1974 silver starflite 135 compression

[nagasama]

ok, i had a post earlier with some compression numbers that i thought were accurate.<br />i was using a rubber tipped gauge, did not have the plugs out, and only bumped the starter until i got a reading.<br />they were in the 112-118 range. pretty good.<br />i got a new screw in type gauge.<br />i took the plugs out.<br />i turned the engine over for five seconds.<br />readings are:<br />cyls 1, 2 &4: 155...exactly, all three<br />cyl 3: 160<br />three questions:<br />am i performing the test correctly?<br />and (if so)<br />are these readings not friggin EXcellenT for this thirty year-old beast? <br />is there such a thing as too much compression?

 

[javsam]

Re: 1974 silver starflite 135 compression

the way I do it is, warm up engine to operating temp. then take out all spark plugs. then set throttle to wide open.then crank engine 5 compression strokes.the battery should be fully charged before you do this test and I like to use the screw in compression testers made by sun.<br />Test results should be readings within 25 percent of each other.<br />javsam

 

[JB]

Re: 1974 silver starflite 135 compression

The important thing is that you do each cylinder exactly the same as the others.<br /><br />You have demonstrated how much psi readings can be changed by changes in guage and technique. That is why it is rare to find psi criteria in Service Manuals.<br /><br />I don't think I would like readings that varied by 25%. I prefer to set the bar at 10-15%.

 

[RobsTV]

Re: 1974 silver starflite 135 compression

Actually, those appear fairly normal numbers for that motor if in good shape. Do a search of 135HP, and I don't think you will find any at less than 135-140 PSI. Any other motor and they would be excellent. Almost the same numbers here with '75 135HP (142-152PSI). All other threads state same results from other 135HP V4 owners as well. Great motors that even after 30 years still going strong.