Oscillating Distributor Cap

[Dave81]

Gents,

Whilst going through the car to stop an oil leak I pulled the distributor (was the base gasket). Decided to put on a new rotor and cap to try and sort some of my running issues.

Did all this put it back together....no more leaks....yay!

What I did notice is that the cap now looks like its slightly oscillating with the rotor movement. The cap and rotor is an Airtex premium jobbie from Rockauto and is listed for the 318. it seems to fit fine bar the hold down clamps don't seem as tight on the new cap as the old........this seems to be leading to slight movement when the cap is locked down.....hence movement when rotor spinning.

Also noticed that I seem to be getting an electrical whirring noise at the same time???

It hasn't solved the issue of the car sounding like its running on 7 when cold (seems okay when up to temp). It didn't run rich this time (my eyes were happy) but the idle speed is still down and near stall (low rpm cold and warm - not at charging level).

The car was running and revving happy apart from the slight oscillation at the cap.

Cap is my main Q:

Secondary Q: Is the running on 7 (unbalanced feel through the car when cold):
New Plugs, Leads, Cap, Rotor, entire charging circuit, VR and EIM.

Any ideas on what to look at. Could sticking valves be the issue???

Help.........

Only thing old is the Coil (forgot to get one)............

[Dave-R]

The cap needs to be clamped down tight and there should be a tang to stop it rotating at all so that needs to be a good fit.

I would also check that the distributor bearings are not shot and that the distributor shaft is straight. I had a car once where the shaft was bent slightly and it was hard to spot.

Use some logic. What is making the cap move? It shouldn't be touched by anything.

The rotor might be hitting one plug terminal. Hence the movement of the cap and one cylinder not firing.

[Charger]

but the idle speed is still down and near stall (low rpm cold and warm - not at charging level)

I still think that’s down to the weather, my car idles slightly slower in winter too, if your car was set up in the summer (I remember you had some work done for MOT??), I would just leave it

Is the running on 7 (unbalanced feel through the car when cold)

are you sure it’s only running on 7?? or just running Bananarama! cos it’s cold, these are not like modern cars, again my car takes a little more coaxing when it’s 0deg than when it’s 20deg

are you still warming the car on your drive or going for a run??

[Dave81]

The cap needs to be clamped down tight and there should be a tang to stop it rotating at all so that needs to be a good fit.

I would also check that the distributor bearings are not shot and that the distributor shaft is straight. I had a car once where the shaft was bent slightly and it was hard to spot.

Use some logic. What is making the cap move? It shouldn't be touched by anything.

The rotor might be hitting one plug terminal. Hence the movement of the cap and one cylinder not firing.

The old cap didn't move at all...... Both Caps are identical height (checked that before install). Possibly a height difference in the rotor, but cant see it. The old cap was clamped real tight (had to use a screwdriver to prise the away. The new one was a case of just pushing a little to get it to sit and bite.....Think I will pull the Cap and investigate!

The running on 7 was present on the old Cap, Leads, Plugs and rotor! Think the cold weather and lower idle is just exaggerating the problem!

[Dave81]

but the idle speed is still down and near stall (low rpm cold and warm - not at charging level)

I still think that’s down to the weather, my car idles slightly slower in winter too, if your car was set up in the summer (I remember you had some work done for MOT??), I would just leave it

Correct Si....Was working fine when the temps were in the teens.

Is the running on 7 (unbalanced feel through the car when cold)

are you sure it’s only running on 7?? or just running Bananarama! cos it’s cold, these are not like modern cars, again my car takes a little more coaxing when it’s 0deg than when it’s 20deg

are you still warming the car on your drive or going for a run??

The engine is not happy, sounds like its missing and moving quite a bit too on its mounts (out of balance almost). Up to temp it settles as does the movement. It also sounds like its back on 8. Could be crap running, but I've seen cold start issues when you have to feather etc.......this just seems a bit more than that.

Wonder if its worth investing in a laser temp gauge and taking readings from the individual exhaust port outlets. If its missing id expect a lower reading on one???

Warming the car in the garage (with doors open to maintain life). Rear is on axle stands at the mo, so not driving this side of my its next garage visit.

The exhaust is blowing at the manifold (passenger side), have a few holes along the length on both sides too. Not sure if this would affect the running?

Will be getting a whole new system in Spring to go on!

[Dave81]

Double post...

[Charger]

but the idle speed is still down and near stall (low rpm cold and warm - not at charging level)

I still think that’s down to the weather, my car idles slightly slower in winter too, if your car was set up in the summer (I remember you had some work done for MOT??), I would just leave it

Correct Si....Was working fine when the temps were in the teens.

Is the running on 7 (unbalanced feel through the car when cold)

are you sure it’s only running on 7?? or just running Bananarama! cos it’s cold, these are not like modern cars, again my car takes a little more coaxing when it’s 0deg than when it’s 20deg

are you still warming the car on your drive or going for a run??

