Common tuning problem.

[Kilroy]

Hey guys.
Pardon me - but I am going to be a little circumspect with this.
Being from New Zealand, I grew up around British vehicles. That is why I still have them. We get many of our formative impressions in our youth.
I had British cars, and later got into British bikes. I still have one I bought new - 35 years ago. Bike that is.
Luckily for me - there were many people around then who knew the intricacies of such machines. They were happy to pass on what they knew if you approached them in a considerate manner - smart-asses generally got the bums rush.
There was a popular opinion in those days, that because the British Motor Industry was in crisis financially, that it followed that the machines they produced were not properly developed.
Many people who continue to tell me why my Marinas are so bad, seem to think they know how to fix them.
I have acquired a lot of Marinas which people have 'fixed'.
Frankly - its all crap. The people in the factory did know how to make them go best. They tried everything that anyone else has tried, to see if there was something to gain from it.
If it was not adopted, you can be sure that there was a problem with it.
Bikes, cars - it was all the same.
Maybe I am lucky that I was one who did listen to what the factory people said, and I still put my money on the fact that if you set your car/bike up the way the manual says, it will perform best.

So.
In the early days with Marinas, I had a lot of trouble getting the ignition timing correct. There was the fact that just as I did begin my Marina habit - we lost lead from petrol, and that introduced a few issues.
Also. Because the Marina was not very well thought of, a lot of the examples that came my way were quite neglected from a maintenance perspective. People had given up on them simply because of what others said.
I adopted a number of workarounds for the timing issue. Mostly, I set the timing by 'ear' rather than by the manual.
Until I made a discovery.
Subsequently, I found that around 50% of my Marinas had the same problem, and just tonight, I found another. That is why I am writing this.
I find it hard to believe that I could be the only one to have this problem. Maybe you do too.
It is to do with the vacuum advance in the distributor. This makes a vast difference to smooth running, acceleration, and ease of starting.
The problem has been the same on every car that had this issue, and it has been caused by previous owners.
I keep kicking myself when I find another - in that I was fooled yet again, and did not check, as it is very easy to do so.

In the distributor, the points are held in place by a single screw. You have to loosen it every time you adjust the points gap.
You also have to remove it entirely to replace the points.
This is probably where the problem begins.
Under the head of the screw, there should be a spring washer, and a flat washer.
If either are missing, you probably have the problem.
Without either of these washers, the screw will hit the rear plate which moves with the operation of the vacuum advance unit.
It then causes that plate to either lock totally, or fail to operate smoothly.
The reason I was having so much trouble with timing was because the vacuum advance unit was jammed, and thus it was impossible to set the timing correctly.
The cure is simplicity itself.
Replace the missing washer.!
Then set the timing exactly as the manual states. It works perfectly.
Perhaps the average owner in the UK is a bit more careful when it comes to such matters, but obviously over here, they are not.
A number of these cars had been taken to workshops for specific attention to tuning problems, and they had missed this altogether.

Check yours.
It makes all the difference in the world.

[MarinaCoupe]

Thanks Kilroy

Been there, done that, learnt the lesson, but had never thought to say it on here.

Good tip.







Chris
www.marinacoupe.co.uk

[MGBV8]

Here in the UK, the quality of fuel is not what it used to be. The cars were designed to run on fuel with a much higher octane rating for starters. In the UK we use the RON method of measuring octane ratings, as opposed to the RON2 method that most other countrys use.
Whilst an A series will run on practically anything, In the case of a B series IIRC something like 105RON octane was the "food" of choice back in the day. These days, outside of the pumps at race tracks where you can still get fuel rated at 102RON, the best you can realistically buy easily is 99RON known here at the pumps as "super unleaded" with 95RON known as "regular unleaded" and the most widely avaliable.
Also of pertinence to classic car user is that "super unleaded" has less bioethanol content which as we all know eats fuel lines and O rings in carburettors etc...

Whilst I would agree with you that the manual is a great *starting point* for tuning a car, I do not believe that it will arbitrarily give the *best* settings for timing - every engine is different after all not withstanding the inferior grade of fuel avaliable. To get as complete a burn of each inlet charge as possible, timing must be advanced as far as is possible until pinking just about starts to occur under load and then back off 1 degree.
To that end, the best way of optimising the timing is to set it up as per the book and then take the car on a series of road test with the timing progressively advanced slightly. At the point pinking can be detected under load we can determin that the threshold for that particular engine has been reached and we can then back off the timing one degree. Repeating the road test will confirm that there is no longer any detectable evidence of pinking.

Another factor is the choice of fuel that the individual owner intends to use. It is imperitive that the vehicle is setup on the fuel that is will be run on. From a personal point of view, I exclusively use Shell optimax in my vehicles which is rated at 99RON. So, I am able to run a fraction more advance than someone else who might exclusively use 95RON in their vehicle.

