Tip & How-To about Toyota Pickup
75-94 Toyota 20-21-22R Corona Celica Pickup, Four Runner.
These last a long time, there are lots of them still running, blowing head gaskets, warping heads, and we keep sending them off to be surfaced. One thing that is often missed is if the top surface is flat, if it isn't the cam will rock, if just a little the valve adjust will never be right and it will always make excessive valve train noise, if a lot, it will either break the cam, or seize it. Some machine shops that specialize in these engines have jigs to hold the head flat while the head is surfaced, most don't. We have found that if we take some soft 8th inch aluminum and make two inch wide pieces with notches or holes for the aligning pins, lay them on the block one front, one back, and blot the head down with the center six bolts, carefully, evenly until the head starts to flex, and leave it a while, a few hours, then tighten a little more, until it is just the other side of flat, keep the straight edge close, it needs to be within .004" or so. loosen it up and check, if it needs more, just tighten it down again, a little at a time and evenly among the six bolts, an easy way to tell if it's right is to have the cam in but no cam caps, then use the rocker assembly right on top, as you tighten feel the cam, when it stops rocking and spins free you are there, the cam journals are what we are most concerned about.
I have not had one fail, (yet), I would not do this on a turbo head as they are usually a different alloy and more subject to cracking.
Of course watch out for overheating that got hot enough to anneal the head, if so it will dent easily, a push type center punch works good, they have a consistent punch, do a few on it, then on a known good one, if they are larger, it has gotten soft, don't use it. Look also for electrolysis, if there is any visible in the coolant ports of the head, there will be more you can't see, don't use it if you or someone else is depending on it.
Hope this has helped
Sometimes fixing vs replacing makes the difference between making a job work, and it not being economically feasable.
Posted by reson2 on
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