It's been a while. A couple months back I took the head off my C1200 as the headgasket had been oozing (since I've owned it). Gave the valves a mild lapping and had the head shaved a tiny bit as there was a corrosion mark where the gasket leak was. At the same time I had the carby professionally rebuilt.
Anyway, put it all back together and it ran like total rubbish. Some vacuum leak, back firing, rough, blowing smoke, the whole lot. Plugs were black very rapidly.
Pulled it apart again, sealed the manifolds, carby, redid the valve gaps (25") still runs like bollocks. Timing is perfect. New cap, condensor, points.
Just compression tested it, 130 on every cylinder.
I've pretty much done everything except pull the pushrods and see if I bent one and re do the valve gaps for the 3rd time..
Also can you get replacement lifters? Does anyone know the part number?
Setting the clearances can be tricky....its easy to get 050 gaps.....there is only a very small spot on the cam lobe where its correct.......But except for a bit of clatter,doesnt make the engine run bad,.........does your engine still have the steel rings to align the inlet manifold?....its easy to crush them into the head.....a worn distributor will cause rough running,as will fouled plugs.Dont use radio supressed plugs or leads either ,the cap will carbon track......Lifter p/n 888451R1
2 mistakes I made when doing up an Inter ABD 240 motor and had similar issues
Used a modern coil which puts out around 40,000 volts....bought coil to suit FE Holden or similar which puts out around 13000 volts
Fitted electric fuel pump which had too higher pressure....went back to mechanical lift pump [from Auto Surplus] in Melbourne
Fixed the problem for me. Hope this helps
Plugs getting black very quickly sounds like over rich carby. Perhaps float level too high, especially if a bit of crap has got in there and it won't quite shut off. Your carby should be a Stromberg, yes?
They don't usually cause any trouble. (unlike their predecessor the Holley 2110)
Are the plugs sooty, or wet? Also, do you have any old ones you can put in? Fouled plugs can cause really crap running all by themselves. Does it blow black smoke? Have you been able to get it running at least well enough for a quick spin?
John's suggestion, too can cause vacuum leaks if things aren't aligned right. You can't always hear them, need to spray them while running and see if revs change.
It will be worth it. With properly lapped valves, it should run like a top. One mistake I have made is not getting everything quite as clean as I thought I had - got crap in the valves. Turning the engine by hand with the manifolds off, I could hear leaking valves.
All the best, please let us know how you go.
My wife said I never listen to her..., or something like that....
I had a bit of Stromberg trouble ,not an Inter but a XA Falcon......the thing wouldnt idle ,had to be run at 1000revs,overheated like crazy in traffic,would screech the wheels when the auto was put into drive,but would boil with the tranny in gear in traffic.......last straw was it started belching black smoke,opened the hood,and petrol everywhere ,dripping off the motor........carby was flooding ,and wouldnt stop......on went a 2V head and a Holley......but never had any trouble with them on Inters,ever.