There's a lot to be said for using higher octane fuel in classic vehicles. Certainly, problems associated with run on can be negated. Similarly, there are slight MPG benefits to be had. The so called "superunleaded" fuels have some detergent properties which helps keep deposits on jets and in bloat bowls to a minimum and then of course, as mentioned previously, there is the benefit of lower bioethanol content.

Then of course there is the myth that supermarket fuel is somehow "inferior" to branded names. Well, the fuel all comes from the same source. It is not unusual to see Morrisons, Shell, Esso etc... tankers all quieing up at the same pump at the refinement plant. The difference between each "brand" is the variants in the additive package which is added to the fuel at the point of loading the tankers. Furthermore, each blend of additive package will be unique to each individual supplier.

Cheers,

Jon.

[jiversteve]

Here in the UK, the quality of fuel is not what it used to be. The cars were designed to run on fuel with a much higher octane rating for starters. In the UK we use the RON method of measuring octane ratings, as opposed to the RON2 method that most other countrys use.
etc....................................................

It's the little things as Kilroy says. I had a dizzy that was not performing right, turned out to be a leaking vacuum unit. Worth highlighting that they are not all the same and like the distributors internal springs and weights, are specific for each engine/car.

But the fuels are not what we had, the mechanical part are not all like new, and we are now spoilt by having modern emission controlled cars with sensors and ignition timing maps.

I am of the old school, check all the parts of the ignition system, set the timing by the book, and then road test and tweak the timing for performance and to avoid the dreaded pinking.

As a little aside, I doubt that many of us have looked critically at our camshafts, followers and rockers. Any wear on these can change the valve timing away from the design spec, causing a drop in performance.

[MarinaCoupe]

Jon

Good points well made. One thing though, my understanding was that the higher RON rated fuels were the ones containing ethanol rather than the lower RON fuels, with the ethanol helping to boost the RON rating.







Chris
www.marinacoupe.co.uk

[jiversteve]

If I remember my school chemistry lessons correctly, Ethanol does raise the RON value, making the fuel easier to self ignite but conversley contains about 2/3 the energy levels.
Now i will have to go back to my text books and do some reading.

[MGBV8]

Chris, that's not the case. Up until very recently Shell V power was classified as E0 standard (Ethanol free) across the board.
However, as of 2010 Shell begun blending ethanol with its V power fuel to E5 specification (5% Ethanol content) to comply with the legal obligations of the RTFO’. (Renewable Transport Fuel Obligation) which requires all transport fuel suppliers to ensure that, by 2010, 5% of their total aggregate fuel sales is made up of biofuels.
However, it's not quite that clear cut. If you choose to purchase 97/99RON fuel there is a good chance it will still be E0 standard, as fuel distribution logistics are a factor in whether or not any given fuel supplier is able to meet the RFTO requirements for a specific area without having to add Ethanol to it's high octane blends.
You can guarantee that the 95RON grade fuel sold in this country will be classed as an E5 fuel since it is the most commonly purchased petrol whereas the higher octane fuel represents a smaller segment of a distributors sales. To be RFTO compliant the volume seller will definately be rated at E5. It costs the distributor to add ethanol to the product and with higher octane fuels being less popular and more expensive to produce adding E5 accross the board would represent additional unneccesary cost that the accountants would no doubt find abhorrent.

In more recent history, it was intended to introduce E10 bioethanol blends into regular unleaded by 2013, however that proposal was kyboshed as it would mean retro-fitting an awful lot of modern vehicles to be compliant. The introduction of E10 has been shelved until 2015 when it is anticipated that many of the vehicles currently on the road will have come to the end of their natural life and will have been replaced with newer vehicles which are currently being built to be E10 or greater compliant.
As classic car owners we will clearly have to adapt. I believe Burlen (The parent company of SU carbs) have already developed the necessary upgrades for certain carburettors and suitable fuel hoses are freely available. The only remaining issue that is most pertinent to marina owners in particular is that eventually when E10 blends become a fact of life it will be necessary to have the fuel tanks appropriately lined. It may be necessary at this point for the club to commission new compliant tanks to be made.

As mentioned further up the page, Ethanol is indeed an octane booster - in fact an E10 blend will add 2 points to the RON rating of blend X. For what it's worth, Brazil has been using E20 blends since the 70's and found it necessary to make the following adaptations to cars:
- Changes to cylinder walls, cylinder heads, valves and valve seats.
- Changes to pistons, piston rings, intake manifolds and carburettors.
- Nickel plating of steel fuel lines and fuel tanks to prevent ethanol E20 corrosion.
- Higher flow rate fuel injectors to compensate for oxygenate qualities of ethanol.

There should be plenty of further bedtime material on both on FBHVC and FIVA's websites to digest if my post hasn't already bored everyone to death. My apologies to Kilroy for dragging the thread off in a bit of a tangent!

[MarinaCoupe]

Yes I have been following the FBHVC work and have written something up hopefully for the next club magazine.







Chris
www.marinacoupe.co.uk