1996 Toyota Previa 1996 Toyota Previa SC knocking after hea

I will test it and get back to you.

If everything is fine and the van runs normal, I guarantee the noise that you're hearing is from the cam sprockets. I believe you had skipped one important step in reinstalling the camshafts during your cyl. Head job process.
On the exhaust cam, it has split gear, before you remove the cam, you must lock down the SPIT GEAR before removing it.

Solution:
1. You remove both cams (again) and everything everything else that's involve-you may need to one motor mount to get to the chain tensioner. You can just lose the intake cam and leave in the spot just enough to remove the exhaust cam.
2. Remove the exhaust cam and lockdown the split gear by:
a)set the cam on a vise, turn the outside gear clockwise as until the hole are line up and lock it down with 10mm bolt.
3. Reinstall both cams, then remove the 10mm bolt from exhaust cam and put everything back.

This process should take about 1-5 to 2 hrs.

Good luck

Samay, the previa guy from Seattle.