Misfires at 3500 rpm

[elan4me]

I have finished the restoration my 69 S4, from chassic up. We rebuilt the engine including the stromberg carbs (but not the jets). It runs fine at low rpms and lower gears. But in 4th gear from 3400 rpm and up it runs rough. I have gone back through the archives to look for help, but I now don't where to start. Any suggestions?
Stan

[gjz30075]

Is your ignition system in top shape, ie, new coil, wire, plugs, points, cap, rotor, etc?

Greg Z
'72 Sprint

[steveww]

If you are in the UK you are welcome to PM me and I would be happy to have a chat and go through all the required set up. Over the last couple of years I have learnt a lot about Stromberg carbs and the Lotus twinc. I also have aquired quite a bit of reference material as these carbs.

PS If you are in the US you can also contact me it's just that the chat might be difficult because of the time difference and the federal set up is not so familiar to me.

[elan4me]

Thanks for the help. I am in the US. It has all new ignition system except for the coil. That was maybe my next step.
In the archives there was quite a bit of discussion about too much fuel pressure. How do you check it?
Stan

[steveww]

A fuel pressure meter is the only way to check the fuel pressure. Using a Filter King is always a good idea. Is the car running the regular mechanical fuel pump or an electrical one? Most electrical fuel pumps give more pressure than the needle valves in the carbs can cope with.

If you are sure about the ignition system then it is time to check the carbs. How old are the needles and jets? Take a close look at the diaphram, make sure it is in tip top condition. When were the carbs last rebuild? Are they fully balenced for flow and mixture? Any air leaks?

If you go through all the settings methodically then the engine will run sweetly.