Doug, I'm sure there are some really good threads about compression and leakdown testing here if you do a search on the forum. But, to quickly explain it, your checking to see how well your cylinders are sealing. Both tests are done replacing a spark plug with a threaded hose and a leakdown gauge or compression tester gauge, to check the rate of leakage(leakdown) or while under air pressure or while you crank the engine without actually starting it, how much cylinder pressure is produced(compression) .Then you compare pressures from each cylinder to see if one or more are weak. There are specs in numbers for testing each model engine in like a chilton's or rebuilding books. It's a fairly easy way to identify a problem cylinder or just to get some piece of mind knowing that internally everything is producing the power that it had when it left the factory. A "tired" motor for instance would be pretty much equal in all cylinders perhaps, but doesn't make the compression(power) it once did. Almost any auto parts stores have them. If you can change a spark plug, and have a spec manual, you can do it(compression test)....A leakdown test requires a compressor. You fill the cylinder with air (80 or 90 lbs I think) that you are testing, while that cylinder is at Top Dead Center (both valves closed). I hope that helps a little, its a very crude explanation tho. Good Luck.

 

Just read all the horror stories here on a weekly basis and u will read new enthusiasts getting in way over thier head - yes every week here. Find the source of that knock Doug and if its from the engine save yourself a bundle $$$ and buy a new crate motor. Most dealers will install into a C3 for less than $1K in labor and u will have a warranty too. Then u will have a spare engine to learn rebuilding with at your leisure.
Now blue smoke on startup is only the valveseals - easy to fix and a good place to get some experience with the engine. And all those diagnosis tricks like compression and leakdown will help u understand your engines health. But if got a knock for inside the the engine - that engine life is short.

Just my 2 pennys here,
cardo0

 

- sounds like he's been there, just don't know if he's the vette or the honda.

Warranty is a good thing, especially the GM version that's honored at every GM dealer.
If you can get the power level you want / need and get insurance at the price you want to pay - why not?

 

Never owned a honda.. or a V8 that got beat by one.. Spend
a little time at the racetrack or at least arm yourself with information
by using a Quarter Mile calculator and you'll save yourself
on street embarrasment.

$1500 Civic 2500lbs 150hp stock engine with a $500 Nitrous kit/75 shot
vs. a 165hp L48 at 3300 lbs... run the numbers.. post the results.

Calculator here:

http://users.erols.com/srweiss/calcehp.htm

 

If your engine has a knock, then the last thing I would be worried about is what heads or cam to use.
Check that knock first, If a rod or main bearing is going, get a crate motor and save yourself a lot of hassles. OR, you can probably find yourself a good used motor for well under a grand with low miles, then soup that up, instead. ( After checking it over, of course.)

 

No mention of a knock till post #19 If the knock is from the engine don't even bother with the compression and leakdown test. Crate engine is your best option. If you don't know what a compression test is it is not time for you to start building motors.