8 hours ago
Hi
The overbore will have increased the CR by maybe 5%, i.e. not much.
Compression gauges are probably only accurate to +/- 5% so might be slighly over reading.
The head may have been skimmed, which will also up the CR. You could measure this externally.
In the old days a severe build up of carbon would have been a reason, but with modern fuel and oil it's less likely
I am not aware of any thicker head gasket options. In desperation you could try using two standard HC gaskets but it will reduce heat flow from the head.
However, I wouldn't immediately think that a raised CR would lead to a serious drop in performance. Is the exhaust free flowing, i.e. not choked up ?
The overbore will have increased the CR by maybe 5%, i.e. not much.
Compression gauges are probably only accurate to +/- 5% so might be slighly over reading.
The head may have been skimmed, which will also up the CR. You could measure this externally.
In the old days a severe build up of carbon would have been a reason, but with modern fuel and oil it's less likely
I am not aware of any thicker head gasket options. In desperation you could try using two standard HC gaskets but it will reduce heat flow from the head.
However, I wouldn't immediately think that a raised CR would lead to a serious drop in performance. Is the exhaust free flowing, i.e. not choked up ?