Thread: Rotating distributor

Originally Posted by Scallops

The carby cover and body where the needle and valve sit are attached by 3 bolts (2 on the upside and 1 facing down at the rear) with spring washers - these are fine. Float action was checked to make sure float actually floats and has no small holes.

Intake manifold gasket is as new - was replaced when I got her only a matter on a year or so ago - it's all good.

Don't have a vacuum gauge. But I feel the issue is simply in the mix ratio and the timing - it's fully retarded, as set by forum member. This is a well known culprit for carby backfires, is it not?

Hi Scallops

I am not sure if you picked up on what I wrote, about the thickness of the washer between the needle and seat valve and the carby cover.
If a thicker washer is installed there, the end of the valve is then further down into the float chamber and that means the fuel level is being kept at a lower position, the carby then feeds a leaner mix of charge into the intake manifold.

As the amount of fuel is fed by the venturi effect is controlled by the float level, any increase in that level means that more fuel is drawn into the charge mix.
Likewise any decrease in the float level means it has a a leaner charge mix.

So measure the level of the fuel in the carby and see if it is at the correct height.

Once set the mixture doesn't change suddenly, it will take years of work to wear out the throttle plate shaft, to the point that the air leaking past the shaft causes lean mixture problems.

If it has suddenly started to run lean, I would be looking for a blockage, in a fuel filter, a jet or some water down inside the carburetor.

As with the timing of the distributor, once set the body of the distributor should not be disturbed, as the timing was correct for that particular motor.

Any problems again that occur over a relatively short period are due to a problem that can only happen quickly, the points are the first thing that I would look at here and the reason for this is that any variation in the points gap can have a immediate effect on the timing.
If the heal of the points has worn and the points close up the timing is retarded, as the points open later and for a shorter time (see references to dwell angle).
Likewise if the points have burnt quickly from say a trip were the motor was fast running for a long time , and the gap has opened, the timing has advanced.
If the points are burning too fast during normal use, I would be replacing the condenser as well.

Now the ticklish question

and the timing - it's fully retarded, as set by forum member. This is a well known culprit for carby backfires, is it not?

It is a chicken and the egg situation, which comes first?
Basically if the mixture is corrected, only the timing issue is left, to put back to the original timing setting.

The article below is a good explanation of what does happen


Cheers Arthur

Ref: Why does retarded timing = hot engine? - SmokStak
01-04-2010, 03:00 PM
Andrew Mackey
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Re: Why does retarded timing = hot engine?
When the engine fires normally, the fire burns completely (or nearly so) within the combustion chamber. The heat is kept within the combustion chamber, and as the pressure drops during the power stroke, the superheated gasses cool. As the power stroke occurs, the cylinder absorbs the heat, and when the exhaust valve opens, the burned cool mixture is blown out of the cylinder and combustion chamber.

When timing is retarded, peak pressure and heat is delayed, and is not confined to the combustion chamber. Delayed ignition causes the peak heat and pressure to occur in the cylinder body itself. The flame actually burns the lubricating oil off the cylinder walls, causing more friction. As the combusting mixture is not under high compression, it is less dense, again causing further delays in the burn. When the exhaust valve opens, extremely hot, still burning gasses are blown out the exhaust port. past the valve. This flame heats the valve red hot, and superheats the head and manifold. Running an engine retarded for any length of time, under load, will cause valve burn out, and excess wear to the rings, piston, and cylinder.

Running a 2 stroke engine retarded can have severe consequences as well. Again, it allows the main flame and pressure to build within the cylinder instead of the combustion chamber. The excess heat in the cylinder burns off the lubricating oil, overheats and distorts the cylinder body, and when the exhaust port opens, allows direct flame impingement on the face of the port and piston surface to occur. A severely retarded 2 stroke, under load will melt the piston and damage the exhaust port in short order! I have seen engines with the pistons actually blow molten aluminum out the exhaust port, to the point that the rings also get burned off by the flow of burning exhaust out the ports.

An engine, with no load, running retarded may not give symptoms of retarded overheating until it is too late, and damage has been done. This may show up as burned head gaskets, warped or burned valves, poor ring seal, and severe power loss, especially when loaded for a length of time. With the piston removed, a sure sign of retarded timing is a brownish or blued cylinder wall, and a severely varnished, or galled piston skirt. This is directly the result of an over heated piston, and the fact that oil has been burned off the cylinder.

