Bypass valve noise (Page 1/1) jmac87tt SEP 16, 03:58 PM Just started up a l67 rebuild. Heard what sounds like a high pitch scream with any kind of throttle. Not like a good blowing whine more of a motor starting with a belt that needs service. I've narrowed it down to the bypass actuator being activated anytime it's heard. Any ideas what this could be ? Car does have a 2.5" short stack intercooler on it jelly2m8 SEP 17, 05:34 AM I think a good quality video of what you are hearing is needed. before anyone needs an intercooler or small or blower pully is an actual dyno run showing Spark knock. Never ever Mod a 3800 before you have a valid dyno pull with out Data first. jmac87tt SEP 17, 10:51 AM It's an initial start up and with no drive time I'm not worried about the tune being any kind of issue with this problem, a base map has been formulated/written with the mods in mind with the intention dyno tuning after initial start up. We been doing that since the 80s never started a single one on the dyno.