I have heard that some people have hard valve seats fitted to their A7. I have been driving mine for about a year.Is this necessary? I thought that we had no tangible problems with valve seat damage due to the use of unleaded fuel. Stan.

Hi, ive been running my box for 15+ years on unleaded and had no problems.I used to check the valves for diminishing clearance but got bored when I found no change year after year. I dont think the valves have sufficient velocity to damage themselves. Anyway historically weren't austins designed to run on unleaded which was only introduced around ww2 for aircraft engines?
Andy

Correct about originally A7's ran on unleaded fuel, however - and it has been discussed elswhere many times - the burn cycle and temperature of modern petrol is different to that in the 30's, plus UK fuel is 95 Octane, whereas prewar fuels were probably in upper 80's. Modern valve timings also allow for the unleaded burn cycle. Use an additive and don't thrash the engine and you should be OK.

My modern Volvo 740GLE (alright, 1989) is pre unleaded, but the supplier told me that as long as I don't thrash the engine (80mph in overdrive eqautes to about 2,900 rpm) keeping below 3,000 revs there should be no problem, 120,000 miles later (190,000 total) I still have no problems.

Phil

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Phil,

You are advising the use of an 'additive'. I wonder which one it is that you use. I used a major oil company version for about twelve months and it only caused me to stop every sixty/seventy miles to clean the jets.

As an experiment I stopped using it and I have not experienced the problem in the last two thousand plus. All other relevant things being unchanged.

Perhaps there is something that I am missing - brain apart that is.

Mike

Mike, In the A7, I'm using Castrol additive without any problems in the jets.

Phil.

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Phil,

Thanks for that.

I shall have to give it another try, if only out of curiosity. It is strange. Perhaps it is peculiar to Hampshire petrolium spirit.

Mike

Hi All,

The problem with valve seats burning away happens quicker at high revs than at low revs and if you plot a graph it has an accelerating curve from about 3000 rpm. At 4000 rpm it is beginning to be a problem , at 4500 rpm it is a major problem and at 5000 rpm plus you are doing damage to the valve seats at a very quick rate. As normal road Austin Sevens usually only reach 3000- 3500 rpm then there really is no problem. Many of the Austin Seven long distance drivers in Cornwall put no additives in their petrol and after 3000- 4000 (or more ) miles a year we have not found any problems.

A little dash of Redex might help but a rarely use that so let's all stop worrying and get on enjoying the open road in front of us!!!