28-12-2020, 06:06 PM
When I originally bought my RN I checked the cylinder pressures and they all came out 45/50 psi. The car ran pretty well and achieved the performance a standard car of this type expects.
I decided to do a thorough refresh this winter primarily with the top end.
Having done a thorough job including replacing all the valves with new, cutting the seats etc. I now have a compression pressure of 51/52psi across all four pots.
I'd Expected it to be in the 80/90 psi range. the engine runs like a little sewing machine and pulls as well as I would expect but I can't explain the pressures.
I'm a retired mechanic and experienced engine builder and have built loads over the years, particularly race engines, but new to the quirks of the Austin 7.
I've even checked the gauge against my compressor and they agree exactly.
The bores are perfect with +40 pistons that look like new and come level with the block face at TDC
What's throwing me is that all four pressures are almost exactly identical which is making me wonder if I have some mismatched parts from a previous owners build, i.e. wrong head or whatever.
As I said the engine starts instantly and runs sweetly and seems to have the requisite power but it's stumping me, any suggestions would be most welcome
Buy an Austin 7 they said, It's easy to work on they said !
I decided to do a thorough refresh this winter primarily with the top end.
Having done a thorough job including replacing all the valves with new, cutting the seats etc. I now have a compression pressure of 51/52psi across all four pots.
I'd Expected it to be in the 80/90 psi range. the engine runs like a little sewing machine and pulls as well as I would expect but I can't explain the pressures.
I'm a retired mechanic and experienced engine builder and have built loads over the years, particularly race engines, but new to the quirks of the Austin 7.
I've even checked the gauge against my compressor and they agree exactly.
The bores are perfect with +40 pistons that look like new and come level with the block face at TDC
What's throwing me is that all four pressures are almost exactly identical which is making me wonder if I have some mismatched parts from a previous owners build, i.e. wrong head or whatever.
As I said the engine starts instantly and runs sweetly and seems to have the requisite power but it's stumping me, any suggestions would be most welcome
Buy an Austin 7 they said, It's easy to work on they said !
Buy an Austin 7 they said, It's easy to work on they said !