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Pontiac shortblock assembly
Thursday, September 24, 2020
written by Lee Atkinson

Initial block prepartion

Before any assembly begins, the block needs to be as clean as reasonably possible. Start by performing any die-grinder or file work (optional). This includes rounding over sharp edges left from machining (to eliminate sharp edges that can cut skin or scrape engine parts, and also be possible starting places for cracks), removing casting flash, and polishing oil drain paths in the lifter valley. Any other process that could MAKE the block dirtier should be done at this time. Note that some of these operations CAN be done before you take your block to the machine shop.

Next comes "chasing" (using a thread "tap") all the bolt holes (head and main, at least), and threading any other holes that are to be threaded. This will eliminate the largest of the pieces of debris. Blow out each hole with compressed air, or spray carburetor cleaner. If the block is on an engine stand, it can be rotated so that the hole being chased is pointing downward, as this will aid in assuring all metal shavings fall out of the hole. At this time, any obvious dirt, debris, metal shavings, or other contaminants should be cleaned off of the block.

You are now ready to clean out the oil galley passages (optional, but HIGHLY recommended). For this task, you will need either a set of long engine cleaning brushes, or a set of rifle cleaning brushes. Start with inlet passage at the oil pump mount. From there, keep brushing along the path of the oil flow. This will give you a strong understanding of exactly HOW the oil flows through your motor. You will also learn the exact locations of all of the oil passage plugs. Periodically, stop to clean off your brush. You may also use compressed air, spray carburetor cleaner, or even use a garden hose and water to flush the passages. Hopefully, you will see very little dirt/debris as you perform this task. If you do find that you are getting a noticeable amount of dirt out of the passages, keep cleaning! When you get to the cam bearing passages, if the cam bearings are already installed, you'll notice that you cannot get to them very well - do the best you can do, and don't worry too much about them unless the other passages have been exceeding dirty. If the other passages WERE dirty, then talk to your machine shop about them pulling the cam bearings and re-cleaning the block themselves.

Now scrub the rest of the block. This is tedious and time consuming, but is the ONLY way to assure you are starting with a CLEAN block! Most people use both a solvent (varsol, lacquer thinner, carburetor cleaner, etc.) and a detergent (like dishwashing or laundry detergent) with water. Use lint-free rags or a medium stiffness nylon brush (you do not want to use anything so stiff or rough that it might damage/alter machined surfaces, such as a wire brush), rubber gloves, and eye protection. Start with one (either the solvent or detergent/water) and keep scrubbing until you see nothing else is coming off, then wash again with the other. Wash with both at least twice, but keep going if you find you are still removing dirt/debris. Once finished, recheck/clean your oil galleys. Flush the block with plain water, to make sure there is no residue of either solvent or detergent. You may need to coat the machined surfaces of the block with a light oil (like WD-40®) as the block dries, to prevent surface rust from forming.

You can now install your oil galley plugs and freeze plugs. Be sure to install the infamous passenger side rear lifter galley screw-in plug, which is accessed via the press-in plug found at the back of the block.

NOTE: This plug is omitted at an alarming rate, even by "professional" shops. Without this plug, you will have insufficient oil pressure once the motor is at operating temperature, and the rearmost passenger side lifters will rattle due to a lack of oil.

Most of these plugs will be easier to install if the block is on the ground instead of mounted on a stand, so it can be rolled on end. You'll probably want to use some sort of sealant on the plugs. Permatex ®Aviation Cement® is one choice, but there are others that work as well.

The machine shop will install any or all of these plugs for a very modest fee, if you do not feel comfortable doing so yourself. Keep in mind that they will not be doing the extensive cleaning I've described above, unless you specifically request for them to do so. If you do request the cleaning, you will probably be shocked at how much it will add to the final bill!

The BEST way to install any press-fit plug is with the proper sized tool designed for this specific job. Most likely, you will not have these tools nor know anyone that has them. It is perfectly acceptable to use a socket or some other device that is of similar diameter to assist in hammering the plugs into place. DO NOT hammer directly on the plug!

Before you begin hammering, look at the plug and the hole it is going in to. Have an idea of how deep you need to install the plug. If you hammer the plug too far into the hole, do yourself a favor and buy a new plug instead of trying to use the old plug over. It will have been compressed by the first installation and may no longer fit tightly enough.

Once all the plugs are installed, and the block is still on the ground, take this opportunity to install the camshaft. Rotate the block so that it is sitting vertically, with the front pointing up. This will allow you to drop the cam straight in, minimizing the chance of the cam bearings getting gouged by the cam lobes. Make sure the cam bearings are clean, the cam is clean, and apply some assembly lube to the cam's bearing journals. The cam retaining/thrust plate may be temporarily installed, to eliminate the chance of the cam sliding out. This is the perfect time to assure the rear cam plug was installed properly (it needs to be deep enough to fit snugly in its hole, but should not contact the camshaft). Put the engine back on the engine stand.

page 2 (Bottom End Assembly)...

Copyright©2001 Lee Atkinson

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