maskmanLS6 Posted May 3, 2012 Report Share Posted May 3, 2012 Ive gotten different readings from different gauges on the same engine within two hours of run time. Each gauge reads the same as it did before so my compression is the same but why do the gauges read so different from each other? Does the length of the insert need to be the same as the spark plug shank? The gauges ive tried have had different lengths and im thinkin that could be the reason for the difference in readings. The one thats the same length as the spark plug gave me a 140psi reading and thats the one im going with. The other gauge had a shorter insert and gave me a 125psi reading. Any input on this would be helpful. Thanks Quote Link to comment Share on other sites More sharing options...
SAVAGE420 Posted May 3, 2012 Report Share Posted May 3, 2012 Yes It has to be the exact same length or you won't get an accurate reading on the gauge. So the 140 would be your accuracy reading. Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted May 3, 2012 Report Share Posted May 3, 2012 Ive gotten different readings from different gauges on the same engine within two hours of run time. Each gauge reads the same as it did before so my compression is the same but why do the gauges read so different from each other? Does the length of the insert need to be the same as the spark plug shank? The gauges ive tried have had different lengths and im thinkin that could be the reason for the difference in readings. The one thats the same length as the spark plug gave me a 140psi reading and thats the one im going with. The other gauge had a shorter insert and gave me a 125psi reading. Any input on this would be helpful. Thanks You've allready answered your own question. A good guage will have a thread the same length as the plug and will have the schrader valve in the very end. This will duplicate actual (as running) chamber volume the best and give you the most accurate readings. Other factors are the guage itself may be of a better or lesser quality and therefore read differently. But, the compression test is only to determine/monitor the engines internal condition and should be used only for that purpose. Record your results and always use the same guage to do future compression tests. -Brandon Quote Link to comment Share on other sites More sharing options...
maskmanLS6 Posted May 3, 2012 Author Report Share Posted May 3, 2012 Yes It has to be the exact same length or you won't get an accurate reading on the gauge. So the 140 would be your accuracy reading. Thats what i was thinkin too. Thanks for the input to help me confirm, Its always good to have a second word of wisdom. Quote Link to comment Share on other sites More sharing options...
maskmanLS6 Posted May 3, 2012 Author Report Share Posted May 3, 2012 You've allready answered your own question. A good guage will have a thread the same length as the plug and will have the schrader valve in the very end. This will duplicate actual (as running) chamber volume the best and give you the most accurate readings. Other factors are the guage itself may be of a better or lesser quality and therefore read differently. But, the compression test is only to determine/monitor the engines internal condition and should be used only for that purpose. Record your results and always use the same guage to do future compression tests. -Brandon Makes since to use the same one because whether its right or not your base number is what counts and any less on the next test will indicate wear. Yea its making more since to me now, Thanks for the advice and wisdom. Quote Link to comment Share on other sites More sharing options...
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