Knocking sound coming from supercharger

mcate

Registered User
At least, it SOUNDS like it's coming from the blower. Just got the car running today with the newly rebuilt & maganported blower. I checked the fluid, & there's fluid in it. I don't think it's the belt tensioners, because they all have really low mileage on them. It's definitely not the alternator. I took the belt off the blower & rotated it back & forth, & I hear that same sound. Any ideas that WON'T confirm my worst suspicions?
 
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Sometimes when they have been ported extensively, they make a knocking noise at idle. Does it go away when you increase the rpms?
 
my 94/95 style blower was ported about 3/8" all through it and it makes the same sound....i was told it was because it has new rotors and a solid coupler....
 
supercatxr7 said:
Sometimes when they have been ported extensively, they make a knocking noise at idle. Does it go away when you increase the rpms?

To be honest, I haven't checked. I've been leery of increasing RPM's until I hear more from people on here. I'll check it out this evening after work.
 
ported blowers like the mp and my D shaped make a noise . its caused by the rotors being unloaded and then loading.

by opening the port up we unload the rotors sooner than a stock setup.
and the rotors clank. its in the gears up front.

soon as there is boost it dies down. yeah mine sounds like the blower on mad max when it kicks in like marbles in a blender. but the added boost and flow make up for it.

my stock blower on my engine with ported heads and exh manifolds only made 10 lbs down from 13 it did with stock heads.

after porting blower it makes 13 lbs with stock pully .
and ported heads.

so its worth the noise
 
The solid coupler transfers more noise than the spring type coupler. If you have bad snout bearings or rotor pack bearings it will transmit that noise into the case.
 
I drove it around today. A friend of mine out here has a magnaported blower on his car, & it makes a noise similar to mine. His is more of a chatter, however, & mine is more of a clacking or tapping sound. I definitely don’t notice it as the engine revs. It does it a lot worse when the engine is idling in gear than in neutral. I’m going to take it to a dyno shop tomorrow to let the guys there look at it, but I’m pretty certain there’s something wrong.
 
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The sound you are hearing is most likely to the reasons above, ecspecially if it goes away when the car is in neutral. I have had to blowers that were extensively ported that did the same thing.
 
supercatxr7 said:
The sound you are hearing is most likely to the reasons above, ecspecially if it goes away when the car is in neutral. I have had to blowers that were extensively ported that did the same thing.

I wouldn't say it goes away in neutral, it's just less noticable. And I don't hear it at all when the engine is revving. But it's VERY noticable when driving through a parking lot.
 
Well, I pretty much confirmed today what's wrong. I went over to a buddy's & rotated the shaft back & forth on his extra blower, & there's no play. Mine on the other hand has a good quarter of an inch of play. Probably a bad coupler. At any rate, it gets shipped back to Magnum Powers tomorrow.
 
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