Ignition Timing is not the only reason for retarded timing! Setting the mixture too lean, and or an intake leak (worn throttle shaft, leaking gaskets, broken hoses) will also cause heating due to the lower density of fuel to air within the cylinder. The lower fuel/air density causes the mixture to burn longer, with a similar result in damage.

Andrew

Originally Posted by Scallops

The carby cover and body where the needle and valve sit are attached by 3 bolts (2 on the upside and 1 facing down at the rear) with spring washers - these are fine. Float action was checked to make sure float actually floats and has no small holes.

Intake manifold gasket is as new - was replaced when I got her only a matter on a year or so ago - it's all good.

Don't have a vacuum gauge. But I feel the issue is simply in the mix ratio and the timing - it's fully retarded, as set by forum member. This is a well known culprit for carby backfires, is it not?

Most of us S1 owners are Dan Following this with interest though.

Perry

Arthur - yes, sorry - the needle is a new unit with the correct washer. Confident the fuel is at the right level here.

As for the timing being fully retarded - I don't know why Dave left it like that either....but I'm sure hear-in lies the problem...

Appreciate the efforts to help gentlemen, but it's a bit like me trying to explain to someone how to deconvolve a seismic field record. Too many factors if one party doesn't speak the language. Time to pull the wallet out and get it done properly.

If you want to PM me your phone number I will ring you and we can go over the timing, Yes there are a number of things that have to be about right but they are not that hard to tune, with a bit of practise you can normally get them running pretty good even with very worn parts.
Dennis

Originally Posted by Scallops

Arthur - yes, sorry - the needle is a new unit with the correct washer. Confident the fuel is at the right level here..

Hi Dan

Good! that confirms that. if the mixture was still wrong, I would be looking now for an air leak somewhere between the carby and inside the head.

As for the timing being fully retarded - I don't know why Dave left it like that either....but I'm sure hear-in lies the problem.....

If you haven't moved the body of the distributor yet and only adjusted the octane selector, it's time we did the ignition thing and for these old motors, static timing is the only way to go. See below for another article, this one is about a rover car motor, but it does it the old way and which has the correct settings for the Land Rover's motor as well.

Appreciate the efforts to help gentlemen, but it's a bit like me trying to explain to someone how to deconvolve a seismic field record. Too many factors if one party doesn't speak the language. Time to pull the wallet out and get it done properly.

The only thing my wallets good for, is cutting leather gaskets from! , leave yours in your pocket.

Language barriers are a problem, when a mentally burnt out, dairy farmer, from across the water in Tasmania, tries to communicate with a banana whisperer from across the Northern boarders, using something as antiquated as this sped up version of Morse code!


The Rover P4 95/110 Owner's Manual

Distributor maintenance
Every 6,000 miles (10.000 km), remove the distributor cap and lubricate as follows:
1. Lightly smear the cam with clean engine oil.
2. Lift off the rotor and add a few drops of thin machine oil to lubricate the cam bearing and distributor shaft; push the rotor on as far as possible.
3. Place a drop of clean engine oil on the contact breaker lever pivot, taking care not to oil the contacts.
4. Add a few drops of thin machine oil through the contact breaker base plate, to lubricate the automatic timing control.
Distributor Occasionally clean the distributor as follows
1. Wipe the inside and outside of the cap with a soft, dry cloth; ensure that the small carbon brush works freely in its holder.
2. Slacken the nut on the terminal block and lift off the spring and moving contact, Ensure that the contacts are free from grease or oil; if they are burned or blackened, clean with a fine carborundum stone or very fine emery cloth and wipe with a petrol-moistened cloth. Replace the moving contact.
3. Every 6,000 miles (10.000 km) check and adjust the contact breaker clearance as follows
(i) Remove the distributor cap and turn over the engine by hand until the contacts are fully open.
(ii) The clearance should be .014 to .016 in. (0,35 to 0,40 mm). The feeler gauge should be a sliding fit between the contacts.
(iii) If necessary, slacken the two screws which secure the adjustable contact and adjust by means of the adjuster screw until the clearance is correct; re-tighten the two retaining screws.
(iv) Replace the distributor cap.

