Crankshafts vs. Impact Wrenches

[Mike T.]

We just replaced the timing gears and chain on our 72 350, and also installed a new harmonic balancer.
We started it up, and it knocks and has no oil pressure.
The motor had no problems before the work, other than the fact it got poor gas milage. We thought the timing gear/chain were worn because we couldn't get the motor to "ping" no matter how far advanced we moved the distributor.
The manual stated 80 ft. lbs. on the bolt fastening the harmonic balancer to the crankshaft. We used an impact with the air compressor at 80 pounds. We barely touched the bolt because we had tightened it manually pretty tight but the motor turned and we couldn't get it to 80 lbs.
Did we ruin the main bearings by somehow causing the crankshaft to move?
The only other thing I can think of is that we just lowered the front of the oil pan when taking the timing cover off. Maybe somehow the angle of the pan caused the oil pump pickup tube to fall out of the pump.
Thanks for your help.

[Joe L.]

Re: Crankshafts vs. Impact Wrenches

We just replaced the timing gears and chain on our 72 350, and also installed a new harmonic balancer.
We started it up, and it knocks and has no oil pressure.
The motor had no problems before the work, other than the fact it got poor gas milage. We thought the timing gear/chain were worn because we couldn't get the motor to "ping" no matter how far advanced we moved the distributor.
The manual stated 80 ft. lbs. on the bolt fastening the harmonic balancer to the crankshaft. We used an impact with the air compressor at 80 pounds. We barely touched the bolt because we had tightened it manually pretty tight but the motor turned and we couldn't get it to 80 lbs.
Did we ruin the main bearings by somehow causing the crankshaft to move?
The only other thing I can think of is that we just lowered the front of the oil pan when taking the timing cover off. Maybe somehow the angle of the pan caused the oil pump pickup tube to fall out of the pump.
Thanks for your help.

Mike------

Well, considering what you did, I cannot see any reason that an oil pressure problem should be created, especially since you never even removed the oil pan or removed the oil pump. Removing the balancer, removing the timing cover, replacing the timing set, and re-installing the cover and balancer should have no affect on anything related to oil pressure. I can't even imagine that anthing related to oil pressure was even disturbed.

As far as the balancer bolt goes, I would not have installed it with an impact wrench (removing one with an impact wrench is OK, but I wouldn't use one to re-install it). However, did you use the balancer bolt to draw the balancer onto the crankshaft? Some folks do this (and with an impact wrench), but I don't. The best way is to use a balancer installation tool to draw the balancer onto the crankshaft, then install the balancer bolt and torque to spec with a torque wrench.

In any event, even if you did use the balancer bolt with the impact wrench to install the balancer, I can't see why that would subsequently cause any problem with oil pressure. Also, be advised that using an impact wrench with 80 PSI air pressure does not mean that you are applying 80 lb/ft of torque to the bolt. You are actually applying far more if the impact gun has any significant rating. However, I still don't see how this would have any effect on oil pressure-------you might break a bolt or strip out the threads in the crank, but that's about it.

So, what's causing the oil pressure problem (and, by the way, you definitely have a REAL oil pressure problem if the engine is knocking)? There must be more to this story than you've reported. In other words, something else that was done that may have seemed trivial or which you've forgotten. Did you, perhaps, drain the oil from the engine prior to doing this job and forget to re-fill the crankcase?

I see very little chance that you disturbed the oil pick-up by lowering the pan slightly. The oil pick-up screen is a press fit in the pump and, if installed correctly, will not be affected by anything you could have done.

[Mike T.]

Re: Crankshafts vs. Impact Wrenches

Thanks Joe. That's reassuring. Thought I had ruined something with that impact wrench.
I'm gonna borrow a tool for my drill and spin the oil pump. If I get pressure I'll be sure the pickup tube and bearings are OK.
Then I'll start looking at the distributor/oil pump connection.

[Mike T.]

Re: Crankshafts vs. Impact Wrenches

Happy ending!
I took the oil filter off, (it was brand new because I did an oil change at the same time). I usually fill it up with new oil before I install them, but this time I only had it 1/2 full. I filled it to the top, and reinstalled it.
I then pulled the coil wire, and turned the motor over. It said "0" oil pressure, and I kept cranking it for about 10-15 seconds. Finally, the gauge needle popped up and we were in business.
I reconnected the coil wire, and it runs perfect!
For some reason, something lost prime.
Thanks again Joe! Time to celebrate!

[Thomas H.]

Re: Crankshafts vs. Impact Wrenches

Don't forget to go back and verify the torque on the balancer bolt.

Tom