08-05-2019, 05:06 AM
Hi zirconxi,
Here are some opinions on your questions 1-4 (#5 answered in Post #2 by max).
1.) The cylinder head is cast with the lower cam bearing holders in the head, but the upper cam caps are separate castings. All will have the half-moon space for the camshaft bearings, but they need to be finish machined through a process called line boring.
Camshaft bearings needed to be located precisely, so they will always have hollow dowel pins to keep them from squirming when bolted down.
The un-machined cam bearings are torqued down to spec with their dowel pins, and the cylinder head is securely held down.
Then the long, precisely located, spinning boring bar, with multiple cutting heads for each cam bearing, can pass through, into a rigid support bearing on the other end. (That is also the reason the cylinder heads have those half-moon cutaways on the outer surfaces on both sides.
So each of those cam caps are precisely matched to the bearing in the head, and they must be kept in the exact location, which is why they are numbered/lettered, or otherwise located.
2.) I would torque them all to spec.
3.) If the camshaft/bucket clearances are within spec, I would not be worried. Valve clearances are likely to get tighter as the valve head pounds into the seat. There is likely no wear on the camshaft or cam bearing holders, as long as there is oil pressure.
I would run the recommended 10w-30 oil, maybe change it more often. The thicker 15w-50 will not flow as well, and will make the engine run hotter.
4.) The cam cap threads can be repaired with a Heli-coil or Time-sert or other steel thread insert. But no, having it looser than the torque spec will not affect anything unless there is oil loss.
Here are some opinions on your questions 1-4 (#5 answered in Post #2 by max).
1.) The cylinder head is cast with the lower cam bearing holders in the head, but the upper cam caps are separate castings. All will have the half-moon space for the camshaft bearings, but they need to be finish machined through a process called line boring.
Camshaft bearings needed to be located precisely, so they will always have hollow dowel pins to keep them from squirming when bolted down.
The un-machined cam bearings are torqued down to spec with their dowel pins, and the cylinder head is securely held down.
Then the long, precisely located, spinning boring bar, with multiple cutting heads for each cam bearing, can pass through, into a rigid support bearing on the other end. (That is also the reason the cylinder heads have those half-moon cutaways on the outer surfaces on both sides.
So each of those cam caps are precisely matched to the bearing in the head, and they must be kept in the exact location, which is why they are numbered/lettered, or otherwise located.
2.) I would torque them all to spec.
3.) If the camshaft/bucket clearances are within spec, I would not be worried. Valve clearances are likely to get tighter as the valve head pounds into the seat. There is likely no wear on the camshaft or cam bearing holders, as long as there is oil pressure.
I would run the recommended 10w-30 oil, maybe change it more often. The thicker 15w-50 will not flow as well, and will make the engine run hotter.
4.) The cam cap threads can be repaired with a Heli-coil or Time-sert or other steel thread insert. But no, having it looser than the torque spec will not affect anything unless there is oil loss.