QuestionI removed the head from my 1985 pickup 22R engine. Examining the gasket it looked like compression gases were traveling from the number 1 and number 4 cylinders and into the coolant. Small groves were forming in the gasket between the cylinders and the cooling jacket. The engine had classic head gasket leak symptoms; an over-pressurized cooling system, an erratic temperature guage, and the heater core filling with steam. There was no water in the oil.
A machinist's straight edge showed the head was .003 warped. The machinist recommended resurfacing the head to get rid of some corrosion and slight depressions where the gasket fire rings rubber into the aluminum head. The work was done right and I am getting ready to install the head.
I have serveral doubts about the process. Because the head was slightly warped and now it has been milled flat again. I haven't seen anyone worry out loud about this, but it sure seems that now the warp remains in the body of the head, but with the bottom flat again. The concern is that it appears like the cam will now be turning within its bearings in a .003 arch across its entire length. In the machining process do they straighten the head before they are milled flat or does the warp now remain in the cam and the bearing alignment? Should I have the cam bearing surfaces line bored or have bearing inserts installed?
In an associated problem should I use some kind of gasket sealer or any substance on the gasket and head and block surfaces before I torque down the head.
Also, while I am at it here, when I first removed the valve cover I turned the crank to TDC, right on 0. And both number 1 valve rockers were loose. In this condition I noted that the timing dimple on the cam sprocket was located about, I estimate, 10 degrees before the timing arrow mark on the forward cast rocker arm support. Is this where the cam should be or is it possible that somewhere in the history of this machine that the timing chain was installed one tooth off? Or is this apparent 10 degree early cam timing normal and the engine corrects the problem when the engine starts and oil pressure activates the timing chain tensioner? Or am I misunderstanding the the cam timing? Andrew, thank you for your patience and wisdom.
AnswerHi there,
Toyota specifications allows no more than .010 of clearance in regard to a warped head that needs resurfacing. Anything above that, toyota recommends that it be replaced. You are well within the limits of this requirement. The small warp you are concerned about that might remain is a non issue because after you torque the head in proper sequence, in essence, will warp the head to a degree. Hence, one of the needs for a head gasket. I would not have the cam journals bored at all. The machine shop should have assembled the head for you (valves, springs...etc). You do not need to have any type of sealer for the head prior to installation. Just make sure the surfaces are clean and free of any debris or rust (not knowing how long the head has been off). Obviously, I cannot tell you the history of your truck and how the timing chain was installed by someone else. I would set the engine back to factory specifications when re-installing the timing chain.
