900SAAB.com: Short Block Assembly

Engine Overhaul: Short Block Assembly

To begin engine assembly, the short block was assembled. To demonstrate this in a stepwise fashion, the balance-shaft plugs were installed, followed by the balance shafts. The piston cooling jet, main bearings, crankshaft and pistons/rods were installed next. Finally, the rear timing cover was installed.

After the block has been cleaned, reconditioned, machined and cleaned again, it's time to begin assembly. The balance shafts should be installed first. To ensure that the balance shafts were flawlessly clean, I made a brush using some PVC pipe, a terry cloth towel and electrical tape. I then srubbed the balance shaft bores with mineral spirits. While this brush looks rather phallic, it worked well!

With the bores clean and dry, I lubricated the bearing surfaces of the balance shaft using Lubriplate 105 and slid them into place. The balance shaft marked exh is installed on the exhaust side, while the balance shaft marked inl is installed on the intake side. The bolts were installed using loctite blue.

Next, the main bearings and crankshaft were installed. The main bearing surfaces were wiped with lacquer thinner and the main bearings were installed, with great care being used to ensure that each bearing was aligned perfectly.

The crankshaft was laid into place and plastigage was placed on each main journal; the main caps were installed and torqued to spec. The main caps were removed and the clearances noted. On my crankshaft, the main journals averaged 0.036 mm clearance.

The plastigage was carefully removed with lacquer thinner and the bearing journals were lubricated using engine assembly lube.

The main caps were fitted and torqued to 81 ft lbs using an E-16 external torx socket. I am using a Craftsman 1/2" click-type torque wrench to install all bearings.

With the crankshaft fitted, the pistons/rods were installed next. In preparation, the bearing surfaces were cleaned with lacquer thinner, the rod bolts were protected with vacuum hose and the rings were soaked in oil.

A band-type ring compressor was used to compress the rings and the piston assembly was tapped into the block. Plastigage was placed on the journal and the rod-caps were torqued to spec. The average clearance of the rod bearings was 0.026 mm.

Finally, the engine was supported using the shop crane and the rear cover was fitted. Anaerobic sealant was used on the gasket surface. All bolts were installed finger tight and then torqued, in a criss-cross fashion, to 12 ft-lbs. Here is the assembled short block.

A word about ring compressors: DO NOT BUY OEM INDUSTRIAL ring compressors (sold by Advance Auto Parts and Checker/Kragen/Schucks); they utilize thin bands and a poor locking mechanism and will wedge themselves in between the piston skirt and the cylinder wall when you attempt to tap the piston into place. This happened to me, while installing the #2 piston, and put a sizeable gouge in the piston skirt. I've decided to replace the piston with a new SAAB AB piston (the tune of $375, yikes!). This happened to the first piston I chose to install; afterward, I purchased a Craftsman ring compressor (for $8; $2 cheaper than the OEM Industrial) and it's worked like a champ.

Here is a shot of the damage to the piston:

While this damage does not look significant enough to warrant replacement, given the tight clearances between the AB pistons and the B bores, I chose to replace it as it would cost me more than $375 to tear the engine back apart to replace a seized piston.

So, I'm waiting on a replacement 2.3 NA AB piston (9149360) from SAAB. This will hold up assembly of the engine. Since I now have some downtime, I took this time to clean and prepare the engine bay. For the initial cleaning I sprayed each underhood component with a safe aerosol engine degreaser and wiped the surface clean with a microfibre cloth. Here are the results of initial cleaning.

The next step is to wash down each item in the bay, again, with dishsoap and water and then apply a protectant to all underhood hoses and plastic. For plastic/rubber protectant, I use Black Magic's Engine Detailer. It's a silicone based product and will clean/protect the underhood plastics.

This is the engine bay after a second cleaning and application of detailer.

With the short block assembled, I moved toward installation of the balance and timing chains. To renew this system, the both chains, both tensioners, all sprockets and all guides were replaced. Here is the balance shaft chain, as installed.

Before the timing chain is installed completely, the cylinder head will be installed. This will allow me to ensure that I have the camshaft timing correct before installing the timing cover or oil pan.