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Rebuilding your B18/B20, part one
Phil Singher>

This series should help the novice successfully rebuild a B18 or B20 motor. Options will be described for those wishing to do the least expensive job, the "back to new condition" rebuild, and for those who want modify their motors for increased power.

The B18/B20 is extremely straightforward -- motors just don't get any simpler than this. We'll try to warn you of any pitfalls you might encounter, so you can approach the rebuild with confidence. While the specific case described here is that of a B18 from a 122S, most of the information will also apply to other models of Volvo if you are willing to interpolate just a bit.

In this issue, we cover:

  • How to tell if you need a rebuild
  • Should you keep it stock?
  • Preparing for the project
  • Removing the motor from the car
  • Evaluating the work to be done

In the next issue, we'll complete the project:

  • Tearing down the motor
  • Ordering parts
  • Machining and balancing
  • Building the new motor
  • Installing the new motor
  • Initial starting and break-in

Whether or not you find the process to be fun, we're sure you'll come out of it with a car that runs well and increased confidence in your abilities. Good luck!

Do you really need a rebuild?
The main indication that a motor is worn out is low compression or excessive oil consumption (chunks of piston flying out of the carburetors is also a definite sign). The original-style rear main seal can leak badly and may fool you into thinking that you are burning oil, so I believe a compression test is the best way of evaluating your motor's condition. You can buy a compression gauge and perform the test yourself for about the same price you'd pay to have a mechanic do it. This is best done with the motor warm and the valves properly adjusted. Here's how:

  • Pull the large center lead out of the coil.
  • Remove all four spark plugs.
  • Screw the compression gauge (or hold it firmly, depending on the style) into the spark plug hole on #1 cylinder (the forward one).
  • Have a friend crank the starter motor for a few seconds while you observe the gauge. It will pump up over five or six piston strokes and then stop. Record the reading.
  • Repeat for the other three cylinders.
A healthy motor will pump up to at least 145 pounds on the gauge (high compression B18B and B20E motors should pump more than 170 pounds), and all four cylinders should read within a few pounds of each other. If you get uniformly low readings, or one cylinder that reads well below the others, the head will need to come off. While you can remove the head with the motor in the car, I strongly recommend that you pull the motor so you can give the block innards a good inspection. This will keep you from having to do work twice.

Just for the record, there is a test which can indicate that the problem is limited to the head: squirt a little motor oil into the spark plug holes and repeat the compression test. This will temporarily cause the rings to make a good seal. If the compression does not improve, the problem is in the head. If it comes up to spec, the problem is the rings. If it improves but not enough, the engine is generally worn. Our personal experience has been that limiting the work to a valve job usually results in having to rework the rest of the motor within a year anyway, so it pays just to do the whole motor at once.

Do you really want a hot rod?
These motors were derived from a Volvo V-8 truck motor, and they retain its huge main and connecting rod bearings. There is a lot of "extra" metal in the block, as well. The motors therefore lend themselves to drastic overboring, and the bottom end will stand for just about as much power as you care to produce without compromising reliability.

The downside of modifying is mainly the extra expense involved, even compared to replacing everything with new stock parts. Those big overbores will cost you four times the machining cost of a plain .030" over job, and leave you with nowhere to go with the next rebuild. A steep cam will require having the head machined to fit double-wound valve springs. You will have to install different needles in the carbs or increase the pressure to your injectors -- this can lead to a lot of "trial and error" before satisfactory tuning can be attained. Your fuel economy may also suffer somewhat, and the raised compression that goes with overboring will have you running premium grades of gasoline. Smog checks can also become more challenging.

Consider your driving needs and budget carefully. If you do decide that you want that extra power, there's lots to be had, and it adds little difficulty to the rebuild other than the extra machining.

You will need a place to work on the motor -- in the driveway won't do. You will need a sturdy workbench and enough room to manuever. The motor takes up a lot more room when it's apart than you might expect. Clean up part of your garage and put the clutter away somewhere. While it is nice to have an engine stand to hold the motor while you work on it, you can get by with two cinder blocks under the motor mount "ears" and a stack of boards at the rear.

For the majority of us that don't have a professional-style parts cleaner available, I recommend taking a trip to your local car paraphenalia store (Pep Boys, or whatever is in your area) and your hardware store to buy the following items:

  • a one-gallon can of parts cleaner with a dipping basket
  • a plastic oil-change pan for soaking larger parts
  • a gallon of mineral spirits (never clean parts in gasoline)
  • a couple of stiff paint brushes
  • a few sets of rubber gloves
  • a can of Liquid Wrench or other "frozen bolt loosener"
It is also useful to have a few old toothbrushes on hand for scrubbing small crevices.

You will need a system for organizing all the hardware that will come off the car and the motor. Zip-lock freezer bags (the kind with a label area) are a good way of keeping related parts together and identified. I also use a couple of old kitchen drawer organizers (those things that keep the knives apart from the forks) on my workbench where they won't get tipped over. I am not a fan of keeping hardware in old tin cans -- it's hard to see what's in them, and the parts tend to scatter over half the county when Bosco the neighbor's Rottweiler gets so happy about your project that he has to jump up on your workbench to congratulate you personally.

Don't start ordering parts for your motor before you take it apart and determine what you'll need, but make contact with suppliers. In my opinion, if you are in North America, your best source of rebuild kits and high-performance parts is ipd. Individual stock parts are best bought from RPR. Click on over to their websites and order catalogs from both.

Assuming your tool kit already contains a good set of sockets, extensions, combination wrenches and an assortment of screwdrivers, take a trip to your discount tool store and buy the following:

  • an eighteen inch breaker bar to fit your sockets
  • a presentable torque wrench (the beam kind is OK)
  • an 11/16" crowsfoot wrench
  • an 11/16" socket
  • large long-nose pliers
  • a piston ring compressor
  • a set of hex wrenches
Depending on what you find inside your motor, you will most likely need more tools before you're done, but you will certainly need all of these as a minimum. In the next issue, we'll cover all that as well as how to get by without those special Volvo-only tools referred to in your manual (no, those tools that ipd once rented are no longer available).

Here is a most important step: pick out a reputable automotive machine shop. It doesn't have to specialize in Volvos or foreign cars. Ask friends for referrals, and ask to be shown the prospective shop's work area. While such shops are often cluttered with engine blocks and can't be expected to pass a white glove inspection, you don't want to see tools scattered around the floor in a week's worth of metal shavings. Good shops are generally busy, so it's a good sign if lots of work is being done -- it also means you will have to wait a bit for your job to be finished, but that's a price you pay for competence. Realize also that the garage down the street gives these people a lot of work and they will be given priority over your job. Be nice to the machine shop and be patient with them -- the quality of your rebuild depends very largely on their expertise.

Finally, you will need an engine hoist and a head chain. Unless you plan on doing rebuilds regularly, it is cheaper to rent these from a local outfit than it is to buy them. Hoists either break down into pieces that will fit in a van, or they can be towed using a standard trailer hitch. Locate a place that will rent you these items by the day or half-day, and have a plan for getting the hoist to your work location.

Here is a basic rule of car repair: "It will take longer and cost more than you think." Don't let this discourage you -- it will cost less than having someone else do it, and you'll be sure of the quality of the job. Do be prepared to have some slack in your budget and alternative transportation for a month or so.

Pulling the motor is easier if you have a helper. So, if you've gotten all of the above in place and you're ready...

Section two: Removing the motor

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