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Discussion of rebuilding the engine block or "bottom end" as we call it. Depending on your goals, you may choose different components, but the bottom end must be rebuilt to make any real power. These mods are what you consider an investment in your car.

The first thing to do is find a reputable machine shop. If you can, ask local DSMers where they took their engines. Otherwise, get out the phone book and call the performance shops in town for their recommendations.

Cost | $400 and up
Power | 1pt in compression ratio = 4% horsepower at the crank.
You'll want to upgrade to forged pistons. They are more durable than the stock pistons, which are cast from powdered metal and are prone to breaking under severe duty such as excessive boost or nitrous. Stock compression_ratio (CR) is 9.6:1. All motor builders tend to favor higher CR such as 10.5 or maybe 11.5, but the higher CR you run, the harder it is to tune and the less likely it will be that you can turbocharge the engine safely. Turbo guys will tend to go with a lower CR like 8.8 so they can run more boost without detonation. Compression refers to how much the pistons compress the air and fuel in the cylinder. A turbo does the same thing by forcing more air into the cylinder through the valves. Piston selection requires some thought. Pistons will usually come with rings.

(Connecting) Rods
Cost | $400 and up
Power | None. (Use of long rods allows higher revs and slight increase in torque.)
If you're upgrading to forged pistons for any reason, it's a good idea to upgrade the rods at the same time. Do it right the first time. For most people a set of Eagle (brand) rods will do the trick and be all they need. Others will opt for Pauter or Crower rods just in case they intend to make more than 500hp. Long rods are special, in that they modify the rod_ratio and increase dwell_time at top dead center (TDC), which means they can handle higher engine speeds and provide a slight increase in torque. This is probably the only thing to think about when shopping for rods.

Cost | $150 and up
Power | None, directly.
You will want to ensure the cylinders are perfectly concentric and have a fresh surface for the piston rings to seal against, so you'll likely have them bored over. Common overbores are "twenty, forty, sixty," and "eighty." This refers to the increase in diameter of the cylinder as a result of boring it in thousandths of an inch. You will not see gains from such small amounts, so it's best to get the block bored only as much as you need to ensure concentricity. Twenty over is generally fine on all but the most damaged blocks. After the cylinder is bored, it is honed to slightly rough-up the surface to promote piston ring sealing. The head gasket mating surface will also need to be prepared for the new gasket.

Machine shops will also machine your crankshaft to accept larger main and rod bearings, if you by any chance "spun" one. While they are working on your engine, they will clean it, install new freeze plugs and can even balance the moving parts (pistons/rods/crankshaft) so they spin smoothly and last longer. There are charges for everything, so know your budget in advance and be sure to ask them about what, exactly, they do for a quoted price, and how much for those things which are not included (like the balancing).

It might be worth your while to ask what they charge to assemble the "short block" for you. This is your engine block with the pistons/rods/crank/bearings installed. They will make sure your bearings are all clearanced properly and even ensure proper piston ring gaps. When you get the shortie back, you just have to bolt up the head and accessories and it's ready to install in the car!

Miscellaneous 1
Cost | $500 and up
These are other components for the rebuild you don't want to forget! Get a new oil_pump, water_pump, rod bearings, main bearings, and a lower gasket kit. This gasket_kit comes with all the gaskets you'll need to put the bottom end together without any leaks! It should have the front and rear main seals, an oil pan gasket and the sometimes forgotten bedplate o-ring (this will result in a leak that requires removing the entire engine to repair if you forget it). You'll also want to pick up a multi-layer steel (MLS) head gasket (HG) for between the block and head when you put it together. If you can afford it, most of us suggest you also get a set of ARP head studs to bolt the head back into place securely. They're around $120 for a set, but they're great insurance against a HG leak right away.

Miscellaneous 2
Cost | about $50
The part about a rebuild that really kills most of us is the random stuff that comes up when you're elbows deep into the build and find you forgot something or need something you hadn't anticipated. In addition to the things listed in Misc 1, don't forget to buy at least ten quarts of the cheapest conventional oil you can find to use for the first few miles while you're "breaking-in" your new engine. Get a couple filters too. You'll need more coolant/antifreeze for the cooling_system, as well as anaerobic sealant and some high-temperature RTV for some seals.

Something else to consider, if you haven't done the timing belt yet, now is an excellent time to get all new timing components and install them while the engine is out of the car (this is SO much easier than when it's in).

Finally, with the engine out of the car, you have perfect access to the clutch/torque converter in the transmission. Do some homework on which clutch to buy if you're looking to upgrade, and consider installing it now while it's easy to do.

How long will all this take?
One lesson you will become almost intimately familiar with in this hobby is known as "The Contractor's Triangle." Basically, and we've touched on this before, you can have anything you want for car done right, done fast or done cheap. Of those three, you can only get two. An example, if something is going to be done right and be really cheap, chances are it's going to take some time. Just like, if something is cheap and fast, you might have problems when it comes to quality. There's almost no getting around this paradigm.

The best suggestion for limiting down time, especially if this is your only car, is to find another short block out there somewhere. You might be able to find one for anywhere from free to $300. You take this block, along with all your internals, to the machine shop. They do their thing, you do yours, and then you have a new shortie ready to go when you pull your old engine out. If you wanted to, you could then sell your old engine if you can bear to part with it (you'll probably start being attached to things at this point) to offset the cost of the second block.


Document statistics: Last modified on 2006-08-08 09:28:39 by DR1665

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