Compression on my 2.8
 

Just did a compression test:

1-152
2-150
3-150
4-150

Isn't that like super good? :p

how many miles on your 2.8L? street or track?

thanks

john

What's the compression ratio of the motor?

2800mi, street car, stock ratio, but the compression should be higher because the block is decked. or at least that is what i was told

what's tq like, off boost?

Chris,

I think those numbers a perfect! Your head could be decked, our pistons are slightly lower compression than stock.

Did a check on mine at 1200 miles, 139,139,140,140 will check again when my turbo gets back from Majestic. Numbers should be higher now with 3700 miles on engine.

"Just did a compression test:

1-152
2-150
3-150
4-150"

Those numbers are just about perfect. Right inline with the numbers I get on the 2.8's. I was getting slightly higher on my 951 for about the first 2500 miles, then the motor started settling down and they ran about 155 accross all four. David's numbers are a bit lower than I spec out. He does have 3700 on the clock so his motor is past the break in point, and thats probably where his compression will sit. They look even.

Take Care!

ok well then why am i squirting out coolent from my overflow pipe every time i get on boost?

hmmm,

How much are you loosing? A couple of things come to mind. Bad seal on the head gasket? YOu can have a head gasket issue withought the extreme symptoms of a bad blow out. If you do have a slight leak, then you would really only pressurize the coolant system under boost. If it gets worse, then you will start to see the classic symptoms.

Have you done a leakdown test? Try this, put a pressure cap on the coolant tank, one that reads has clear easy to read numbers starting at 1 psi and up. Now perform a leakdown test, see if you can see a pressure change in the cooant tank as you go from cylinder to cylinder. When you do the leakdown, leave the pressure in each cylinder for at least 5 minutes...this will give even the tiniest gasket leak a chance to blead off pressure in the coolant system.

Or run the chemicle test, I use a unit from snapon, it goes from blue to yellow if it smell combustion in the coolant. Sounds like you might have a real tiny leak, so when you do the chemicle test, you should boost the car then run the test ASAP, as soon as you remove the cap, place the sniffer in the tank, try not let any air out when you remove the cap..or keep the air mixing to min.

Take Care

800mi, street car, stock ratio, but the compression should be higher because the block is decked. or at least that is what i was told

Having your block surfaced is only going to take off a couple thousands, which is not going to change your compression very much, if at all.

If you are pressurising the coolant tank, then you probably have the start of a blown headgasket as John mentioned.

Eurospeed951,

Out of curiosity;

1) Are you running a stock cam?
2) Was the compression check done while the motor was up to running temperature or cold?
3) Approx. how many rotations did the motor turn, per cylinder, for this test?

1a) Compression test results will vary with different camshafts.
2a) Cold will typically result in lower numbers.
3a) Not really critical, 7-8 revs. works fine.

Even on newer motors with 1000~ miles on the, some rings can become unseated. It is usually easily corrected by driving miles under various rpm's. I've seen some with several thousand miles, that, after they sit for a few months need to be reseated. Prolonged idling is one of the curses.

My motor when cold has 140-142~. The real beauty in your numbers is the consistency. Those numbers are as good as it gets. Excellent.