Larry'sGarage

I've been working on my dad's 4.6L windsor motor. He was hearing a "knocking" sound ( we determined was the timing chains) and it lost oil pressure twice, but it went right back up to normal. I have changed the timing chains, tensioners, & guides following a book's directions to keep it in time. I turned it by hand before putting it in the car and it turned a full turn twice. We installed it and tried to crank it, but it wouldn't start. Now it will only turn a half turn in both directions. I'm not sure what I should do. Help.

Old Mustanger

It sounds like the cams are out of time and the pistons are hitting open valves. An OHC engine is a harder one to set cam timing on than an older pushrod engine, so don't feel too bad if you made a mistake.
How many miles are on the engine?
If the engine was not damaged by running low oil pressure (??) it would make sense to replace the oil pump while everything was apart.
The loss of oil pressure could be caused by a bad sending unit. If I remember correctly, the oil gauge in your car is an idiot gauge, it doesn't really read accurate oil pressure. It just operates like an idiot gauge.

Larry'sGarage

Thanks. I'm gonna go double check my timing.

uberstang1

Double check , don't wanna damage a piston or bend a valve.

Larry'sGarage

Thanks guys. I checked I was timed right, but I took the head off and found a bent valve. It had been bent for a while as you could see where the it was burnt past the seat. Thanks for the input.

Old Mustanger

If you originally had a bent valve, you should have seen more symptoms than you had.
The cylinder would have been dead so it would have run pretty rough. Plus there would have been a popping sound out the exhaust or intake.
Valves don't bend for no reason, could something have fallen in the intake? Is there also a hole in the piston?
Did your dad have any recent work done on the engine before the knock developed?

caaraa

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uberstang1

Yes I highly doubt the valve was bent prior to this, something went wrong with the head install.

Larry'sGarage

It had been running kind of rough & would quit occassionally for no reason, but he said it ran better on top end. I never personally drove it, just took his word for it. It did have a very strong exhaust smell. He said it would burn his eyes if he had to sit in traffic or at a drive-thru very long. Other than a "knock" and it losing oil pressure a couple of times, he said it was fine. He hadn't had any work done previously & I didn;t remove the heads when I did the timing work. One piston has an indention & is gummed up real bad. The driver's side head is fine and the pistons look good too. I appreciate the help.

Old Mustanger

There is something seriously wrong with that engine. Did your dad say that he had NOT had any work done on the engine recently? That is hard to believe, unless something loosened up internally and finally let go. But that would be an almost impossible coincidence.

You should seriously consider purchasing a used engine. With chunks of something bouncing around in one of your cylinders, you most likely will have to buy another head, plus rebuild the whole engine.
With those problems plus your dad's claim of lost oil pressure, I would consider that engine a goner.