The engine is not happy, sounds like its missing and moving quite a bit too on its mounts (out of balance almost). Up to temp it settles as does the movement. It also sounds like its back on 8. Could be crap running, but I've seen cold start issues when you have to feather etc.......this just seems a bit more than that.

Wonder if its worth investing in a laser temp gauge and taking readings from the individual exhaust port outlets. If its missing id expect a lower reading on one???

Warming the car in the garage (with doors open to maintain life). Rear is on axle stands at the mo, so not driving this side of my its next garage visit.

The exhaust is blowing at the manifold (passenger side), have a few holes along the length on both sides too. Not sure if this would affect the running?

Will be getting a whole new system in Spring to go on!

if that’s the case then I think you would be wise to leave well alone

I think you are looking for problems that really aren’t there, just our crap cold damp winter weather

unless you intend to use the car regularly in winter

would be a bummer to upset something now then find out it’s not running right next spring

warming the car in the garage isn’t the best IMO

2 schools of thought when laying up a car for the winter
• don’t bother running it at all
• start it every week for 10 mins and pootle up and down the drive

I’m in the don’t bother camp, ‘start it every week for 10 mins and pootle up and down the drive’ can do more harm than good, could foul the plugs, fill the exhaust with water not evaporated off properly, etc, etc

next dry day take it out for a hoon, I think you’ll find it’ll be fine when it gets warmed up proper

[MilesnMiles]

I'm with Charger on this. Run regularly or leave alone.
As for dizzy cap, my truck had the same issue. Visibly moved about and yet ran and started like a top. I changed dizzys between cars and no difference, just a badly fitting dizzy cap that still worked

[Dave81]

I still think that’s down to the weather, my car idles slightly slower in winter too, if your car was set up in the summer (I remember you had some work done for MOT??), I would just leave it

Correct Si....Was working fine when the temps were in the teens.

are you sure it’s only running on 7?? or just running Bananarama! cos it’s cold, these are not like modern cars, again my car takes a little more coaxing when it’s 0deg than when it’s 20deg

are you still warming the car on your drive or going for a run??

The engine is not happy, sounds like its missing and moving quite a bit too on its mounts (out of balance almost). Up to temp it settles as does the movement. It also sounds like its back on 8. Could be crap running, but I've seen cold start issues when you have to feather etc.......this just seems a bit more than that.

Wonder if its worth investing in a laser temp gauge and taking readings from the individual exhaust port outlets. If its missing id expect a lower reading on one???

Warming the car in the garage (with doors open to maintain life). Rear is on axle stands at the mo, so not driving this side of my its next garage visit.

The exhaust is blowing at the manifold (passenger side), have a few holes along the length on both sides too. Not sure if this would affect the running?

Will be getting a whole new system in Spring to go on!

if that’s the case then I think you would be wise to leave well alone

I think you are looking for problems that really aren’t there, just our crap cold damp winter weather

unless you intend to use the car regularly in winter

would be a bummer to upset something now then find out it’s not running right next spring

warming the car in the garage isn’t the best IMO

2 schools of thought when laying up a car for the winter
• don’t bother running it at all
• start it every week for 10 mins and pootle up and down the drive

I’m in the don’t bother camp, ‘start it every week for 10 mins and pootle up and down the drive’ can do more harm than good, could foul the plugs, fill the exhaust with water not evaporated off properly, etc, etc

next dry day take it out for a hoon, I think you’ll find it’ll be fine when it gets warmed up proper

Sounds like a plan.......may try and get it out over Xmas for a run. If not will leave until Spring then try and break it.........

[Dave81]

I'm with Charger on this. Run regularly or leave alone.
As for dizzy cap, my truck had the same issue. Visibly moved about and yet ran and started like a top. I changed dizzys between cars and no difference, just a badly fitting dizzy cap that still worked

Gotta love old cars!

[drewcrane]

Does the dizzy shaft move at all,can you wiggle it back and forth with the cap off?

[Dave999]

if i fit a slant 6 cap to my hemi 6 dizzy i get the same problem

look the same size but the slant 6 cap wibbles about

wrong or crap cap
cap on backwards
wrong or crap rotor

jammed or bent and jammed king lead contact


Dave

[Dave-R]

The other problem with running the engine in our cold damp winters is you get condensation in the engine that contaminates the oil.

Went out in my Corvette a few times last week. Noticed a build up of brown sludge in the inside of the oil filler cap. That does not happen all summer long no matter how wet it is. But combined with the cold there will be moisture forming all over the inside of the engine.

[MilesnMiles]

Yes Dave, my truck had that especially as it was parked on the drive and often used for short runs. I thought it was head gasket at first, but it wasn't and it went away in summer.

[Dave81]

Does the dizzy shaft move at all,can you wiggle it back and forth with the cap off?

No the distributor itself is rock sock solid in the hole. Its rotating with the motion of the rotor. The cap that came of sat evenly and there was no play.
The new one even before clipping down doesn't seem to seat properly, almost like it has a raised ridge......I'll go and dig around this weekend!!

It has no affect on the running.......I just don't like it and want it static!