After rebuild had bad vibration. First thought was maybe I switched a few pistons while rebuilding. Don't know what that would do. Going to switch harmonic balancer and see if that makes a difference.
Hi,
Was this a stock rebuild, OE parts, stock reciprocating assembly, or used with aftermarket internals? Piston reliefs?
What year is the Motor? The 3.8’s were externally balanced until late 00’, then went internal balance in late 00’ to 04’.
We did have a 99’ that took us by surprise as it was IB, and was never rebuilt previously.
Is this a 5 Spd? Some Mfg’s actually sell neutral balance & external balance Flywheels, Flexplates and Dampers as they used the same part #, you need to pull the offset weights yourself if running IB.
Other possibility is a belt driven accessory, yank the SERP & see if it clears up, and others I’ve had Clutch assemblies that actually threw new motors off for a few days, as I recall, sent a general shop laborer to the customers home to pull the Clutch & Flywheel and the ring gear was actually welded on crooked.
Some Aluminum Flywheels w/steel inserts made for IB were terrible, sent them back as was ridiculous to completely offset the stock Cranks to reach 10-15oz additionally.
Auto’s are even worse with torque converters that take a little bit of centrifugal force to get the Hydraulic fluid equalized across the vanes internally. Anyway- may be able to help more once I have the basic info on the motor.
If you 180*d a Piston i’d expect you to be hearing significant piston slap, as for weight left to right, have had folks bring in motors that they built & installed pistons backwards in both IB and EB motors, result was piston slap varying at around 1,500-3,500RPM’s. No imbalance vibrations noted..
Some aftermarket Pistons were found to be off as much as 6-7 Grams, where a few Pistons replaced, all Rings have given the DIY crowd issues, even after explaining why the shop needs to weight them, they come back when their 50/50 gamble backfires (Pun intended) lol.
A few with bent valves with longer duration Cam’s w/inverted reliefs, more running solid roller Cam’s, not the OHC’s, plenty of room as many had dished or inverted dome Pistons.
Good direction to pull, check, reinstall the Balancer, hope I can help, and it doesn’t need to be R&R’d, torn-down..
Ok, good luck!
Best!
-John
Thanks for the reply. Stock rebuild. It is a 2000 3.8 with 5-speed. I got the car with a locked motor. Took it apart and found out the previous owner had taken the intake manifold off and placed a towel in the valley and when they put the manifold back on they forgot to take the towel out. I dont know how long it ran like that but it was a mess. Most of the towel was around the balancer and pieces throughout the motor. Oil starvation is what locked up the motor. Had the crank ground and put it back together. I'll try replacing the balancer and see if that does anything. Thanks again.
Hi,
Towel- left in the lifter valley?.....good thing he’s not a Surgeon of internal Medicine. This is why alcohol should be restricted to a post job reward. lol!
If the balancer doesn’t clear up the issue, feel free to add to the thread.
Best of luck!
-John