Strange LOUD vibration from engine 3250-3750
 

Hey guys, was hoping I could get some extra folks in on this to help me think up what this could be. Sound is best heard between 1:30 to 1:45 in and appears to come from the top/back of the engine but it's pretty cramped in there. Just started happening recently. Boost, vacuum, idle, revving outside this range is unaffected, though sometimes the vibration follows the engine RPM above 3750 but it gets substantially quieter as the RPMs climb until it is inaudible. My buddy says it could be lifter noise due to the gap opening up, but that would be through the whole range no? I doubt I spit a SUB shim because I know what that sounds like.:bang:



I'll be jacking the car up later to drain the oil and then pulling the oil filter to cut it up but any suggestions before I get to that is appreciated.

That sounds a lot like lifter tick to me. Is the oil pressure normal? When was the last oil change? Is it a recent problem?

Fairly recent yeah, actually around the time I switched to e85. Going to switch back to 91 when I run it low.

I had another person suggest it could be a rod bearing, but it does sound like it's coming off the top of the engine. I'll be finishing fixing my DD tonight and I'll pull the valve cover off when I pull the car in tonight. Maybe I just have a need to shim my valves or something.

Rod bearing wouldn't be over only a certain rev range it would be constant no matter the revs. My guess is the valves need to be adjusted there is a lot of what seems to be valve train noise in that video. It it isn't an obvious problem blackstone labs do oil tests on motors and can tell you if there is bearing material in the oil you can not see. That saved me one of my Subaru motors. Hope you figure the problem out. Curious to see what it is.

Check the cam pulley bolts.

Worth checking: I left a cam cap loose awhile back and it made a similar racket. Ive also had my fm coil bracket break a mounting tab and rattle like that against the valve cover..

It sounds like you have a lot of lifter noise all the time, and something loose and rattling at the RPM range you mention.