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Car Forum / MINI / September 2003compression values for an old austin seven
Hi there. I bought an 1961 Austin seven not long ago. It hasn't been started since 1974, so I'm being careful about how I should start it up. I have just done a compression test by placing a little oil through the spark plug holes. Here are the results: cyl 1: 100psi cyl 2: 125psi cyl 3: 100psi cyl 4: 130psi Unfortunately I found no info as to whether these values are ok for me to start the engine. Would anyone know if these measurements are acceptable. kind regards Rob > Hi there. > [quoted text clipped - 15 lines] > > Rob Compression is relative to the compression ratio of the engine and is a sort of standard value. (someone else may have these values) To me this engine will start and you may find that the values may increase with running the engine. Oil gives a false indication of compression - what you have done is seal the rings and taken readings for the valves. ahh ok I see. I placed the oil in there as I was a little concerned that the thin film of oil that usually exist between piston and cylinder would have gone in the 40 years that the engine has not been started. looks like I may have done it the wrong way around. thanks for the advice though ops. another question, I have removed the radiator and hoses. There was no water in the cooling system at all, however in the top radiator hose outlet where the thermostat is I found the whole outlet almost filled up with a strange soft crystal/salt growth. If this growth is present throughout the entire cooling system will it still be ok to run the car? I suspect that most of the crystal growth will dissolve when I fill the system with water and flush it out. Any suggestions/ things to do or not to do?? kind regards, Rob > > Hi there. > > [quoted text clipped - 24 lines] > Oil gives a false indication of compression - what you have done is > seal the rings and taken readings for the valves. Is this for your concourse rebuild or a shed like run around? If it is for concourse you care about this engine so rebuild it. If it is for cheap run-around in a shed - start it, see what happens and if the worst comes to the worst, find a new engine. This age of car wouldn't make a good shed like run-around as things are more expensive to replace. With the pickup (just an example) you can add 1/3 to the price because the panels are apparently gold plated ;) Same for things like Mk 1 floor panels. The Muffin Man > ahh ok I see. I placed the oil in there as I was a little concerned that > the thin film of oil that usually exist between piston and cylinder would [quoted text clipped - 46 lines] > > Oil gives a false indication of compression - what you have done is > > seal the rings and taken readings for the valves. well, I want to keep the car original as I can. I wont be driving it regularly, on one or two times a month to mini club meetings and stuff. However being a student, the extent to which I keep things original is limited to the size of my wallet. I am hoping to run the engine and drive it till it dies, after which I will rebuild it. The car is in perfect original condition except for a missing tail light lens. The panel are totally straight with no rust but the paint work has gone dull and discoloured after being under 30 years of dust. Rob > Is this for your concourse rebuild or a shed like run around? > [quoted text clipped - 61 lines] > > > Oil gives a false indication of compression - what you have done is > > > seal the rings and taken readings for the valves. Start it and see what happens. Try changing everything electrical - plugs leads dizzy cap points condenser etc. Check that the piston in the carb doesn't stick, flush the water and refill, oil down the bores was a good idea - perhaps do that again and then suck it and see ;) If it starts change the oil!! See how far you can drive it :) The Muffin Man > well, I want to keep the car original as I can. I wont be driving it > regularly, on one or two times a month to mini club meetings and stuff. [quoted text clipped - 86 lines] > > > > Oil gives a false indication of compression - what you have done is > > > > seal the rings and taken readings for the valves. > cyl 1: 100psi > cyl 2: 125psi > cyl 3: 100psi > cyl 4: 130psi Gosh those seem low (and certainly not within about 10% of each other). Perhaps if you let the engine wake back up from it's long slumber these values will change. Hate to think what the valves look like (or rings). I have found that every time I go back and redo those measurements. the results are slightly higher. so maybe it will increase once I wake the engine back up. > > cyl 1: 100psi > > cyl 2: 125psi [quoted text clipped - 4 lines] > Perhaps if you let the engine wake back up from it's long slumber these > values will change. Hate to think what the valves look like (or rings). Yeah... as Muffin Man said... I'd fool with it and just see what happens. > I have found that every time I go back and redo those measurements. the > results are slightly higher. so maybe it will increase once I wake the [quoted text clipped - 8 lines] > > Perhaps if you let the engine wake back up from it's long slumber these > > values will change. Hate to think what the valves look like (or rings). First, you should manually turn the engine with the plugs out to make sure it isn't seized. Then leave the plugs out, connect up a battery and spin it over with the starter motor for about 20 seconds. Then let the starter motor cool down and repeat this process until the oil light goes out. Then replace the plugs and try to start the engine. Doing this will ensure you have oil around the engine before you start it, reducing wear when it does start.  SignatureRgds Steve steve@dsnclassics.co.uk www.dsnclassics.co.uk |
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