Ignition timing
In addition to automatic timing advance and retard mechanism, the distributor incorporates a hand setting control, known as the octane selector. This is a vernier adjustment attached to the distributor, fitted with a sliding portion controlled by an adjusting screw and a calibrated scale marked R (retard) and A (advance) with a number of divisions between. The standard setting for the ignition is with the long line of the scale on the sliding portion against the mark on the selector body, thus leaving one division further possible advance and four divisions retard.
This setting is correct for premium fuel (80 octane) and with a clean engine, but should pinking develop as a result of the need for decarbonising, the control can be retarded a little by turning the screw in a clockwise direction. Do not forget to return it to the original position after decarbonising.
In certain countries very low grade fuel is supplied, in which case it may be necessary to adjust the octane selector to avoid pinking, even with a clean engine.

Ignition timing
Should the distributor have been disturbed, the ignition timing must be reset as follows:
1. Set the contact breaker point gap .014 to .016 in. (0,35 to 0,40 mm) with the points fully open.
2. Rotate the engine in the running direction until the mark on the flywheel, as detailed below, is in line with the pointer, with both valves on No. 1 cylinder closed.
95 and 110 models (6cyl motors) -6°'s mark when using premium fuel. Should be 15° for early 4 Cylinder 1.6 Litre and 10° for the later spread bore 2 Litre Land Rover motor using 80 octane petrol.
3. The distributor rotor will now correspond with No. 1 cylinder high tension lead terminal.
4. Set the octane selector so that the fourth line from the left-hand side of the calibrated slide is against the face of the distributor body casting.
5. Slacken the pinch bolt at the base of the distributor head; rotate the distributor bodily in the opposite direction to the arrow on the rotor arm until the contact breaker points are just opening with the fibre cam follower on the leading side of the cam; re-tighten the pinch bolt.

Cheers Arthur

Just because you have a new washer under the needle/seat.. doesn't mean the float level is set correctly .. this gadget I made is the only way of determining where the float is . http://www.aulro.com/afvb/showthread.php't=116045 The petrol should be 5/8" below the top edge . As Arthur explained , it will stuff up your mixture if it isn't correct. You must do this test with the carby sitting level..no good if it's tilting , it's best to remove it for the test.

You use an old main jet holder and drill it out .... you have to also drill the internal pathway in the jet holder as well otherwise the petrol won't feed trhough ther jet holder . Took me ages to realise the float level is critical on these things.

Another thing is: drill out the main air bleed jet if you have the small one fitted . It sits on top of the emulsion tower ..easy to see it. It helps enormously to do this , to run a non-rich mixture as these buggers tend to do run rich if they are worn.

BTW now you will understand why so many owners in the UK install a NOS Weber and chuck the old Solex in the bin

Mike

Originally Posted by wrinklearthur

Hi Scallops

We'll keep going along with the lean mixture theme, Is there any chance that two washers, or too thick a washer was fitted between the carby cover and the body of the needle valve and seat, as this would cause the float level to be too low?

How good is the intake manifold surface and its gasket?
Also have you inspected the intake manifold for any corrosion holes or stress cracks, that may have developed?
Can you fit a vacuum gauge, to do a run and tell us what the results are?

Cheers Arthur

The Series 1 Solex has a bad habit, from overtightening, of distorting the mounting flange (2 bolts). Sometimes it will produce quite a nice whistle. Put a sheet of medium wet & dry on a very flat surface (an old LR door window is ideal), & rub the carby flange around (not in one direction) a couple of times. You will soon see if the surface is flat or bowed. If flat leave alone, if not keep going until flat. This method also works on the less often distorted top cover. Wash thoroughly afterwards, don't want to ingest grinding powder. In general diecast (zinc alloys) age over time & naturally distort to some extent.

The motor running okay with mixture enrichment open suggests the problem is neither lack of fuel getting into the float chamber nor is it a timing problem.

I have had a partly blocked jet give this symptom, but I cant remember which one. The good thing about the solex is that they are easy to get out to check.