Reply To: compression loss due to hose on gauge

[The red boat]

I just meant that the smaller combustion chambers are more sensitive to the air in the hose as compared to something like a Ford 427. The amount of volume in the hose is miniscule compared to the combustion chamber of a much larger engine but plays a bigger role in a smaller chamber like my outboard.

I understand and agree with the check valve location and its role in the process. I was just wondering if there was a rule-of-thumb factor when using the gauge with a valve near the dial that I could apply to my readings to get a more accurate understanding of my psi.
i.e. – if my gauge with improper check valve is reading 90 psi, can I add 5 or 10 to that to get a reading that more closely resembles a gauge that screws directly into the head (like the $50 mercury one).

thanks for the reply as always!