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1993 Range Rover LWB
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21 Posts
Discussion Starter #1
I adjusted the timing on my 4.2 RRC to Rave specs at idle with no issues. I'm a newbie to timing and have a question: with the vacuum line unplugged, if I increase the throttle to higher rpms, shouldn't the timing advance due to the mechanical advance in the distributor? With the vacuum line unhooked, my timing barely moved (no more than a degree or two at higher RPMs.) Is this normal? Do I have an issue with the springs/weights in my distributor?

Thanks much.
 

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1970-1995 Range Rover Classic
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286 Posts
There are so many factors to consider here - attempting to responding on a basic level.

To answer your question regarding 'normal' - the answer is possibly.

The vacuum advance exist to allow the mechanical distributor to 'keep up' as throttle is applied.

If everything is OEM - the springs and advance are properly functioning (as new) - you may see 2-4 degrees of advance change with the vacuum disconnected: 12-16 degrees of advance at 2500 -3000 RPMS.

However, with the vacuum advance connected you should see 22-24 degrees of advance - this is loosely considered 'total time' - if you only ran at WOT it would be total time and the vacuum advance would not be needed.

Once you change the CAM and modify the fuel/air ratio - you may choose to customize the spring and advance rates of the distributor to a specific RPM to align with a CAM - not many options available, sadly.

Again - all high level stuff - lots of internet info to read.

Only responding to assist - best of luck!
 

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1993 Range Rover LWB
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Discussion Starter #3
There are so many factors to consider here - attempting to responding on a basic level.

To answer your question regarding 'normal' - the answer is possibly.

The vacuum advance exist to allow the mechanical distributor to 'keep up' as throttle is applied.

If everything is OEM - the springs and advance are properly functioning (as new) - you may see 2-4 degrees of advance change with the vacuum disconnected: 12-16 degrees of advance at 2500 -3000 RPMS.

However, with the vacuum advance connected you should see 22-24 degrees of advance - this is loosely considered 'total time' - if you only ran at WOT it would be total time and the vacuum advance would not be needed.

Once you change the CAM and modify the fuel/air ratio - you may choose to customize the spring and advance rates of the distributor to a specific RPM to align with a CAM - not many options available, sadly.

Again - all high level stuff - lots of internet info to read.

Only responding to assist - best of luck!
Thanks, that is helpful. The part I'm focused on is the 2-4 degrees with the vacuum disconnected. I'm not getting any movement at higher RPMs...possible time to service the distributor.
 

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1989 Range Rover Classic
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356 Posts
It's possible the weights/springs have broken free or there is another internal issue, as you should definitely see advance without the vacuum line at higher RPM. Max advance for a RRC is roughly around 3000-3300, so between idle and that RPM you should definitely see it rise at least 10-12 degrees if not more. I believe total timing without vacuum is ~24 degrees (though I'd need to verify) and closer to 28 with the vacuum line (at no load). Powerspark in the UK sells a drop in replacement distributor that works pretty well, and is pretty fairly priced. Losing out on that much advance is a significant cut to your higher end HP, we're talking a loss of as much as 30%, so it's well worth looking into.
 

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As LanceL posted, you should be seeing advance from the weights as you increase rpm when the vacuum is disconnected. Usually aggregated it would be plus 14 degree for this part but you'd normally have to be above 3000rpm to see it at full movement.

Quick check in distributor, remove cap then gently turn the rotor with your fingers anti clockwise. It should move against spring pressure (this the springs on the mech) and spring back to home when let go.

Sometimes when a rotor is changed by pulling it off it can dislodge the advance retard components, the above check is to see if that is still in place. It should move smoothly and return without catching anywhere.
 

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1993 Range Rover LWB
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21 Posts
Discussion Starter #6
As LanceL posted, you should be seeing advance from the weights as you increase rpm when the vacuum is disconnected. Usually aggregated it would be plus 14 degree for this part but you'd normally have to be above 3000rpm to see it at full movement.

Quick check in distributor, remove cap then gently turn the rotor with your fingers anti clockwise. It should move against spring pressure (this the springs on the mech) and spring back to home when let go.

Sometimes when a rotor is changed by pulling it off it can dislodge the advance retard components, the above check is to see if that is still in place. It should move smoothly and return without catching anywhere.
Thanks for the thoughts. I was able to turn the rotor counterclockwise about 5 degrees or so and then it sprung back, so that seems normal. Did a timing test again, no vacuum, up to about 2500rpm. Timing is actually retarding ~1-2 degrees rather than advancing at higher rpms. With vacuum on, all seems well. Assume some issue with weight/springs?
 

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Something odd here. That doesn't sound bad, the 5 degree approximately, as it would need 7 on the rotor to effectively have 14 total (crankshaft is moving twice as fast as distributor shaft) to be correct.

You can't turn the rotor the full amount without excessive force, but the bob weights will action this ok from their mechanical advantage. So likely to be total of 7 degrees of rotor shaft movement.

So it seems correct, but the report (observations of timing movement) would suggest otherwise. As it's set ok static and runs ok, I'd suspect something in the measuring method, but can't immediately think what that would be.
 

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At this age (of the car) and with likely unknown history you should really remove, clean and 'overhaul' any suspect part. I might sound a bit scary (and you can mess it up), but I suggest you remove the distributor and take it apart. It is likely gummed up and as said possibly springs detached etc. If the springs are gone/unclipped the weight are just running against the housing giving 0 advance, but allowing the shaft to turn. I have opened a few that are exactly like that - weight wearing a groove inside the housing.

To remove, turn engine to TDC, MARK the orientation of the distributor (distr-block), MARK location of the rotor before and after removal - it rotates slightly dt the skewed gear. Remove bolt and pull out. You obviously have a timing gun so you should be able to reset easily.

There are descriptions on disassembly online. It all comes apart and goes back together mechanically.

On a positive note it is a fairly easy (and cheap) repair and will make a HUGE difference in power and fuel consumption.
 

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1993 Range Rover LWB
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Discussion Starter #10
At this age (of the car) and with likely unknown history you should really remove, clean and 'overhaul' any suspect part. I might sound a bit scary (and you can mess it up), but I suggest you remove the distributor and take it apart. It is likely gummed up and as said possibly springs detached etc. If the springs are gone/unclipped the weight are just running against the housing giving 0 advance, but allowing the shaft to turn. I have opened a few that are exactly like that - weight wearing a groove inside the housing.

To remove, turn engine to TDC, MARK the orientation of the distributor (distr-block), MARK location of the rotor before and after removal - it rotates slightly dt the skewed gear. Remove bolt and pull out. You obviously have a timing gun so you should be able to reset easily.

There are descriptions on disassembly online. It all comes apart and goes back together mechanically.

On a positive note it is a fairly easy (and cheap) repair and will make a HUGE difference in power and fuel consumption.
Well I did it, and was pretty surprised to find that the springs were mounted to the wrong posts, in such a way that the weights were fully "extended" as if the dizzy was spinning at full speed, meaning no further mechanical advance was possible. Put it all back together, re-adjusted timing at idle, and now am getting correct advance without the vacuum under throttle. Last person to reassemble put the springs back incorrectly... thanks to all for your help.
 

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Nice work Flatbed, and less daunting once you commit to getting something apart too.

At least you've now got the right outcome.

Good advice from JS5D and one of the nice aspects of this forum that things can be talked through calmly to bring out ideas.
 
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