Does anyone knows how much degrees (BTDC) a 1971 HC 1159cc takes?
I'm confused because the manual says if its a low compression it takes 4.5 deg BTDC or if its High compression its 9 deg BTDC. Anyone knows the difference between them or how to recognise them from standard to Extra Performance?
Thanks.
Ignition timing
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by griffonmark » Sun May 14, 2006 5:52 pm
Hi HC
This brings back memories from when I had a mixture of HB's and HC's in the 70's. There were 3 engines confusingly named low compression, high compression and high performance, and it is easy to confuse them. Really high compression should have been called higher compression, because the high performance engine was the highest compression. From your photos your car is not a high performance model as it has the downdraught carb and not a sidedraught stromberg. The high performance engine and the low compression engine should be at 9deg BTDC, the lefthand of the 2 pointers. You may have the standard (high compression) engine in which case the crank pulley pointer should be aligned between the 2 pointers which is 4.5deg BTDC. Low compression was an option, presumably for when only low octane fuel was available. If yours is a UK vehicle it is probably high compression 4.5deg BTDC. I don't know how to tell the difference, other than the low compression engine had a thicker copper gasket (this may have been replaced) and a compression pressure of 110 lb/sq in, as opposed to 125 lb/sq in. I'd set it at 4.5 deg BTDC. You're a lucky blighter living in Malta, I had my favourite holiday there. Pay my air fares and I'll come out and set it up for you! Regards, Mark
This brings back memories from when I had a mixture of HB's and HC's in the 70's. There were 3 engines confusingly named low compression, high compression and high performance, and it is easy to confuse them. Really high compression should have been called higher compression, because the high performance engine was the highest compression. From your photos your car is not a high performance model as it has the downdraught carb and not a sidedraught stromberg. The high performance engine and the low compression engine should be at 9deg BTDC, the lefthand of the 2 pointers. You may have the standard (high compression) engine in which case the crank pulley pointer should be aligned between the 2 pointers which is 4.5deg BTDC. Low compression was an option, presumably for when only low octane fuel was available. If yours is a UK vehicle it is probably high compression 4.5deg BTDC. I don't know how to tell the difference, other than the low compression engine had a thicker copper gasket (this may have been replaced) and a compression pressure of 110 lb/sq in, as opposed to 125 lb/sq in. I'd set it at 4.5 deg BTDC. You're a lucky blighter living in Malta, I had my favourite holiday there. Pay my air fares and I'll come out and set it up for you! Regards, Mark
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by griffonmark » Sun May 14, 2006 7:57 pm
Hi Chris
I certainly did enjoy my holiday. It was about 3 years ago and I remember going into an old museum with an ancient Austin limousine beautifully preserved. Unfortunately, I couldn't go back the following year and my wife went with my daughter, so she's not keen on going back for a while. I will be back sometime.
In the meantime, have a look at the edge of the head gasket. If its copper coloured or dark bronze coloured, you have LC engine. If it is silvery like normal gaskets then it is probably HC engine. You could always try to time the ignition manually. Start at 4.5 deg BTDC, drive the vehicle up a hill with full throttle and see if it pinks (pre-ignition). If not, advance the timing a bit and repeat the experiment. Keep doing this until the engine pinks. Then back the advance off a touch. If at this setting the engine doesn't pink you have probably got the best setting. Crank and crankcase markers aren't always that accurate, certainly not to 0.5 deg, and an engine runs best with the ignition advance to just below when pinking (pre-ignition) starts.
I certainly did enjoy my holiday. It was about 3 years ago and I remember going into an old museum with an ancient Austin limousine beautifully preserved. Unfortunately, I couldn't go back the following year and my wife went with my daughter, so she's not keen on going back for a while. I will be back sometime.
In the meantime, have a look at the edge of the head gasket. If its copper coloured or dark bronze coloured, you have LC engine. If it is silvery like normal gaskets then it is probably HC engine. You could always try to time the ignition manually. Start at 4.5 deg BTDC, drive the vehicle up a hill with full throttle and see if it pinks (pre-ignition). If not, advance the timing a bit and repeat the experiment. Keep doing this until the engine pinks. Then back the advance off a touch. If at this setting the engine doesn't pink you have probably got the best setting. Crank and crankcase markers aren't always that accurate, certainly not to 0.5 deg, and an engine runs best with the ignition advance to just below when pinking (pre-ignition) starts.
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by griffonmark » Sun May 14, 2006 7:58 pm
Hi Again
I forgot to mention, don't go past 9 deg BTDC! Just in case.
I forgot to mention, don't go past 9 deg BTDC! Just in case.
- griffonmark
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