Engine Commpression Testing

BlackHawkRacing · #1 (**permalink**) 08-11-2005, 10:47 AM

Im looking to get my engine commpression tested and was wondering were it could be done. Im located in CT and i am willing to travel to mass. if nessacry to get it done.

Thanks,
Scott

Chapel · #2 (**permalink**) 08-11-2005, 01:39 PM

Suggestion: Bring it to the cheapest, most reputable mechanic you can find and have them do a compression check.
There's nothing special that needs to be done to do one...
Any $45/hr mechanic could do it. Just make sure he's an honest one. It's a pretty simple test to do. Only takes about an hour (of billed labour). Probably won't even take them 30 minutes to do the whole job though. Might want to have your spark plugs replaced while you are at it.
May I inquire to why you need one done?

BlackHawkRacing · #3 (**permalink**) 08-11-2005, 02:22 PM

o i thought that you something special needed to be done, didnt know any mechanic could do it. Thanks.
Plan on doing a turbo soon so im going over my entire engin and i just wanna see how the engine is holding up and weather its worth it to rebuild the entire engine or not.

Chapel · #4 (**permalink**) 08-11-2005, 04:16 PM

nope, the compression check tool just screws into the spark plug holes

Then you crank the engine over either by hand or with the starter motor (not a great idea unless you make the proper preparations by pulling fuses for spark and fuel) and voila... compression numbers
However, if you are planning on forced induction, I would go the extra step and have a leakdown test done as well.
It's similar to a compression test, but it involves shooting compressed air into the cylinder. It lets you see how good your combustion chambers are sealed. Pump 100psi of air into the engine at TDC and if the gauge returns 95psi, then you have 5% leakdown. Acceptable leakdown percentages on a tight engine are no greater than 10% (new engines exhibit between 3 and 5%). Also, note the variations as well...
If 5 cylinders show 3% and 1 shows 10%... you may have an problem. At the very least you'll have a weak point that boost might exploit on that one piston. The variation shouldn't be too much between cylinders.

I think good compression numbers for an S52 are 160 across the board, but don't take my word for it. I'm not 100% on that. My car is around 155, 156, 155, 154, 154, 152 from cylinder 1 through 6, respectively (but I also have an M20 engine)

BlackHawkRacing · #5 (**permalink**) 08-11-2005, 04:45 PM

Thanks for the info on the commpression as well as the leakdown, i will most likely have that done too.

Thanks again