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MG TD TF 1500 - Lead additives in fuel

After being dissasembled and out of service for twelve years my TD is driveable. What is the consensus of this group on fuel additives?
E ARNOLD

Use them if it makes you feel more confident, but it's a pain in the a**. If you push the engine hard a lot, hardened valve seats are a good idea. Then you won't need additives at all. Valve seat recession is the main concern with unleaded, but reports of problems are rare. You probably won't need to use anything. Just check your valve clearances regularly, and adjust if needed. If you drive hard and find your valves tightening up a lot, pull the head and have a good machinist do the work.

I couldn't tell if you knew any of this from your post, pardon me if I oversimplified. I wouldn't worry about unleaded gas, wouldn't use ethanol blends if I had a choice at the pump.
Tom

Hi,
Re fuel additives.I have just had to switch from LRP(Lead Replacement Petrol)to Unleaded Fuel for our TF.No modifications have been done to the head or motor in any way.The car has run perfectly since the fuel changeover with a possible exception that the running motor temperature has increased 2 or 3 degrees.The boys in UK are saying that the temperature can be brought back to par by advancing the spark 4 degrees at 850 tickover.In Aust.,the Premium Unleaded BP FUEL is rated at 98 Octane.(you can also get Standard Unleaded at 92 Octane)Which is
better to keep the motor cooler? Any comments?
Cheers.
Rob.G.
Rob.Grantham

Dont worry too much about adding stuff to your tank. I pulled the head after about 20k miles useing lead subsitute stuff and found that it realy crapped up the plugs and left a lot of build up in the combustion area. Its hard to judge what your doing on a partial fill up , you have to kinda wing how much you dump in.
After a few years of just useing hi-test ( do they say that any more?) I pulled the head again and could not see any sign of undue ware. I do not beat the snot out of the car every time I go out but I do wip it up now and then just to see how it feels at 65 mph.
Most of the time I drive at 45 or 50. to me its not how fast I get there but what fun it is to drive it.
Alan

Rob, normally you would have to retard the ignition a few degrees when you use unleaded fuel. I don't know the octanerating of your LRP but assume that it might have been 98. Now even if you use Premiun Unleaded 98 octane in theory you may still have to retard the ignition because lead being a good anti knock additive will make unleaded fuel of comparable rating will have more tendency for the engine to pink. Now you don't seem sure about the temperature and I cannot confirm that it may have risen either but I would suggest that you adjust the timing to the point where under heavy load at about 2000rpm you can just hear pinking. When you reach that point it is just about optimum so leave it at that.
Iain MacKintosh

I suggest not getting too cocky with this one!

While my head has stainless inserts, many like your's don't. I put in lots of miles in a summer, and I can drive hard on occasion. It gives me peace of mind to know that I'm not likely to have a problem.

About 3 years ago, I got a call from a gal with a TF who was complaining of "losing power". She used the car regularly in the summer to commute 20 miles to her work, mostly on the super-slab.

Sure enough, her valve seats were shot. A direct result of NOT KNOWING not to use un-leaded fuel, or to add additive. Unlike the UK or OZ, we no longer have the choice to opt for leaded or LRP.

I would suggest you first do a compression test before touching the engine, whether its in or out of the car. Then decide, if the results are poor, the answer is obvious. Contrarily, you may have to do some valve work. Actually, inserting new seats is about a $100 job for head-work alone.

Or, you have to decide how much lead additive you'll use over nn years to off-set head-work costs. In Canada, we pay about $4 per can that's good for 2 T-Series tank-fulls. If you don't drive more than say, 2,000 miles per year, then use additive, but do compression checks at the beginning of each driving season, and maybe again during the summer - and log it.

You can also do some math - a TD/TF tank holds 14½ US gallons. At 25 mpg, that gives you (approx.) 360 miles per tank. Using Canadian Loonies (getting awfully close to the US buck, these days), add $2 for additive and this comes out to about 55¢/100 miles. 2,000 miles per season = about $11. In 9 years you would/will have paid for the inserts! (But by then, gas may be just too costly to justify out precious gems!)

On the issue of methanol, be careful with this too. All early English cars are not set up for it, and seals with any derivative of rubber, like the o-rings (Viton, I believe) on the T-Series valve stems, will simply get eaten-away. Ditto carb seals, seals in the tank around the sender, etc.

Iain

98 octane gas fuel here is dreadfully dear. I think most TD/TF-ers use 92 which already contains some anti-pinking additives..

As for static advance, again one has to be careful here, because many of us have switched to the pertronix solid state system, and static advance (retard) is not too clear cut - at least according to my quick search of the archives, so to categorically apply a retard of a few degrees may not be necessary. In my own case. I found that the TDC setting is OK, and I’ve yet to hear any pinking.

Gord Clark
Rockburn, Qué.
Gordon A. Clark

Agreed Gord that static advance is out with Pertronix, I use Lumenition Magnetronic which is much the same. The centrifucal curve will of course remain the same and I like to hear just marginal pinking on heavy load indicating that my engine is optimally tuned.

This valve recession thing is another matter. All cars are different and are affected by mileage, driving styles etc. It is therefore very difficult to advise. For me however if I had a head off I would always advise that hard inserts be installed on the exhaust seats then you ar of course free to use unleaded and hopefully quickly recoup the costs of the additives.
Iain MacKintosh

RobG:-
"In Aust.,the Premium Unleaded BP FUEL is rated at 98 Octane.(you can also get Standard Unleaded at 92 Octane)Which is
better to keep the motor cooler? Any comments?"

My 1500 likes Shell Optimax PULP (not the new super-Optimax with Ethanol).

On normal ULP I get a bit of run-on when its warm, but don't get this problem when running Optimax.

One would assume this means the PULP runs a bit cooler, but the temp guage doesn't read any differently.
Will

I have been getting run-on no matter which fuel I use, for 30 years. The head has been completely rebuilt, polished , matched etc. New camshaft, valves and springs, new pistons, etc and it still runs on. I've played with the timing, replaced the points with Pertronix, changed the cap and wires, and it still runs on, and sometimes, when its very hot - quite seriously - like 2 minutes!! I assume cycling backwards!

I have even checked to see if the float bowls are empty or full after a long run-on, but they're always full. Surley the pump can't still push fuel 2 minutes after the switch has bee turned off?

The only thing not rebuilt in the last 30 years are the carbs. Guess what's next?

Gord Clark
Rockburn, Qué.

Gordon A. Clark

This thread was discussed between 15/01/2006 and 24/01/2006

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