In This Article:
The head bolt holes are cleaned with a 7/16" tap. The head gaskets are laid on the engine block and the cylinder heads set in place. The head bolts are installed and torqued. The pushrod and rockers are installed.
2 - 3 Hours
Bruce W. Maki, Editor
Before the cylinder heads can be installed, the engine block and head mating surfaces must be perfectly clean. All traces of oil and dirt must be removed or else the head gaskets may develop a coolant leak, or worse, leakage of the high-pressure gases from inside the cylinders.
Escaping combustion gases (essentially exhaust) can actually erode away the metal of the engine block and/or cylinder head, and ruin the engine.
I used a 7/16 inch coarse tap (14 threads per inch) to chase the cylinder head bolt holes in the engine block. I sprayed a few drops of brake cleaner into the holes while turning the tap, to lubricate the cutting teeth. Then I cleaned the gunk off the tap with compressed air, and sprayed some brake cleaner into the hole.
I suppose this procedure should have been done when I was cleaning the engine block, but I didn't have the right size tap at the time. There is a risk of getting some junk into the cylinders, so I was extra careful.
After cleaning the cylinder head, I wiped the mating surface with a clean paper towel sprayed with brake cleaner. I wiped the head and engine block deck repeatedly, folding the towel to get a clean section four or five times, until the paper towel picked up no dirt or oil. Then I used a lens cleaning cloth to wipe the surfaces. These cloths (paper, actually) contain isopropyl alcohol, and leave no residue.
Since the 1990's, GM has been using Torque-To-Yield head bolts on their engines.
Torque-To-Yield (TTY) bolts actually become permanently stretched after they have been tightened properly, and General Motors (and every decent mechanic) advise against re-using old head bolts. These bolts aren't expensive... I paid about 24 bucks for two sets of aftermarket head bolts.
Some older GM V6 and V8 engines may not use torque-to-yield head bolts. Most auto parts stores should be able to tell you if your particular model year requires TTY head bolts or not.
I set the new head gasket in place.
The left and right-hand cylinder heads use the same gasket, and at first these gaskets appear to be reversible. But on closer inspection, I noticed some minor differences between sides. Also, the holes that fit over the guide pins are not the same... the left-hand hole is triangular shaped while the right-hand hole is round. (The original gasket had the same feature.)
I carefully set the cylinder head onto the engine block, being careful to avoid touching the mating surfaces with my fingers.
I threaded the first bolt into its hole to prevent the head from falling off the block. Dropping a cylinder head on the floor would really suck!
I applied a dab of oil on the underside of the head for the long and medium bolts.
It's important that the bolts turn freely and have no sources of friction besides the bolt threads, to avoid any error while applying the proper torque.
On the short bolts, which lie close to the exhaust manifold, I applied some copper-based anti-sieze compound to the underside of the bolt heads.
Note the white stuff on the ends of the bolts. All of these bolts came with thread sealant already applied.
If you were installing cylinder heads on an engine with reusable head bolts, you would need to apply some thread sealant to the bolt threads, because many head bolts go into the water jackets of the engine block, and a coolant leak would result if the threads were not sealed.
First I installed all the bolts in the proper positions and threaded them snug. Then I set my torque wrench to 22 foot-pounds and tightened each bolt in the required sequence, which basically starts in the middle and works outward in a somewhat circular fashion.
Head bolt tightening sequence for the right-hand (driver's side) cylinder head.
After tightening to 22 foot-pounds, each bolt has to be turned a certain number of degrees:
Instead of tightening the bolts in one pass, I first turned each bolt 30 degrees, following the specified pattern.
Then I went back and turned each bolt the additional amount (25, 35 or 45 degrees) required.
After cleaning the pushrods in xylene (I scrubbed them with a brass brush), I dipped the ends in assembly lube.
I made sure to keep track of the top and bottom end of each pushrod... the rods must be placed in the exact order and orientation as when I removed them.
I inserted each pushrod into its proper hole in the cylinder head.
When cleaning the rockers, I made sure this little oil hole was not plugged.
This is important, because this hole aligns with the hole in the end of the pushrod as the valve train moves, letting a bit of oil squirt out to lubricate the valve area.
After cleaning each rocker in xylene and blowing off the solvent with compressed air, I applied a dab of assembly lube to the points where the rocker presses against the pushrod and valve.
I used a disposable foam brush to apply lube. I placed the rocker on the rocker stud.
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I cleaned the pivot ball and applied some assembly lube on the underside.
I set the rocker arm in place on the rocker stud.
Then I set the pivot ball over the stud and installed the nut. I tightened each nut to 20 foot-pounds.