Do i need to reset timing when installing a replacement head?

[slowpoke]

73 240z

automatic

e88 head

The head on my 73 is most likely warped or cracked. I bought it this way. Tried to replace the head gasket and it still leaks coolant into a cylinder. I ordered a complete head from a parts yard, that i intend on replacing my damaged on with. My question is: can i replace the head in the same manner that i removed the previous one (wedging the chain at TDC) ? Or do i have to remove the front cover and start over with setting the timing?

[Zed Head]

If you set your timing mark to zero on the compression stroke and the cam sprocket notch is lined up with the oblong groove as shown the Engine Mechanical chapter, BEFORE you take everything apart, you should be able to align the notch with the groove on the replacement head before you install it and everything should drop in to place and be correct. Those are the two pairs of things that need to match - damper pulley notch with zero, and oblong groove with sprocket notch. Get everything aligned and the chain in place before removing the chain tensioner holding block, and don't turn anything until those are aligned.

[Jeff G 78]

Make sure the "new" head is flat and full thickness prior to installing it. Put it on a known flat surface and use feeler gauges to see if there are any gaps. If it isn't flat, get a refund. Then measure the overall thickness of the head with dial calipers. It should be 108mm and if it measures less, it has likely been milled. A milled head will cause a change in timing, so if it has been milled, you might need to use the #2 or #3 hole in the cam gear.

[Zed Head]

Jeff G knows more than I do about this stuff and raises some good points. In addition, you, the OP, didn't say if you were getting a complete head with the camshaft still installed or a bare head, or a head with vlaves and springs but no camshaft/rockers. If you're swapping cam and rockers, there are more things to consider. Lots of knowledge on the forum, describe what the salvage yard is sending you.

Also, I overlooked that you have already removed and replaced the original head. It should be the same process, if notch and groove are lined up.

[slowpoke]

Thanks for the advice so far.

I asked the yard if i could get a refund if it is warped or cracked, they said yes. I defiantly plan on checking it to see if is warped as i could have saved myself some time and grief if i had done so when i first replaced the HG. So it sounds as though the answer to my question is yes, I can replace my head with a "new" head by keeping my engine in time during the swap so long as the replacement head has not been previously milled. The yard said the replacement head was complete with rockers and cam. Also my cam gear is already on the #3 position (i know i should replace the chain, this will happen during the winter, during a more complete tear-down), so if this is the case i will return the head and search for an un-milled one.

[slowpoke]

Also are new head bolts necessary?

[Jeff G 78]

No, you can reuse the old ones. Just make sure the block and bolt threads are clean and free of sludge and rust.