Ignition timing.

Steve C

Member
HI, my car has been running a bit rough lately, i have only basic knowledge on the car ( p6 3500 auto) checked and cleaned the plugs, carb mixture, checked the points, and ignition timing, ive found that if the timing is set to 6 btdc the car is sluggish with not much go at all, however with playing about with the timing it runs a lot smoother, and seems to run a lot better in all respects, having got it running better, i put the strobe light on and noticed the pointer was now about 1/4 inch past the 10 degree mark, not sure how the car seems to run so much better with the timing so far out, could this cause damage!!, any advice would be great.
Many thanks Steve
 
Mine ticks over at 14 BTDC and likes it, but it isn't standard, or anywhere near close.

You could check that

1/. TDC is accurately measured on your pointer, they are often a long way out

2/. Check your vacuum is working on your distributor
 
Many thanks for the reply, the vacuum seems to be working as it should, as for the pointer being accurate, i have no idea at all, but as it appears so far out, its a possibility.
 
To check the pointer is accurate line it up at say 6 degrees and move the points till they are just opening and lock them there. Then start the engine and check it with the light. It should read somewhere near the same depending on how close you got it static. If not its moved...

oh, and disconnect the vacuum advance first...
 
oh, and disconnect the vacuum advance first...

Hi Mike,

You don't actually have to do that if the engine is running the twin SU carburettors as that arrangement uses ported vacuum. What that implies is there is no vacuum advance provided at idle. Engines that run manifold vacuum do receive vacuum advance at idle, and on these engines it needs disconnecting.

The vacuum advance on the Rover only works on light throttle openings when cruising along a motorway or something similar. When driving around town, or using throttle to accelerate etc, there is no vacuum advance provided.

Ron.
 
Your quite right Ron, I normally disconnect it anyway as it cuts down on the possible error sources. For example: If the idle is too high or the engine has been setup to idle on just that carb there can be just enough vacuum to add a degree or two. I suspect this particular patient may have a siezed or inoperative mechanical advance as most Rover distributors only give 26 -28 degrees max advance and 14 is halfway there...However he does need to check his timing marks are correct before he starts pulling the dizzy to bits.
 
The std timing on many engines is conservative, and can be usefully advanced , within some limits. The acid test is if it doesnt ping('pink?') under load advance it a bit more.The higher the octane used, the more resistant to pinging it should be. Early MX5s respond well to advancing 4degrees with no harmful effects.
The centrifugal advance provided by the dizzy is an ADDITION to the static advance - Des Hammil's book has some useful info on max advances for the various version of the V8.
 
Does anyone have an informed opinion about timing a P6 V8 by sound? I time mine with a light at 6 degrees TDC, but, notice that the engine will achieve higher rpm if the distributor is adjusted slightly off of that standard mark. I would suspect that in a 50 year old car the timing chain has stretched, and, that this could account for the variation. I've often wondered if the car would run better if timed "by ear" instead. I am by no means a mechanic, so, I am appreciative of any thoughts on the subject.
Thanks,
Drew
 
Hi Drew,

It is possible to set timing by ear. You listen for an increase in engine revs which will cease when when you advance beyond optimum. Of course you also need to test for pinging. Road testing will reveal if your initial timing is ok or too much, then it is a matter of trial and error.
The standard Morse timing chains don't remain 'as new' for long, typically requiring replacement after only a few years.

Ron.
 
Hi Drew,

It is possible to set timing by ear. You listen for an increase in engine revs which will cease when when you advance beyond optimum. Of course you also need to test for pinging. Road testing will reveal if your initial timing is ok or too much, then it is a matter of trial and error.
The standard Morse timing chains don't remain 'as new' for long, typically requiring replacement after only a few years.

Ron.
Hi Drew,

It is possible to set timing by ear. You listen for an increase in engine revs which will cease when when you advance beyond optimum. Of course you also need to test for pinging. Road testing will reveal if your initial timing is ok or too much, then it is a matter of trial and error.
The standard Morse timing chains don't remain 'as new' for long, typically requiring replacement after only a few years.

Ron.
Much appreciated, Ron. It seems "common-sensical", but, I know that often doesn't stand true with these old cars. Again, thank you. Drew
 
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