(SBF 302) very BAD vibe around 3500RPM's..

**Jacob** · 09-08-2014, 07:04 PM

Also,
One thing im worried about is the main cap..I have no ideal how long the guy I bought it from drove it so will the main cap the bearing spun in be OK ??
Also,
Lets say I took the one cap off and took the bearing out..If the crank is smooth,could I just put a new bearing in and torque it down to spec and call it a day??

**fastredgmc** · 09-08-2014, 07:21 PM

if the main was spun it would have low oil pressure also would cut the oil off to the rods and the rods would be knocking. Would be alot lot louder then a tick when you take off and would make a noise all the time. Not doubting the mains could be worn out from driving with a vibration though.

could possibly be a bad thrust bearing in the engine to . You could check that quick by pulling off the belt and grabbing the balancer and pushing in and pulling out or have somebody push the clutch in and watch the ballancer move.
If you have a dail indicator you can measure easy shouldnt be a whole lot more the .010". crank will walk back and forth and destroy the seal quick could possibly have a vibration

**Jacob** · 09-08-2014, 07:47 PM

Now that you said that,it reminded me of this..Right around the time the rear seal let go my oil pressure gauge was acting funny..At idle,the gauge would bounce from having oil pressure to non..Its a HV pump so I thought it was the gauge and planned to buy a Autometer so yes,my oil pressure was acting goofy..Maybe im not explaining it right but the tick isn't like a lifter tick..I'll be more than happy to bring it by some time this week if you could check it out real quick??

**fastredgmc** · 09-08-2014, 08:14 PM

Well if you have no oil pressure thats a big thing. No sense to beat a dead horse more. ID confirm that and if no oil pressure tear it down and see whats going on

**Jacob** · 09-08-2014, 08:58 PM

I'll find someone to look at it before i do anything...Thanks everyone

..

**Jacob** · 09-09-2014, 01:42 PM

Checked the crank and can't move it at all..Going to put the car on stands,unbolt the oil pan and motor mounts..Then lift it with the picker,slide the pan out and start replacing main bearing because im sure now that the back one spun in the cap..Just gotta wait until I have the time and hoping my mom lets me use the garage for a day or so...

**OldbutNew** · 09-09-2014, 04:22 PM

Dude, If the #5 main bearing is spun in the cap, the engine has to come out. Putting a new bearing in there is putting a band-aid on sliced artery.

The block and cap will now be out-of-round and most likely oversized, not to mention the crank journal being jacked. The typical repair process for a spun main involves cutting the main caps by somewhere between .020" and .040", then line-boring the block back to round, straight, and the correct size. Same issues with the crank journal. On top of that, the metal debris from the steel-backed bearing spinning at a couple thousand RPM inside a cast-iron block and cap is like a lathe. ALL those chips are going somewhere. A lot of them went onto the piston skirts on #4 and #8. A lot more probably went into the #8 rod bearing until the main stopped feeding oil to it. The it turned into a lathe too.

I hope you find out that it's something else.