i have read that the later heads on the 4zd1/4ze1 are "better" and that they are less prone to cracking. how can you tell the difference? is there different stamping? is there a certain year to look for?

yes, there is a casting number... let me see if I can remember this right. castings 1,2,3 are the earlier weak ones. 4,5 are the later strong ones. but I seem to remember jerry telling me that the years after 5, they reused some of the earlier numbers with some additional marks (there is no 6, but there were castings done after 5).

-Rob

It is better to know what vehicle they came off of. Early heads from 88, maybe early 89 with low numbers are generally considered to be problem castings. Rob is right, they numbered them 1-5 and started over after 5.

Frankly, with the age of the vehicles out there, I would strongly suggest an AMC head. By the time you get a head, have it worked through, you will be pretty close to what an AMC casting would cost. But, you will still have a 20 year old head that has been re-worked.

Or go for a smaller combustion chambered head from 93+ and enjoy the compression bump.

Michael

I agree, I would go with a later casting if you want to have an oem head. I wouldn't go with anything older than a number 4.

The casting number is located on the rear of the head, pressed up close to the firewall. Its impossible to see it with the head on the block in the engine bay. The best you can do is feel it with your fingers, and look for a grease imprint. Reach in from the driver's side.

That being said, I replaced a number 4 which had several cracks and bad valves (see photos below). I went with an AMC head, and have no regrets.

You don't need to read Braile... just use this http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200303701_200303701