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Discussion Starter #1
Our 90RRC now has a new distributor (but her timing isn't happy. Installed 6* B (as Rave instructs, vac off etc.) and then wanna strobe time her to 9*/10* B but she dies. A tooth either way doesn't help. Also tried dizzy installs starting at 10* al the way to 18* - She seems to like the 6*B best as she idles there. Don't think her timing chain is bad as the rotor moves with the slightest hand crank. Anyone have a different method? Thanks.
 

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There is a way to check of the timeing chain is loose on you tube
I would think a 91 if the chain hadn’t
Been changed in the past
It is due
With that said
Try setting the time by feel
And sound
But if it’s loose
It is a battle to set timeing
 

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Discussion Starter #3
Her rotor moves with the slightest hand crank both back and forth. If the chain had slack then her rotor would probably hesitate before moving. Thinking her chain is snug.
 

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Is there a reason for using more base advance timing setting? As you found they run ok at 6degree std spec so unsure of the need to go with a variation in my experience.

I can see with a strobe on mine (160,000 miles) some flutter/staggering on timing marks, so evidently the chain on mine is not in its prime! But set to 6degree maximum with vac tube off then accepting the error as below that is fine.

If you run more initial advance it then seems to me to cause ongoing offsets for base idle setting and subsequent running issues that chase through the system in setting up which are unwanted.

Mine will run at 6degree setting with perfect idle, plus run out with no issues on wide open throttle all the way to maximum revs absolutely no issues at all. It has good clean burn too, with very low emmisions figures. Fuel consumption seems to be high end of range too with aggregate figure of 19.7 mpg for UK gallon measure.

Curios as to origins of advice to run with ignition in advance of std, and what it's trying to achieve.
 

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I suggest you also check that the TDC on the crank pulley is in fact TDC (top dead center). The pulley is rubber mounted and can slip or be slightly inaccurate. There are various techniques available online to check TDC. Also plug the vacuum line you pull off as leaving it open will introduce air into the manifold and affect the engine running at idle.

The idea behind advancing is that to get maximum engine efficiency the pressure of the explosion needs to occur at the right time after top dead centre. Too early and the force is lost as the piston is not advancing down enough, too late and you lose pressure through the starting exhaust stroke. Since the explosion (flame front - chemical reaction) occurs at constant speed (and is dependent on pressure and mixture) while the engine can run at high or low rpm, so you need to bring the start of the explosion forward as the speed of the engine increase in order to have the maximum force at the same correct moment after top dead center. In addition at low load the flame moves slower so you require further advancing. Therefor the timeing of the engine needs to be variable and is constantly changing depending on speed and load.

For idle the ideal timing for efficiency is actually about 18 deg BTDC (Before Top Dead Centre), but this will give high NOx emissions so it is dialled back to about 8-10 BTDC (using ported vacuum rather than straight intake vacuum). Efficiency at Idle is not all that relevant as fuel consumption is low in any case. Correct timing is more relevant when you are actually driving which most of the time is at part throttle. For normal cruizing at about 3000 rpm at low load advance can be as much as 45 deg BTDC. The mechanical advance is achieved with the bob-weights, while the load advance is achieved with the vacuum, which is applied on top of the bob weight advance (low load it high vacuum is additional advance).

Retarding your ignition timing (less BTDC numbers) will reduce engine efficiency and cause the engine to run hotter. Advancing it too much (larger BTDC numbers) will cause pre-ignition which is damaging. Typically allowing for fuel qualities etc engine timeing is set on the conservative side (slightly retarded).

For the Rover V8 timing convention the thinking is in fact not around the idle settings since this is not all that relevant, but instead as follows: around 28deg at 3000 rpm without vacuum advance (vacuum line plugged!). So this means you use the mechanical (speed) advance of your distributor to achieve the 28 deg, then back at idle you should get about 8-10 deg (if not your mechanical advance is wrong or broken). Then you reconnect the vacuum, since it is most likely ported, it will not advance your timing at idle, but will do so at some load when the throttle blade has passed to vacuum port. If you want to check your vacuum advance, apply a vacuum through a hand pump and it should advance about 15 deg (total advance at low load and high RPM is thus 28+15= 43 deg)

All of the above is incorporated in a proper running engine. I would start with checking your timing is correct, then check the distributor is working correctly (weights and vacuum) they can seize or be just plain wrong application for the car. With a timing light and a hand vac pump you should be able to check the correct operation.

