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MG MGA - Using Lead-Additives

Quick question.
Now that I am driving my car quite regularly, I was wondering if I would need to add lead-substitutes.
I bought one of these products when I first got the car, but I have not used it yet.

Assuming that I have no idea about the valve seats, or the condition of the cylinder head/valves, would you recommend I use it as a precaution until I know what the condition of the head?
Would it be beneficial or detrimental.

I have been using premium fuel. i.e 97 I think.

Just want to make sure I am not damaging the engine by running it with unleaded...

I read some of Barney's pages, but they assume that you know what valve seats are in your cylinder head.

Comments appreciated.
Gonzalo Ramos

I couldn't say if any of those additives are actually detrimental. Some of them might actually do a little good, while others are almost certainly worthless. My personal view is that the additives are expensive enough that they are not cost justified, even if they might actually do a little good. Best advice is to drive it without fuel additives as long as it runs well. When it finally needs some cylinder head work (which will be soon enough regardless), then install hardened steel valve seats and maybe bronze valve guides. If you plan to drive it a lot, or drive it hard for competition or trailer towing, then also include Stellite exhaust valves.
Barney Gaylord

I ran my un-modified ZA Magnette for years on unleaded fuel without any noticeable problems until I eventually did a complete engine overhaul. The valves and seats didn't look any different to what I would have expected on a high-mileage engine that had been running on leaded fuel. When the UK first went to unleaded fuel, there was a period when both unleaded and 4 star leaded fuels were available. During this period, I used to alternate between the two fuels, and to my surprise, found that the ZA ran better on the unleaded fuel! My 1975 Series 3 Land Rover, again un-modified with regard to valves and seats, has been running on unleaded fuel without any extra additives since 1992 and still runs beautifully, for a Land Rover anyway!
Lindsay Sampford

Ok, well thats good news. The car runs fine so far and has good power. I can take it up to 7000rpm on big accelerations without issues!

As a last note, do you also recommend I continue using premium fuel or should I try the cheap stuff (85 I think) to see if I see a noticeable difference?
My understanding is that this could cause pinking/knocking but I am not sure if I would be able to detect it myself, given my limited experience.
Gonzalo Ramos

I always run my MGA on the cheapest grade of pump fuel available (usually 87 octane with 10% alcohol these days). But I should qualify that with saying I built it to run that way. It has a fast street cam but no increase in compression ratio, and it will not ping under any circumstances. Maybe I could have a little more power with higher CR, but for all the driving I do there is an economic advantage to using cheap fuel.
Barney Gaylord

Gonzalo
You would definitely notice if your engine was pinging a lot ( we call it "pinking" in the UK )
It is a high frequency rapid metallic tapping noise from the engine when you accellerate. It is usually worse if you try to accellerate in too high a gear when you should really have changed down a gear and it it tends to stop when you back off the throttle a bit.
Many MGAs ping a little bit without causing any problem but an excess level of pinging can damage the valve seats and erode the combustion chambers.

On an standard MGA engine it usually can be stopped or reduced by retarding the ignition a little.

Also, I wouldnt rev your car to 7000rpm Gonzalo, most MGA owners that I know never rev beyond 6000rpm. There is plenty of power available up to there and you are risking either lots of engine wear or something major breaking in your engine.

Does anyone else out there rev to 7000rpm with a standard engine? or am I just being over cautious!

Colyn
Colyn Firth

I am was somewhat surprised at Gonzalo's comment re 7000rpm..I personally never take my mga above about 5000rpm and would suggest that 7000rpm is more than a little excessive. I would be waiting for a metal clatter if I drove much time at above 5500.
I was interested in Barney's and Lindsay's comments re lead and fuel. I use a lead replacement fluid called Flashlube at 1cc per litre and don't notice the cost ( buy in bulk) and have done so for about 5 years..since leaded fuel became near impossible to obtain here in Oz. I run on lowest grade fuel ( but no courage for alcohol...not in the tank anyway!). I have not had the head off for about 15 years ...
On the basis of ignorance and it is doing no harm I will stay with the additive ..if I have to work the head then time for new hard seats etc..
Neil Ferguson

Yes 7,000rpm on a standard engine with unknown history is asking for trouble. High rpm is one of the best routes to use for accelerated engine wear, and possibly worse!

For myself, normal driving, or at least around built up areas I probably stay between 1,500 and 4,000. Moving up to 2,500 to 5,000 for more spirited "open road" driving. I maybe touch just over 5,500 if I am really trying to keep speed when changing up to third, but not often.

If your engine has been rebuilt specifically to be driven at high revs, (presumably with a track in mind) then of course that's different.
Neil McGurk

Neil in Oz,

In the interests of caution I would carry on using the "Flashlube" as before and then urgently check the valve seats and combustion chambers for damage in about another 15 years or so!

Like you I would leave it be, Im sure you would have noticed before now any excess pinking that could cause some damage.

Colyn
Colyn Firth

Ok, just to clarify. I don't run it to 7000rpm regularly. It might hit that just for 1/2 a second when accelerating fast into 3rd or 4th gear. I am aware I should not be doing that too much.
I will try to use regular fuel next time see what the difference is.
Since i've had the car I have not touched the timing at all...may be a good opportunity to check it if it 'pinks'.

Thanks for the help guys!
Gonzalo Ramos

Don't know about the rest of you, but my tach shows the redline at 6000 rpm. I don't race my car and even with 'really spirited' driving, I don't think I've ever pushed it beyond 5500.
Andy Bounsall

Regarding unleaded fuel in cars without hardened valve seats, I once read that cars that had been using leaded gas for many years, have lead "embedded" in the valve seats, and so the use of unleaded gas is not too hard on the seats until after many miles. Not sure what "many miles" meant....
G Goeppner

Gonzalo -- must say I agree with Neil McGurk on this unless you have a special cam shaft and balanced engine.
The power peaks at around 5600 rpm on the standard 1600 and 1622 engines and above that you are over the top of the curve and all you are doing is stressing the engine.
There is also bags of torque for pulling at those revs
so ..... Have fun but ...
David
D C GRAHAME

This thread was discussed between 06/05/2010 and 07/05/2010

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