MGC Intermediate" MISS "on my 69 MGC roadster

[jeffreys]

Intermediate" MISS "on my 69 MGC roadster

I have a great running MGC at idle and on acceleration.The problem is that it has a nasty miss from 1500 rpm's up.It still has a good amount of power but if you listen to the engine running over 1500 rpm's it misses terribly.I have no vaccum leaks ,adjusted valves,new plugs,cap,wires,rotor,rebuilt carbs,pertronix ignition ,timing is ok and has good compression,It is most annoying pllllllllllease help.Any suggestions would be greatly appreciated.Thanks,Jeff

 

[DrEntropy]

Re: Intermediate" MISS "on my 69 MGC roadster

Which carbs? And is the dizzy advance working?

 

[jeffreys]

Re: Intermediate" MISS "on my 69 MGC roadster

I put a timing light on the engine and increased the throttle and the timing did advance.I also put a vaccum on the distributor with a hand vaccum pump and the advance assembly moved (engine off).The carbs are the original SU's HS6.Which were just rebuilt by a major SU rebuilder.Thanks Jeff

 

[MGZT260]

Re: Intermediate" MISS "on my 69 MGC roadster

But do you have vacuum at the hose connecting to advance mech while running? It takes a combination of both advances to have a smooth operation. You may have determinind only that the vacuum advance is working correct. The centrifugal adbvance is teh one most likely to freeze up or encounter broken springs, etc if vacuum system is otherwise fine.

 

[JPSmit]

Re: Intermediate" MISS "on my 69 MGC roadster

have you looked at the plugs after running awhile? I had a miss in mid range - turned out I was running too rich and they were carboned up

 

[Bob Claffie]

Re: Intermediate" MISS "on my 69 MGC roadster

If you are running "non-wire" wires, (carbon impregnated non metallic cores) with a dizzy cap that has the old style screw in connectors occasionally they will degrade at the connection point and arc causing a random miss. Bob