So my motor is out of my 1985 fj60. It was daily driven and has around 500k. It is now in my 1968 fj40. I was having some fuel delivery issues during an event at GSMTR2023. So I parked up on the trailer. So I went to take it off the trailer Monday as I hit the key and the motor was turning over I hear a metallic nut dropping sound followed by a thunk. Now the motor has a dead spot. So to explain I stoped trying to crank it. And put a ratchet on it on the main 46mm nut. You can rotate it 180 and then the motor stops. Then rotate it back 180 and stops again. I disconnected the starter to make sure it was not disengaging and locking the flywheel. Then I pulled the plugs and other than the motor running rich normal. I did not inspect the top of the piston just yet. I then checked the oil with the dip stick and it was perfect not low or high and looked good. I check the coolant same story. I dropped the oil pan and it was spotless no chunks or pieces found. Now I need to use a magnet in the drained oil have not done that. So next I’m going to remove the rocker arm assembly. And see if the motor still has a dead spot.
1968 Fj40 locked up when starting. (1 Viewer)
- Thread starter Slow85
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Dropped a valve? Could check your clearances - maybe one is zero
I'd look at the cam gear. Had a 235 Chevy that did that. Good luck.
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Update so I looked at the top of the pistons some are oily so are dry no damage. I took the rocker arm assembly off and still no change. The motor is locked up and will only rotate 180 in either direction. I pulled the push rods all look normal. So the only visible thing is the Exhaust port on cylinder #4 is higher than all the rest!
That would typically indicate a burnt valve and/or seat. But you have additional issues. Perhaps the end broke off and it's stuck in the piston blocking the cylinder from rotating fully. Do you have access to a bore scope?
pb4ugo
SILVER Star
I was thinking a broken valve too.
Did you use a bore scope? You're only getting 360* of rotation. Like something is sitting on top of the piston and stops rotation when the piston is at the top of the stroke, or the cranks timing gears chipped, which I doubt.
Did you use a bore scope? You're only getting 360* of rotation. Like something is sitting on top of the piston and stops rotation when the piston is at the top of the stroke, or the cranks timing gears chipped, which I doubt.
Always nice when you guess right first time
Sounds like the valve head came off. Surprised you can't see it on top of the piston if you have an endoscope.
May as well take the head off.
Hope it didn't do too much damage - looks like it's time for a head rebuild.
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I don’t have a bite scope tho I have always wanted one. I monger be able to narrow one
no I don’t have one but I have always wanted one! I think I have access to one thru a friend I’m checking.
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- #10
Timing gear is an option as well have you ever seen where that has happened.
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- #11
Well it is always nice to be right the first time. I have not check the clearances on the valves I was looking thru my FSM but remember reading somewhere you needed to start at TDC and check exhaust1, 5 and 9 and intake of 2,3 and 7 then rotate 360 and check the others. But I can’t rotate a full 360 only 120 and 120 it seems like.Always nice when you guess right first time
Sounds like the valve head came off. Surprised you can't see it on top of the piston if you have an endoscope.
May as well take the head off.
Hope it didn't do too much damage - looks like it's time for a head rebuild.
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Always nice when you guess right first time
Sounds like the valve head came off. Surprised you can't see it on top of the piston if you have an endoscope.
May as well take the head off.
Hope it didn't do too much damage - looks like it's time for a head rebuild.
He has the rocker arm assembly completely removed - this would bring all the valve stems to the highest point. I would think the combustion chamber on his flat-top piston 60 engine would be big enough to allow it to still turn over with a loose valve head in the cylinder.
They should all be at the same highest point though with all the valves seated.
The fact that exhaust 4 is half an inch above the others tells me that either the valve head or the seat is no longer where it should be. The former being the most likely to have parted company with the valve stem.
It's most likely wedged in the top of the soft piston rather than the iron head.
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I didn't notice that valve sitting higher in that pic, but you're right. Bummer!
Do you stock pistons and valves for that motor?
We had a similar problem on our car when I was a kid - my dad brazed a 2 pence coin over the hole in the piston and it ran fine for years. I wouldn't recommend that approach though.
Whatever you end up going with replacement wise, if you pull the head, post up some pics. I'm sure we all are curious to see what lurking in there.
That’ll do it. We should have guessed seat when one spring was taller but not loose.
Wow, seat disintegrated after all, you did say that you had some fueling issues prior - maybe it was running a bit lean for too long?
How do the other exhaust seats look, and any damage to the bore?
How do the other exhaust seats look, and any damage to the bore?
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