Misfiring on acceleration

Hi everyone, I've recently replaced the manifolds on my series 3 lightweight and had the carb cleaned and rebuilt. After putting everything back on I found that the engine would idle nicely but misfire and sometimes stall on acceleration. I was told that this could be a leak somewhere around the inlet manifold/carb area so I took it all apart again and replaced all the gaskets and sealed them with silicone gasket stuff etc, which has improved things a bit, but the problem is still there.

Also it starts really quickly from cold but after a few seconds slows down and eventually dies, sometimes even with the choke fully out. This only usually happens the first time and then it starts fine, but misfires on acceleration.

So, basically I think I can eliminate the air leak thing. Just wondering what the other possibilities are? I'm going to check the spark plug gaps but I'm pretty sure they're ok. As for the rest of the ignition related stuff I'm a bit in the dark.

Any help would be much appreciated,
Cheers.

when refastening manifolds did you leave 4 x bolts holding then together loose so that they can align themselves ,float level,dirt in carb,if fitting new plugs fit whole lot cap ,arm,condenser,leads, coil

Yeah the manifolds were together for at least a day or two before I put them on properly. As for the rest it sounds like it could be an ignition thing so I'll have to start looking into that. Should be interesting...
Cheers mate.

not sure if ou misunderstood but normally you slacken 4 bolts so manifolds can move in relation to each other when tightening to head

I had exact same problem, turned out to be a bad spark plug, but because they were almost new took me ages to work out that was the issue, like you ended up rebuilding the carb, but as already said, your going to just have to work your way through the ignition system, take the plugs out and look at the colour of them see if there is one thats noticably blacker than the others, have a look at your points check for burning or pitting also check the gap, condensers can also cause major problems, best to replace with a lucas one if possible, could even be a bad lead, is your lightweight 24volt?

Sounds either too rich and soiling plugs - have you emission tester? Or basic ignition problem. When was ig system replaced leads, coil etc?

I see what you mean Jamesmartin, admittedly I didn't do that. Thanks for explaning what you meant. Can't face going near the manifolds again just yet so I'll bear that in mind for later and hope it's not a problem... cheers.

I don't know when any of the ignition stuff was last replaced (except spark plugs) and to be fair a lot of the bits look pretty old so maybe I should start replacing them.
It's very likely the mixture is too rich because I've been messing around with the mixture a lot to try and get it running properly. Haven't got an emissions tester but might not be a bad idea.

Interesting what webbedfoot says because the spark plugs were the first thing I replaced so I've pretty much chalked them off as finished with. Might have to look back into that. I guess I'll start checking the leads and distributor etc and see what happens. Electrical stuff is not really my strong point. Could be interesting...

Thanks everyone, sorry for the late reply.