Chicagoland MG Club: Tech Tips

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  Chicagoland MG Club:Tech Tips

Engine Rebuild or Replacement Preperation

If you hold onto your old car long enough you will probably be faced with making a decision on rebuilding the engine. Should you buy an exchange unit, have yours rebuilt, or do it yourself? In order to make the decision to buy an exchange unit versus rebuilding your own, you need to consider all the costs involved, including shipping.

They key to making an informed decision is to undertake your own assessment of the condition of your engine, or have it done for you. This can be done fairly reasonably at a local machine shop, as long as the engine has been disassembled. Keep in mind the machine shop will have a self-interest in doing the machine work deemed necessary.

To compare the cost of rebuilding your engine with that of an exchange unit, start by making a list of all the major parts you will need. When making a comparison be sure to compare apples to apples. In your figures did you add the price for a new crankshaft? Do you really need a new crankshaft at considerable cost, or can yours be reground with possibly some metal added? Chances are that the exchange unit will go the cheaper route using the reground crank. Likewise with connecting rods, camshaft, etc. In all likelihood if an item can be remanufactured, the builder will choose to put in the remanufactured part instead of a new one.

With exchange units one item to be aware of is the phrase "closely inspected parts" in the fine print. What this means is that visually the part looks good, so it's reused. I'm not implying that there is anything wrong with this practice but remember, you get what you pay for.

Be sure when comparing your price to do the job against theirs, that you are comparing apples to apples. In other words what new parts are you considering putting into the engine compared to the remanufactured or 'closely inspected' parts they will use? If you decide to go the route of rebuilding your own engine, the following tips may be of use to you. Although some specific steps mentioned are unique to the MGA engine, the basic process is applicable to any job. I feel that anyone with an average mechanical aptitude would be capable of tackling an engine rebuild and I also think you'll be amazed at how simple the job really is!

The first thing I recommend is to either visit the library or get the book for your car. You will find that different books will list the same basic steps but each will offer tips to make the job go easier. For example loosen the dog nut (the nut at the end of the crankshaft) before removing the engine. If you try to loosen it after the engine is out you will have to jam the flywheel with a screwdriver to stop the crank from turning.

Before a single bolt is removed be sure you have on hand:

  1. A small box of Ziploc lunch bags.
  2. A pencil, not a pen, since your hands will be greasy.
  3. Some small pieces of paper in addition to a large sheet.

These items will be necessary to label and bag the parts once they have been removed, as well as to make notes on what is needed. Everything goes in a bag, engine mount bolts, manifold studs...everything. You'll be surprised how similar some of the parts look, especially the nuts and bolts. In fact, many of the nuts and bolts are the same, some parts however, are held on with a variety of lengths as well as a combination of sizes. The front and rear plates are a good example. An easy way to keep these bolts in order is to put a number with pencil right next to the bolt, directly on the plate. Then after making a series of holes in a stiff piece of cardboard put a corresponding number below each hole. Each bolt that gets removed gets put into the hole in the cardboard. This will leave no question as to where the bolt goes when assembly time comes.

As you are disassembling the engine, keep track of what may be missing or incorrect and the best way to do this is to refer to your Moss Motors catalog. Given the age of these engines you'll probably find bolts and washers missing, possibly substitutions made, for instance, the use of lock washers instead of lock tabs. Examine the nuts and bolts carefully. There is nothing more frustrating than to find upon assembly that a wrong nut (probably metric) was forced on a bolt, rendering the bolt useless.

After everything is bagged you should make an inventory of all the different sizes (there are actually only a few) and at the very least you should replace all the lock washers. Since most of the nuts, bolts and washers are standard hardware items you shouldn't have any problem with them. Just be sure you don't buy metric and that you get grade 8. The cylinder head nuts and studs are specialty items so plan ahead with these. Likewise the bolts, (not the nuts) which hold the flywheel are special, so check them carefully. When you order your parts be sure to include a clutch alignment tool as even if you're not replacing the clutch it will still be necessary to remove and reinstall the original. Given the effort required to pull the engine, unless your clutch is like new-replace it!

Before removing the pistons be sure to make a note of which way is 'front'. None of the books I have clearly explain how to determine the front. Phrases such as "the thrust side of the engine" are often used. If the pistons aren't marked, simply note on paper, which side of the connecting rod the bolts are, using the camshaft as a reference. If you do make a mistake you'll find that you can't rotate the crank, so simply reverse the rods. Leave the camshaft bearings alone unless they absolutely need replacing. Unless you have purchased precision bearings you'll be looking at a $200 job to have the bearings installed and then line bored.

When assembling the engine, photocopy the parts manual you'll need. This will save getting grease and oil on your good copy. It's also a good idea to write the steps down in a 1, 2, 3 order. By going over the books the night before and writing this list, you'll be less likely to forget an important step such as putting the sealant on the rear main bearing shell or putting in the cork seal before putting the rear plate on!

Another thing that helps is to write down the torque requirements and hang them on the wall for easy reference. And while speaking of torque-more is NOT better! It's easy to break a bolt or strip a nut by tightening it too much. If you happen to strip the bolts that hold the flywheel be prepared to dismantle the whole crankshaft assembly and wait for another parts shipment. An option, though by no means ideal, is to use a 3/8 24 NF tap and re-thread the bolts.

Once the engine has been installed be sure that it is correctly grounded. If you find that the starter turns slowly, or that small wires such as the throttle cable are getting hot, that's a sure sign to check the ground. It may be as simple as moving the ground wire to another bolt on the engine mount, assuming that's the grounding point.

The question that goes through everyone's mind is how long will it take? For the MGA engine figure about five hours to pull the engine, another five hours to disassemble it and about twelve hours to put it back together again. This, of course, will stretch out to about three weeks in real time, given the fact that machine shop work may be needed and parts ordered from your friendly supplier, possibly two or three times!

So the best of luck and remember, you don't have to be a brain surgeon to work on one of these engines, but you do have to be careful.

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