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MG MGB Technical - Lead free head

Is there any way of telling if a head is lead free apart from valve recession. I rebuilt my engine in 89 and didn't give it a thought at the time. the engineering was done at Nick Stagg of Yate near Bristol, he was quite well known for Mini and Escort performance engines and he supplied me with a "GSC" stage 2 head.
At that time the switch over was just starting with many major manufacturers fitting lead free heads ( though not Leyland ) But not many filling stations stocked lead free petrol.
I always used either leaded or LRP which was available locally up to about a year ago. But now I wonder if it was supplied as a lead free head, I'm sure heads that were supplied for fords at that time would have been leadfree.
c cummins

The "lead free" conversion generally consists of inserting hardened valve seats for the exhaust valves and upgrading the quality of the exhaust valves. Intake valves do not run as hot at the exhaust valves and do not require hardened seats although some prefer to have them installed at the time the conversion is accomplished. I do not have then installed on my cylinder heads unless needed to bring the seats back to the proper size to work with the intake valves. (As valve jobs are done over the years, the seats are cut away and the valves cut to clean them up and match them to the seats. Over a period of time, this can result in an enlarged seat area which, unless valve seat inserts are fitted, would have the valves sitting too deep in the cylinder head.)

So, you can see from this description that there are two ways to check for an unleaded conversion. First is to have a receipt from a reliable rebuilder showing that the conversion has been performed. Second is to remove the head, clean the combustion chambers, and do what is necessary to see if inserts have been installed for the exhaust valves.

Cylinder heads which have been operated with leaded petrol for several years are believed to be be capable of operating with unleaded fuel for a number of years without trouble. Hard to say, as a hobbyist, whether this is true or not. But, my experience with several vehicles designed to run on leaded fuel and run on such fuel for many years was that the advise is true. They ran for many tens of thousands of miles, on unleaded fuel, without damage to the cylinder heads.

You will have to decide what is best for you.

Les
Les Bengtson

Les pretty much filled you in with the details. The only thing I would add is to keep up with valve adjustments, and note if the lash gets too much smaller in too few miles. If it keeps getting smaller too quickly, the valves are receding. If not, you are okay.

Anyway, I would not bother to do anything about it unless it presents a problem. The only exception to that might be if you are planning a big long cross-country trip of ten thousand miles or so. In that case, I might pull the head to check it preventively.

Charley
C R Huff

Sorry, but non hardened inserts could have been fitted too - the only way to tell if an insert suitable for unleaded fuel is fitted is for it to be recut by an engineer used to dealing with hardened inserts - they will be able to tell whether they are hardened or not by the way they cut.
Chris at Octarine Services

Chris, is it always the case that if bigger valves are fitted as in this case for a stage 2 head, that inserts would be used?
c cummins

No - there is generally no need to fit inserts on the inlets unless seat erosion has taken place.

Exhausts are always 1.34" dia unless it is a supercharger head.
Chris at Octarine Services

This thread was discussed between 01/09/2009 and 03/09/2009

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