jayzx10r Posted March 17, 2013 Report Share Posted March 17, 2013 Before I get a bunch of crap for having old tools, my dad gave me this gauge when I was a kid and it would feel wierd to toss it away. Last time I tested it against a Snap-On screw in style, it showed the same PSI on a 454 cylinder. That being said..... I have an old school compression tester, the type with the rubber sleeve that you push against the top of the spark plug hole. The newer style (post 1995 lol) screw into the plug hole and displace some of the vollume, probably giving a more accurate reading for small displacement motors, like the 175cc Banshee, If I show 150PSI based on measuring cylinder head volume from the outside edge of the spark plug hole, what would you estimate my true compression to be? I'm running a 50/50 mix of 100LL and pump premium and still getting detonation/pre ignition. Thanks, Jay. Quote Link to comment Share on other sites More sharing options...
Finch Posted March 17, 2013 Report Share Posted March 17, 2013 160 Quote Link to comment Share on other sites More sharing options...
Finch Posted March 17, 2013 Report Share Posted March 17, 2013 and whats the winner get? Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted March 17, 2013 Report Share Posted March 17, 2013 Deto at 50/50? I'll go with 174 Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted March 17, 2013 Report Share Posted March 17, 2013 in my opinion mixing 100LL and 93 octane is an absolute WASTE......if your running that mix and still getting deto then just run straight 100. Doing a mix of 50/50 will only give you a rough octane number of 96.5 its not worth mixing. now mixing 110 and 93 would give you a rough octane of 101........which would be better than what your doing. Quote Link to comment Share on other sites More sharing options...
ATVridinMaNiAc Posted March 17, 2013 Report Share Posted March 17, 2013 I use the same type of compression tester its an old Hastings one in a yellow case has different pieces to it but it has that rubber piece you just push up against the plug hole. i cant imagine it being off my much...it read 115 and 120 on my banshee right before i tore it down and on my dads it read like 135 after we rebuilt it and thats on a banshee with a stock head and .020 overbore. Quote Link to comment Share on other sites More sharing options...
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