distributor cap

On a single distributor 308 , is it feasible to have a fault with the cap ie arcing which only effects one bank? Or a problem with the rotor which would only affect one bank? Any thoughts appreciated.

 

If the rotor does not spin true, I do not see why the problem could not exist.

But conversely, as a Super-Mech here pointed out to me awhile back, the older F-Car caps and rotors have ALOT of slop in them so .......... maybe not.

Do you have a hair-line fracture in the cap perhaps-- and I mean one VERY TOUGH to see even with darn GOOD light?

 

Yes its possible that there is a crack that I can't see. Not a cheap item to replace (!) so was trying to make sure first.

As the car revs higher the spark to the near bank is breaking down and car starts backfiring. Have changed everything else (coil,coil lead , condenser,ballast resistor) so thinking it must be cap or rotor. Dizzy has been rebuilt also.

 

(If you mean the stock single distributor) Yes, because it has the "two level" rotor with two business ends 180 deg apart -- each end serves one bank. Do the rotor ends and cap internal contacts at least look reasonable? If you are running points, have you confirmed that the (electrical) dwell of each point is reasonable?

 

Yes all looks in reasonable condition and it is the single stock dizzy. I did not realise that each end of the rotor did a different bank and this is (I think) a likely cause but misfire is intermittant, although currently it is permanent thus helping some diagnosis.

The points correctly were set when the distributor was rebuilt .

 

Understood, but sometimes things go wrong later (even if only shortly later) -- something shifts, or a contact pad pits or breaks off, etc.. It's an easy (no disassembly req'd) measurement , and something that you can measure at low and high RPM to see if it is different (i.e., if the dwell goes to 0 deg at high RPM, the corresponding coil will not fire).