In This Article:
The exhaust manifolds are removed. The rocker arms and pushrods are removed and stored in order. The head bolts are removed and the heads lifted off the engine block.
About 2 Hours
Bruce W. Maki, Editor
Just getting to the point where I was able to rebuild this engine meant removing the engine from the car and setting it on an engine stand. That took about 4 solid days of work, mostly with a helper who was quite experienced with working on cars.
Before placing the engine on the engine stand, I would recommend removing the nut and stud (red arrow) on the rear oil seal to the back of the engine block. The stud has a small hex on the end, but I don't know what size it is. (Probably metric, 6mm or smaller.)
Removing the stud should be done with an impact wrench to reduce the chance of breaking the thin stud.
I say this because it might not be possible to remove the stud once the engine is mounted on the stand, and removing this stud makes it possible to install a new rear seal when the crankshaft is installed, rather than waiting until just before the engine is installed.
I removed the exhaust manifold bolts with an impact wrench and a 14mm socket. (A 9/16" socket may fit.)
I originally figured that I would need to use a torch to heat the bolts and break the corrosion that is common on exhaust system fasteners. I had heard horror stories about removing exhaust manifolds... about how easily the bolts or studs break, and the need to drill out the broken bolt shaft stuck in the cylinder head.
But I decided to simply try removing the bolts with the impact wrench, just to see what would happen. I figured the impact wrench would just hammer away and the bolt wouldn't move.
Well... the bolts came right out. Heck, they practically fell out. I'm guessing that General Motors put some anti-sieze compound on those bolt threads.
The right hand side after the exhaust manifold had been removed.
I still needed to remove the metal bracket at the top of the cylinder head.
The left side showing the dipstick tube.
To remove this tube, I had to drop the oil pan first, and then tap on the lower end of the tube with a hammer and a block of wood.
The oil pan is secured with 10 bolts and 2 nuts.
When I started working on this engine, I was eager to check out the connecting rods to see if there were any obvious signs of trouble. I had never fixed a rod knock before, and I was curious to see if any of the connecting rods showed any looseness.
When I turned the engine upside-down, I expected some oil to drip out. But I was surprised by how much coolant spilled out.
I would suggest placing a large tray or catch-basin under the engine when turning it upside-down for the first time. Later, I found one of those big plastic storage containers that fit under a bed. The lid was broken so I re-purposed it for garage use. It made a good drip pan.
On a GM 350 cubic inch V8 engine, the oil filter would go here.
But the Jimmy and Blazer have so little room beneath the engine that General Motors decided to run oil lines to the front of the car and place the oil filter under the radiator.
This hole should be kept covered to prevent dirt and junk from getting into the oil passageways.
I simply folded up a clean paper towel and stuffed it in the hole.
Perhaps an even better idea would be to just re-install the oil filter adapter.
To turn over the crankshaft, I placed the 3 pulley bolts in the harmonic balancer and used a large prybar to turn the crankshaft.
It's probably easier to just install the snout bolt (which is removed when the crankshaft pulley is removed) in the end of the crank, and then use a deep well socket and a breaker bar to turn the engine.
I turned the crankshaft so each piston was at Top Dead Center (TDC), starting with cylinder number 1.
I used a 1/2 inch socket to remove the nut on each rocker arm.
To keep track of the rocker arms, I used a piece of cardboard with holes punched in it.
I placed a cable tie through the rocker, nut, and ball, then I pushed the end of the cable tie through the cardboard and looped it around to connect it.
I removed the pushrods and placed them in holes punched into a cardboard box.
I wrote on a piece of duct tape on the box to mark the front of the engine.
This will keep the pushrods in proper order so everything can be installed in the original positions.
I removed the hang hook. It may be difficult to remove the right cylinder head with the hang hook in place.
The ends of these studs (red arrow) have a small hex, which fits a 1/4 inch socket. I used a 1/4 inch socket adapted up to the 1/2 inch square drive of my impact wrench to remove these studs.
The head bolts MUST be removed in the proper sequence, or else there is a risk that the head can warp.
I removed the head bolts in the proper order (the opposite of the tightening sequence), which is basically from the outer edges toward the center.
Some service manuals say that head bolts should be removed by loosening the bolts only 1/4 or 1/2 turn at a time, in the proper sequence, until the bolts are loose.
That careful procedure could take a long time. I've never seen a mechanic remove head bolts in tiny increments... they'd never make any money working so slow.
I used an impact wrench to do most of the disassembly on this engine, and I experienced no problems once the engine was rebuilt.
I marked up this picture to illustrate the head bolt removal sequence.
This photo shows the right-hand (driver's side) cylinder head.
My service manuals basically imply that the removal sequence for the left-hand head is the mirror-image of the pattern shown above, but since the heads appear to be identical, I suppose it might be better if you used the exact same sequence and disregarded the "Front of Engine" note.
With the sequence shown above, the last bolt removed (13) is in the middle row between the two exhaust ports that are farthest apart.
After I removed the head bolts, I pried up the cylinder heads and lifted them off the engine block.
Getting the head to separate from the engine block wasn't easy. I used a thick putty knife with a tapered end and hammered it into the gap between the head and the engine block. I did this at the rear outer corner of each head, and I drove the putty knife in just enough to break the seal formed by the head gasket.
Then I used a pry bar to carefully lift the head and completely separate the gasket from the engine block.
Note that there are two guide pins used on each head, to align the head with the engine block. These pins will keep the head from sliding off the block until the head is lifted up about 1/4 inch. To be safe, it might be a good idea to thread one head bolt part way into a hole to make sure the head doesn't go anywhere until you are ready.
Be careful at this point. It's possible to drop the cylinder head on the floor, which could ruin the head.
I placed each cylinder head on the floor, on a piece of cardboard to prevent damage. Storing the cylinder head off the floor would be better, such as on a shelf or workbench.
Build A Basic Workbench (From HammerZone.com)
The left bank of cylinders.
Note the slight amount of rust on the walls of cylinder number 6 (at the left of the picture).
Hopefully this won't be a problem.
I believe the head gaskets on a Blazer or Jimmy can be replaced while the engine is still in the vehicle, but I haven't done that repair job.
The intake manifold would need to be removed, as shown in this article, which is not a difficult job.
The exhaust manifolds would also need to be removed. I doubt the exhaust manifolds could be pushed aside far enough to allow access to the lower row of head bolts. Removing the exhaust manifolds requires removing the nuts that connect the exhaust "Y" pipe to the manifolds. I was able to remove these nuts with an impact wrench and some long "wobble" extensions. I would recommend using a wire brush to remove some of the rust on the 3 studs between each manifold and the Y-pipe, and then applying some lubricant to the stud threads so the nuts don't "gall" the metal and stick, causing the studs to break.
I bought an "upper" set of gaskets for this engine (Victor-Rienz), which includes the head gaskets, intake manifold gaskets, exhaust manifold gaskets, and more, for about $50. It may be wise to buy new exhaust manifold "donut" gaskets as well.
The engine block "deck" will need to be cleaned up, as well as the cylinder head mating surfaces, as shown in these articles: