So you have read the GM Build Book and thought to yourself "I want to do some of this on my car". This always leads to a lot questions from people about the stuff in that book. Here's is my recommendation for the people that actually want to do this. This is a high power street build. Not a race engine.

First, the build books 400 HP build is designed around the idea of NOT removing the engine from the car. It has you replace the pistons using the original rings in order to avoid having to hone the block. My recommendation removes the engine, and uses new rings.

First, and most importantly, use a core engine. Don't pull your stock engine out of your car, thereby leaving you without a usable car for a month. A core engine can be had for around $500. And considering what you are going to spend on the other parts, that's not much. And the fact that it allows you to take as much time as you want on the build pays for its self.

Next, leave the core engine alone until you have all of you parts ready to go. Here is why. Assume you take your core apart and then get the block work done, but you don't have your rods or pistons yet. Now your freshly honed block is corroding while you wait. You want to put the engine together as soon as possible after it has been cleaned and prepped.

Here is the list of stuff you need to collect before you even begin turning a single screw...

The Core Engine. There are many different cores you can get. First, an identical L61 works perfectly. You can also get an older L61 with EGR cast head with some modifications to the head. You can also get an LSJ core, but you will have some decisions to make about the head later.

Rods and pistons. The build book give a good description of available parts. However, there is one very confusing part in there concerning the use of stock LSJ rods. The LSJ rod has a different size piston pin, and won't work with any L61 piston. So, GMPP made a very specific piston for use in the L61 using the LSJ rod. That is the piston discussed in the build book.

Use Studs instead of bolts. You have to replace the main bolts and head bolts anyway as they are one time use parts. Studs can be used over and over again, and provide better clamping force then bolts.

Cometic or Stock head gasket. The stock head gasket is actually very good. However, like above, if you are going to spend the money, get the Cometic.

Bearings. Stock bearing are excellent. Aftermarket is fine too.

This completes the short block assembly. Now you have to make some decisions concerning your head.

There are a lot of options here, and they all have to do with your budget. You will spend some money for anything above a stock head. I don't want to focus on the scope of each, but instead just list them breifly.

1. The stock head, no modifications. It's good to 7000 RPM and between 3-4 hundred horsepower with stock cams.

2. A stock head with aftermarket valve train. That gets you over 8000 RPM and very high horsepower with high lift cams.

3. Any non-stock head. This includes an older L61 with EGR, an LSJ, or any of the GMPP heads. Using these requires a bit more planning.

Porting and polishing is an option for any of the above, but it totally up to the individual. Say you want #2 with a P&P? Patriot performance can hook you up with a complete package.

There are two other items you need to consider. They are the GMPP adjustable cam gears and the neutral balance shafts. I highly suggest the use of the gears. Did you know the LSJ cam and the L61 cams are identical except for the timing? With the gears, you can set any timing you want. Additionally, it allows easier manipulation of the torque band. You can do more adjusting the timing of a stock cam then you can do with an aftermarket replacement cam with fixed gears.

I don't recommend the balance shafts. The stock units are good to 7000 RPM. Unless you plan on spinning faster then that, stick with the stock units. The power draw of the shafts is minor compared to the power you can make, and it keeps the engine street friendly and smooth.

Now you have a complete long block. There are other small things, but they can be addressed after the assembly of the block.

Now you are ready. Take the core apart. Use a stand. Throw away the following as you do: (all the stuff you bought)

1. Rods, pistons, and rings.
2. Bearings
3. Main and Head bolts
4. Head gasket
5. Cam gear bolts

Take the subassemblies to your local machine shop for the following. You can remove all of the freeze plugs for a better cleaning result.

1. Hot tank, bead blast, and wash all the parts (oil pan, girdle, block, head, oil pump)
2. Hone the block
3. Polish the crankshaft
4. Have the rotating assebly balanced. The shop should assemble the pistons to your rods for this.

At this point, you may decide to allow the shop to do your assembly for you, or you can take the components home and do it yourself.

Now you have a completed block. Ready to install in your car whenever you are. And when you're done, you'll have an extra engine that you can sell to recover some cost, or to rebuild again!

Approximate pricing:
Core engine $500
Bearings $50
Rods $400
Pistons $500
Studs $300
Head gasket $120
GMPP cam gears $350
Head From Zero to $2000
Machine shop work From $500-$1000
Miscellaneous stuff $500

So, you're looking at between $3200 - $5700 for an engine that can safely handle from 350HP @7000 RPM to over 500 HP at over 8000 RPM.

 

i will be the first to say nice write up! alot of information covered in a fairly short explaination.

 

Great write-up!

 

Halfcent you are the man. I have never seen better wrtieups before. Between you and NJHK I feel like i can read my way through any problem. But I think I will probably be doing this this winter for the turbo setup. But if i have any more questions I will def. look in your direction for help.

 

awsome info, thanks man....

 

sweet write up, too bad I dont have between $3200-$5700... lol.

later

 

Figured I'd throw this in, never get any aluminum parts hot tanked ever. The typical hot tank uses caustic soda to remove dirt and junk, caustic soda will dissolve aluminum. A good machine shop should have a parts washer in addition to the hot tank. A parts washer is basically an upright over powered washing machine. It uses very hot soapy water so its safe for all parts.

 

Great write up! Thanks, this will come in handy soon.

 

Nice post!!

 

Thanks for the write-up. Gives me a guide line so I can explain it to the wife. She likes seeing things wrote out instead of me just saying.

At least it'll keep me busy at nights in the garage. LOL!!!! Now the funds is a concern.

Man I'm new to this wife husband thing...how do you guys do it? Patience or good budgetting? I'm on a strict budget, but I do want to still tinker around on the Cobalt.

 

its a natural oposite with wives and cars (expensive hobby) i am fighting with my fiance about it now. i just said "i had enough of this shitty cobalt, its not safe for kids and im tired of the problems/ future issues. im going to trade it in!" then after she starts stewing about another car payment, i slipped it to her that ill just keep the car, but ill have to make some improvements. thats what i did and so far it worked.

 

I just paid a couple tool bills off, and all. My main thing is I have a sorry ass hourly job at the dealership. Nice thing is she likes doing this stuff, but we both have our unborn child in mind as the baby savings account is 10x bigger than my car fund haha. Guess I'll enjoy the big toys here in a couple years after all the BIG stuff is settled as far as a place to live, etc.

Back on topic...if I want more opinions theres a off-topic for that.

 

If the cobalt is not your main transportation and you want to save money, the way GM does it in the car is fine, just be ready for problems (and you may have problems even if you do it the way halfcent has).

 

Only thing I can see that is a wate of money are the adjustable cam gears. Even gm states im most cases they find that leaving the cams to exact spec in relation to oem cam gears is ideal up to 7k. What ya need is a set of cams honestly.