Cylinder head

[Edouard]

Hi all!
I built my FJ and even drove it 50 km (25 miles). But I didn't like the engine or its behavior. Having measured the compression, I got a value of 6 in cylinder 3, in the others 12. Inspection showed that the intake valve was blocked. Before installation, the plane of my head was milled (sharpened). I want to ask, was it possible to do this? And isn't this what caused the bent valve? Most likely the owner in Japan overheated the engine and lost his head

[RPM - Robert]

Did you check the piston to valve clearance before reassembly? If they took so much off the head that the valve would make contact with the piston this is definitely what caused it. A measurement and some thicker or stacked base gaskets would have rectified the issue.

[Edouard]

Did you check the piston to valve clearance before reassembly? If they took so much off the head that the valve would make contact with the piston this is definitely what caused it. A measurement and some thicker or stacked base gaskets would have rectified the issue.

0.2 millimeters were removed from the head of the block. Sorry, I'm using the metric system, the calculator converts this value to 8.7 mils.

[RPM - Robert]

I will ask again, Did you check the piston to valve clearance before final assembly?

Obviously, you aren't the first owner so you don't have the complete history of the bike.

How much was removed is irrelevant. If the head and or barrels was surfaced prior you having the work done then it can still hit the valves.


Were the cams timed correctly, adjustable gears that didn't get tight and slipped causing the valves to be out of time and hit a piston?

[Edouard]

I will ask again, Did you check the piston to valve clearance before final assembly?
Obviously, you aren't the first owner so you don't have the complete history of the bike.
How much was removed is irrelevant. If the head and or barrels was surfaced prior you having the work done then it can still hit the valves.
Were the cams timed correctly, adjustable gears that didn't get tight and slipped causing the valves to be out of time and hit a piston?

When I first assembled the engine, I did not measure the exact valve-piston clearances. The cold engine turned over fine by hand, I checked this. The valves are adjusted to tolerance, all shafts rotate freely, the chain and sprockets are aligned accurately. The compression in the other cylinders is strictly 12. Now I will get a new valve and continue to search for the problem. Although I feel like I've gotten a lot out of my head.
And one more moment. I didn't touch the valves. Perhaps I needed to completely disassemble the head and check all the valves, clean the carbon

[RPM - Robert]

If the valve is bent it hit a piston.

On stock cams you accomplish this two ways, well 3, if it didn't drop a valve spring or broken keeper.

1) piston to valve clearance is incorrect, piston hits valve even when valves are opening at the correct time.

2) timing is incorrect, piston hit valve when it is open and shouldn't be.

3) too much carbon build up on pistons. Which is still number one, piston to valve clearance is incorrect.

Did it drop a valve seat or valve guides leaking? Are you sure it is a bent valve?

[Edouard]

If the valve is bent it hit a piston.

On stock cams you accomplish this two ways, well 3, if it didn't drop a valve spring or broken keeper.

1) piston to valve clearance is incorrect, piston hits valve even when valves are opening at the correct time.

2) timing is incorrect, piston hit valve when it is open and shouldn't be.

3) too much carbon build up on pistons. Which is still number one, piston to valve clearance is incorrect.

Did it drop a valve seat or valve guides leaking? Are you sure it is a bent valve?

I haven't disassembled the valves yet, but the valve is visually intact, but it doesn't fit tightly :-) Yes, there is carbon deposits.