Engine misfires under load revving etc worst while driving of course. With the intake off found what seems to be excessive play between oil pump shaft and distributor with all the components in i can walk oil pump gear up and down. the brass bushing looks and feels new compared to one just purchased. Could this be more gear related/ or possibly something with oil shaft connection at pump. should the shaft gear be free to walk up cam gear like that? this is my 1st big block any info would be helpful thanks happy holidays all.
a few things.... with the distributer out... stick a big screw driver in the slot in the top of the drive gear....twist back and forth.. while observing it.. DOES IT ROCK or move side to side???? showing that the upper shaft is worn or the bushing is worn to one side... 2 decades ago .. i opened a new name brand oil pump drive for a small block... the shaft had been shot blasted... there was no polished bearing area... just really rough surface to rub against the brass bushing. ever play rock paper scissors ? guess who wins on that one.. that will actually allow the gear to get off center... taking the bottom of the distributer shaft with it.. ruining the distributer bushings... if the top of the distributer shaft shifts when you wiggle it.. you will have inconsistant clearances between the reluctor and the pickup coil...since you will have the distributer cap off.. can you look inside it.. can you examine the pattern of burn marks on the internal cap terminals.. see if the burn mark is evenly spread across the surface of the terminal.... |---| if its all to one side.. -|- | then the reluctor is on backwards.. there are 2 slots for the reluctor to line up on.. one for big blocks that rotate in one direction. the other for small blocks that rotate in the other direction.. get it wrong and the rotor will be pointing out into the air at high RPMs.. can can cause spark scatter... if the spark burn marks are on the inside TOP of the cap terminals.. then change your rotor.. somebody put it together backward.. square side out.. not round side.. leaves the spark too big a gap to jump... makes for really weird misfiring issues...i would also like you to spend 6 bucks at the local parts store on this Help/15 in. Universal Ground Strap Part Number: 60213 Alternate Part Number: 644-125this goes between the back of the heads and the mounting bolt on the ignition module.. it allows the high voltage spark traveling through the ground side to make a complete circle from the module through the coil .. then the spark plug wires spark plugs heads and back to the module base where the module is grounded...lastly if the reluctor is RUSTY.. or somebody has spray cleaned it.. sand blasted it .. change it.. if you own a digital volt meter... set it to 2K ohms... measure the resistance of the pick up coil... 500 to 1500 OHMs is expected.. usually around 980 ohms is what you find... thats good.. before you disconnect it... flip the meter over to your 2 volt AC or 20 volt AC scale...spin the shaft... you need to see really close or just over 1.0 volts AC for the ignition module to work properly... if it passes the resistance test... but does not create high enough AC voltage check the gap with that brass feeler gauge blade in your feeler gauge set.. 0.008 to 0.010" test again.. if it fails.. replace the reluctor.. they do wear out.. they do fail... they cost under 10 bucks at most parts stores... rust will ruin them.. sand blasting ruins them...
wait.. you did not say if you have chrysler electronic ignition.. or points.. or some other brand of distributer..if you have points... are they clean... is the condenser clamp tight.. is there a proper tiny ground strap from the breaker plate hold down screw to the hold down screw on the points.. so the points get a proper ground...when the points are closed... and the ignition switch is on.. the circuit through the primary windings of the coil is complete and its creating an electro magnetic field...as the shaft turns and the points open.. the current flowing in from the ground is disconnected. this causes the magnetic field in the primary side of the coil to collapse through the secondary windings creating a high voltage spark in the secondary windings.. if the points are burned or out of adjustment.. you will have spark issues.. perhaps scatter as the contacts are making intermittent contact.. could also have points bounce..
additional Thoughts...if you have the timing set to far advanced... too much compression.. too lean a mixture.. incorrect for your application mechanical advance curve or vacuum advance curve and limits... anything that causes PINGING.. detonation.. preignition.. you can get spark scatter as the crank is being hammered and it travels through the crank the wrong way.. through the timing chain and to the cam where it will stop and start as the timing chain slack moves from one side to the other...slack timing chain will also cause this... this is probably why some race motors have gone to Gear drive to avoid spark timing issues a improperly tuned harmonic damper could also cause this.. as the harmonic damper absorbs and dissipates the Torsion oscillation created by the compression stroke attempting to slow down that rod journal then the power stroke pushing the rod journal down..