I have been having some problems with inconsisent timing on my new motor.The distributor is a 57+ style that I purchased as a rebuilt unit last year.When I had the distributor out I did some checking on the existing freeplay of the shaft.The up and down not the sideways as its fine with new bushings.The clearance between the collar and lower body is at .050 and specs are .022-.036.I can fix that with a shim kit I just ordered made by Mr.Gasket.When I checked the upper what I call cam assembly there is another.047 freeplay.When I pulled it off there is no thrust washer-its missing.My question is does anyone know how much freeplay is supposed to be in that cam to shaft?The Ford parts book lists the thrust washer for a 59-61 292  distributor at .020.Seems to be the only one used with the y-block dizzy.That would still leave .027 freeplay.I have a washer on hand correct diameter but its .030 thick..How much freeplay  is really required for cam to shaft clearance?I did some research on the internet and too much vertical freeplay CAN affect the timing.Can also affect wear on the cam gear and the distributor gear because the mesh of the teeth is slightly off.When I reinstalled the original loadomatic just to check my theory,the timing marks stayed as set.Never varied from original set timing even when revved up and returned to idle.The distributor I am working on would return to different settings each time it was revved up and timing marks would "float".I had removed the Accel kit and reinstalled new points so it is not the problem here.I believe its  the excess play in the distributor shaft.

  

Mark:



I just checked a NOS 57 Ford distributor for clearances and found the shaft end play was .028” between collar and housing



The distance from bottom of flange that rests on engine block to the bottom of the gear (the flat area below the gear) is 4.984 with shaft pushed tight to the housing (without the .028” free play)



I do not think the free play in the cam to shaft clearance is critical as it is a vertical movement so should not affect the timing and your rotor spring will have a downward force to prevent it rising. The washer that is installed likely acts as a bearing point for smoothness of operation. You could use a wave washer to remove the free play. (edit) Just thinking on the wave washer as not a good idea s it could cause wear on that little spring retainer inside the rotor cam and your cam could jump off the advance weight pins.



The problem with excess free play in between the collar and housing with engine running is it can change the timing due to the distributor gear being helical cut and when rides upwards or downwards causes the rotor to rotate and change the timing set.



Usually the problem with the top bushing wear or excess end-play is caused by installing the o-ring found in the gasket kits between the flat of the distributor flange and engine block. This o-ring is used with the later distributors and is installed in the groove half way between the block flange and end of the housing. This causes the distributor to be riding upwards instead of the flat of the distributor drive gear riding on its bearing perch inside the block. The downward pull of the distributor shaft by the camshaft will cause top bushing wear and end result gives excess end play. I have also seen the rubber gasket that is used with crankcase vent tube used on the rear of the valley cover used under the distributor flange, same thing happens to the top bushing resulting ending in excess end play.

marv

Thanks Marv! I got the freeplay betwen the collar and body down to .026 using the shim kit from Mr.Gasket.Are you  saying the seal that came on this distributor should be removed?I know the original does not use one because there is no groove for it.If I remove it I wont get oil seeping up?I just added a thin washer for the cam assembly to ride on and its very close to the original ones thickness of .020.I have the body to gear measurement the same as the original loadomatic which I still have.NOW if I can find the little wire retainer clip for the cam assembly I wiill be all set.It popped off and I heard it land somewhere but so far havent located it.I tried some other retainers and nothing else will work so hopefully I can locate it.Dont have any extras.I will post the results as to wether this fixes my inconsistent timing problem,I believe it will as the loadomatic timing was dead on and didnt flicker at all when I checked it with the timing light.

  

If the distributor has the groove half way between the flange and collar and the o-ring is in the groove leave it there as it will slide down inside the distributor hole and the distributor when installed will be resting on the flange not the o-ring. The distributor must rest fully on the flat face of flange so the gear rests on the perch inside the engine and is not being held upwards by the o-ring or gasket.



If the distributor does not have that groove half way between the flange and collar don't put one under the flange as It will wear out the top bushing as said in previous post. The o-ring on those late style of distributors slid down the distributor hole. The early distributors just had an interference fit. It was not until the last y-block distributors that Ford used that o-ring as an oil seal so previously worked for many years.



When you clamp the distributor down it also gives less places to leak.

mavr

Hello Marv! I reassembled the distributor and got the freeplay down to .022 (recomended minimum clearance from shop manual)between the collar and the body.Put it back in and checked timing.STILL getting movement on the timing mark(not steady on the setting).I know something about this distributor is causing this to happen -but what is wrong with it?If I reinstall the loadadomatic timing doesn't move at all.Put this one back in and timing acts like there is a random miss.Put the light on other plug wires and its the same so its not just the #1 wire.How tight is the ignition rotor supposed to be on the upper shaft?I dont feel any movement of the rotor on the shaft but its not tight at all to remove from distributor.This one can be removed with no resistance at all and the rotor is  brand new.I know I am on the right track here because of the difference in the way each distributor works on the motor.The late model cap is fairly new  and I cant see anything obviously wrong with it although it does have the aluminum contacts and the loadomatic cap has the brass contacts which I prefer.I dont have an extra cap to try with.Any suggestions on what else I can check? 

  

The timing is not controlled by the cap or rotor.  It is controlled by the points or electronic pickup and the cam or reluctor.

John - "The Hoosier Hurricane"

Thanks John.I have already switched the electronic back to points.No better.I am just wondering if the rotor is shifting slightly on the shaft.Or is there possibly a problem with the cap?

  

Mark, your rotor can in no way affect your timing. It's only job is to send the spark to the correct plug. If you were to rotate the rotor and not the shaft after approximately 22.5 degrees the spark would be sent to the next or previous cylinder in the firing order but timing would not change. Cap is the same way. If made incorrectly it could cause the lead contact and the rotor to not be in alignment at the moment of spark but would not change timing.



Things that will change timing. Variation in camshaft, eliminated because you don't have a problem with your other distributor. vertical movement of dist shaft, you fixed this. Side to side movement of dist shaft, This is the most common cause I see. Side to side or rotational movement of the breaker (or advance if you prefer) plate, also very common. I would think this is where you should concentrate your efforts. If possible try to lock your breaker plate in one position, sometimes a small wedge or wood or plastic between the plate and the side of the dist body will do the trick. With the plate locked check your timing, if now good you have found the problem you will then just have to locate the cause of the looseness. Hope this helps, Mike

1956 Fairlane Victoria (ORREO)

 

Overlooking Beautiful Rimrock AZ

Mark,

           UNHOOK the vacuum line and block the hose. The other possibility would be that the wrong springs were installed and are not holding the weights in at idle. That system is located under the points plate. As John said the cap is not the issue unless you can SEE it move when it's running. The only way that can happen is for the rotor to hit it. You'd hear that!

Frank/Rebop

Bristol, In ( by Elkhart) 

Thanks guys.Going to have another look at it this morning.Its a rebuilt unit.Bushings are new with no side play.Vacuum line is off.As far as cap and rotor it was a thought is all.Different cap and rotor on the loadomatic.I have the plugs gapped wider than specs so I will pull them and reset.Maybe thet are misfiring because of the gap.Let you know what happens.