rattle/grind, lower rear of motor

[fireguy12117]

i got my new heads on this weekend, buttoned up the motor today, took it for a test drive and everything seemed fine until i pulled back into the driveway. when i parked it i noticed a grinding rattling noise. I've had some issues with the AC compressor, but wasn't it- however i did notice some odd correlations:

the noise seems to be coming from the bell housing of all places and more or less disappeared when i turned the AC off, reappeared with the AC on, and its repeatable that way. with my foot on the brake and shifting between park, reverse or neutral to drive i think i hear it for a second as the RPM's rise and drop between gears.

so, best i can tell is i never heard this since putting a new rebuild in because that rebuild always idled pretty high. now the engine idles around 700 and it seems like its a low idle speed, extra engine load that causes a noise at the rear lower end of the motor...WTF is this...

I'm going to drive this a few days, see if it gets worse or goes away. right now all i can think is perhaps a loose flywheel that when it gets slowed just enough that cintrifigual forse loosens up and it starts to rattle. Eons ago i remember being in a work van with a cracked/busted center of a fly wheel. it would start the van, but rattle like all get out until the van was moving.

 

[Big Jim M]

I'm assuming

you took the compressor off to install the heads.. Have you retorqued the compressor since the noise started? I think I'd be looking at the compressor as the noise maker and not the other end of the engine..
Big JIm

 

[Dusty_Ranger]

check your starter bolts thats what mine was

 

[fireguy12117]

its distinctly at the bottom rear of the motor. i originally thought of the AC as the last time it was on the road there seemed to be a bearing noise but when i was poking around i wound up on a creeper under the truck.

i will be double checking tightness on everything regardless. i know how sound can travel on a car...