midget started acting a bit strange lately. it seems that even after warming up the engine idle's pretty rough. i recently removed my engine, so maybe i moved something or a setting when removing or reinstalling. anyways. the car seems like it's missing or something similiar.

1275 with dual su's.

after warm up it feels like it is taking in too much air or bogging down... you can hear a burble when you push the accelerator. it clears if you push it hard... but im not racing. in addition at lights it idles really rough. almost dies. seems like it's misfiring, because the engine vibration reminds me of when i had a bad timing issue in my mustang. it's an electronic ignition so i have only tuned it by ear. i am going to re adjust it again tomorrow (i havent messed with the dist. since the reinstall.. but didnt remove it so it doesnt seem like that would be the issue).

anyways... im just trying to get some more advice on what i should check.

tomorrow Im going to look at: the dist. and carbs (although i didnt mess with these either) the only thing i have messed with was the choke cable. i am also going to switch dist. cap, plugs and wires tomorrow (since I have them sitting around and have never installed them).

thanks for any and all advice in advance.

dkm

Hey DKM, the first thing I would check is that the carb pistons freely move up and down (gotta remove the air cleaners and lift the pistons and let them drop), make sure the carb dashpots have oil, and check that all the carb linkages are doing what they're supposed to.

Others will certainly chime in with other good suggestions, but these are what I would look at first. Good luck with it.

-DKM (the other DKM)

I'm sure you've checked, but forgive me if I suggest the obvious:
Check for vacuum leaks. Improperly fitting or tightened inlet manifold for instance. How about the vacuum advance to the distributor? If you are still running it, check the hose and make sure it is tight on the manifold and the dizzy. ( just pushes on but should be snug. ) Ensure any unused ports on the inlet manifold are plugged ( ie: the one for the vacuum advance if it has been dispensed with, or the crankcase ventilation system port if the pcv system has been dispensed with)

Before messing with the carbs, it would be wise to check the above as leaks will affect mixture especially at idle. Getting the carbs properly set will be impossible if there is a vacuum leak.
It would also be a good idea to have a manual to follow if you have never done SU's before. They are not complicated, just "fiddly", and bear no resemblance in procedure to any other carburetor in so far s getting them set properly is concerned. Mixture is the easy part, there is a LOT more to having those carbs synchronized and functioning properly. Again, not complicated, but fussy and fiddly with things needing to be done in a particular order to get 'em right.[/i][/b] Familiarity or a manual are [i][b]essential IMHO.

Good luck

Could be a leak, might have had dirt in the bowl that is now in the jets from removing . Fix , take apart and clean, blow out the jets.
Will

Dave,
Like everyone has advised, check for any vacuum leaks. My '73 was acting exactly like yours. The problem turned out to be worn throttle (butterfly) shafts. They did not seal properly and caused air leaks. Plus, they were worn enough so that I think the butterfly would sometimes hang up slightly in the bore. These things both contributed to all of the issues you have described. Now my car runs great after just replacing the shafts. I was going to have the carb bodies bushed for the new shafts, but decided not to do that (even though I bought the bushings) since the carb bodies were not not worn enough to justify the machine shop expense (+$250) needed to ream and press the bushings.
Jack