Enjoy!
 

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Thanks JS5D I like discussions like that, and do understand the impact it has on combustion.

But it's more that why you'd need to advance it from factory spec at base setting that I'm getting at. If you isolate the vac on mine and turn distributor while running it just brings the idle up progressively going above 6degree before, making the base idle set procedure not close out.

If you do that, then you just end up with offsets in setup of base rpm and compromised IACV activity as I see it. Questions about which are often brought up on here. It seems that the manual spec of timing is prerequisite to decent hot and cold idle performance without compromised behaviour from that view, which is obviously desirable.

I don't feel it needs more advance in total as there is enough in the distributor to work without any obvious compromises. I've run modified 3.5 size to 7000rpm on std timing with no real limits on performance, I know it's not a particularly fast burn combustion chamber but it doesn't seem to need anymore advance to run well.

Hence I don't see any quantified data to advise advance greater than std on a stock setup.
 

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Thanks JS5D I like discussions like that, and do understand the impact it has on combustion.

But it's more that why you'd need to advance it from factory spec at base setting that I'm getting at. If you isolate the vac on mine and turn distributor while running it just brings the idle up progressively going above 6degree before, making the base idle set procedure not close out.

If you do that, then you just end up with offsets in setup of base rpm and compromised IACV activity as I see it. Questions about which are often brought up on here. It seems that the manual spec of timing is prerequisite to decent hot and cold idle performance without compromised behaviour from that view, which is obviously desirable.

I don't feel it needs more advance in total as there is enough in the distributor to work without any obvious compromises. I've run modified 3.5 size to 7000rpm on std timing with no real limits on performance, I know it's not a particularly fast burn combustion chamber but it doesn't seem to need anymore advance to run well.

Hence I don't see any quantified data to advise advance greater than std on a stock setup.
Hi RRLondon,

Since I have the pleasure of adjusting timing electronically to whatever I want, I took the time to understand (reverse engineer) the timing requirements for the Rover V8.

Turns out, after a bunch of trails and errors that there is very little you can improve upon from the base mechanical/vac distributor and really there is no reason at all to deviate from stock settings. No big surprise since Land Rover would have done that. I have not really been able to increase efficiency much at all by advancing the timing. The Rover V8 is an ancient design which seems just 'very' fuel inefficient. Changing the timing a little does not have much impact on either power or efficiently I find, so running it safe (not too advanced) is what I ended up with.

The only area's where you are a little stuck with the mechanical distributor are:

1) The Mechanical/Vacuum advance is a little slow in reacting and can cause pinging at sudden acceleration (not a big deal). Electronic control is just wonderfully smooth
2) There is some inaccuracy, especially as wear progresses, however with basic maintenance (oil change, checks etc) it should never got that bad.
3) At idle the timing is kept static 'dumb' with a balance between torque, efficiency and emission. On electronic systems the idle timing can be varied constantly to keep the rpm steady with different loads and temperatures etc. This allows much more advance idle timing (less torque) which will result in lower temperatures, without stalling as the timing retards as required. A Cooler running 1984 Range Rover with AC at full blast is GOOD in Houston Texas!
 

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Another consideration is the cam you are running. With the 9.35:1 engine, we used to swap out the standard high compression low lift cam for the standard low compression (8.25/8.13/8.5:1) high lift cam (new lifters, chain, etc at the same time, oh and end bolt as they are different) and then set the timing up at 12 degrees BTDC dynamic at idle.

It made a huge difference to the trucks (RR and 110) in terms of power and fuel efficiency, without losing any of the drivability and it is still all standard parts. For a further improvement, fit an early distributor with some form of modern electronic ignition fitted. You will need to alter the oil pump drive, but it is a very easy job, 15 minutes at the most.

The LC cam part number is ERC2003, probably superseded now, but still available from Rimmer on ERC2003A as an after market.
 
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