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Feb 21, 2017 10:40 am
Feb 21, 2017 10:40 am
Subject: Re: Meadows Engine Help
Hi all,
Some interesting comments here. May I add my peneth worth.
The lower the compression the slower the burn and generally a worse burn but not always if setup really well and a very well designed engine, there are reasons for running low compression even now but would go out of the realms of this thread.
The low compression and slow burn does as is already mentioned, give more time to heat pistons, bores and combustion chambers etc and can cause a hot engine.
Too high a compression ratio can do the same for different reasons, Detonation for example, this is when the fuel near the spark plug ignites, as the flame is progressing across the combustion chamber, the yet to be ignited gasses are getting very very hot, if they get too hot before the flame progresses correctly then they explode causing detonation and a severe load on pistons and bearings etc.
We have to remember that the combustion process is a carefully timed "burn" not an "explosion"
Now on to Volvo pistons,
These are ok pistons to use and do work, BUT you need to do three things to make them work ok.
1. Volvo pistons are made for floating piston pins, the Lagonda has a pinch bolt. So in order to let the pin work correctly you will need to loosen the clearance in the piston slightly, this should be set so that the pin does not go tight at any time, even with a cold piston. Otherwise bore/piston damage will occur very quickly.
2. Run a piston to bore clearance of 0.004" minimum, Lagonda engines do not cool evenly on all bores and in order to keep things from seizing this is a strong recommendation.
3. The run in period and process. Piston speed is not an issue on this engine if running at sensible speeds, it's well inside std levels.
However the load of a heavy car running low RPM and relatively low compression ratios (even 8:1 is considered low) the probability for problems due to heat buildup is at its greatest. Maximum danger point is low rpm coupled with heavy load. So at 1500 rpm for instance and max throttle you will kill your new engine dead! Light load and more rpm are much better for running in.
I always always always run the following procedure.
A: With ignition off, turn engine to get oil pressure.
B: Run engine in car for 5 minutes at 2000 rpm with no load.
C: Turn off and check
D: Drive car at no more load than if you were driving on a flat road with the smallest throttle opening possible. RPM up to 2500 and no lower than 1800 is fine. 5hours engine running
E: Drive at similar conditions but using only slightly more throttle, really very little but again RPM is fine up to 2800 but no lower than 1500. 5 Hours
F: Drive as if on a very gentle drive with an egg under your foot. same rpm as E but no more than 1/3 throttle. 1 Day of good driving
G: Drive again in the 1500 to 2800 rpm range for another day of real driving using no more than 1/2 throttle, (my advice is to set max throttle to half position to make things easy) Again though imagine that egg under your foot.
H: Setup day, drive and use the car as if driving on a long trip in the gentle hills of the Berkshire downs (feeling home sick now) with the odd full power run on a flat road, rpm up to 3300, (tip here, if the engine goes well up to 3k but loses some power thereafter, richen it up, I find this a lot but nowadays do all these tests with a Lambda fitted and usually on a rolling road but not always)
I: Enjoy your car with very little to worry about.
Don't let your engine get above 90 degrees at any time during the running in period. Avoid like the plague! Some places will be over 100 when your gauge is reading 90. The gauge is an average meter remember and don't use a thermostat in a Meadows 6. You have been warned and would be amazed how poor the circulation is. Although if all is up to scratch, they generally don't overheat.
Hope this helps.
Julian
Hi all,
Some interesting comments here. May I add my peneth worth.
The lower the compression the slower the burn and generally a worse burn but not always if setup really well and a very well designed engine, there are reasons for running low compression even now but would go out of the realms of this thread.
The low compression and slow burn does as is already mentioned, give more time to heat pistons, bores and combustion chambers etc and can cause a hot engine.
Too high a compression ratio can do the same for different reasons, Detonation for example, this is when the fuel near the spark plug ignites, as the flame is progressing across the combustion chamber, the yet to be ignited gasses are getting very very hot, if they get too hot before the flame progresses correctly then they explode causing detonation and a severe load on pistons and bearings etc.
We have to remember that the combustion process is a carefully timed "burn" not an "explosion"
Now on to Volvo pistons,
These are ok pistons to use and do work, BUT you need to do three things to make them work ok.
1. Volvo pistons are made for floating piston pins, the Lagonda has a pinch bolt. So in order to let the pin work correctly you will need to loosen the clearance in the piston slightly, this should be set so that the pin does not go tight at any time, even with a cold piston. Otherwise bore/piston damage will occur very quickly.
2. Run a piston to bore clearance of 0.004" minimum, Lagonda engines do not cool evenly on all bores and in order to keep things from seizing this is a strong recommendation.
3. The run in period and process. Piston speed is not an issue on this engine if running at sensible speeds, it's well inside std levels.
However the load of a heavy car running low RPM and relatively low compression ratios (even 8:1 is considered low) the probability for problems due to heat buildup is at its greatest. Maximum danger point is low rpm coupled with heavy load. So at 1500 rpm for instance and max throttle you will kill your new engine dead! Light load and more rpm are much better for running in.
I always always always run the following procedure.
A: With ignition off, turn engine to get oil pressure.
B: Run engine in car for 5 minutes at 2000 rpm with no load.
C: Turn off and check
D: Drive car at no more load than if you were driving on a flat road with the smallest throttle opening possible. RPM up to 2500 and no lower than 1800 is fine. 5hours engine running
E: Drive at similar conditions but using only slightly more throttle, really very little but again RPM is fine up to 2800 but no lower than 1500. 5 Hours
F: Drive as if on a very gentle drive with an egg under your foot. same rpm as E but no more than 1/3 throttle. 1 Day of good driving
G: Drive again in the 1500 to 2800 rpm range for another day of real driving using no more than 1/2 throttle, (my advice is to set max throttle to half position to make things easy) Again though imagine that egg under your foot.
H: Setup day, drive and use the car as if driving on a long trip in the gentle hills of the Berkshire downs (feeling home sick now) with the odd full power run on a flat road, rpm up to 3300, (tip here, if the engine goes well up to 3k but loses some power thereafter, richen it up, I find this a lot but nowadays do all these tests with a Lambda fitted and usually on a rolling road but not always)
I: Enjoy your car with very little to worry about.
Don't let your engine get above 90 degrees at any time during the running in period. Avoid like the plague! Some places will be over 100 when your gauge is reading 90. The gauge is an average meter remember and don't use a thermostat in a Meadows 6. You have been warned and would be amazed how poor the circulation is. Although if all is up to scratch, they generally don't overheat.
Hope this helps.
Julian