if i had decide id say i got a problem.
but i had a hard time getting the cheap tester tube screwed in to the spark plug thread so it made me think there is a chance this was not too accurate, but most likely have some issue causing the loss of compression

test done on cold engine

first test notes: went through the cylinders fast, throttle body was closed.

second test notes: only did left side, got 180 instead of 150 in cylinder 5, made me think i wasnt screwin the thing in tight enough and started taking alot of time to ensure the tube was screwed in properly.

third test notes: screwing it in didnt make a difference, third time only did a few, did it with the throttle body open wide and used a adapter to ensure tube was properly screw on, didnt really make a difference either ( with throttle body or adapter)

this is not the real cylinder order but this is the one im using (number 1 and 5 are the front of the engine)
motor is a 91 tpi 350 5.7l chevy motor from a firebird and i think the proper compression should be 180 psi

motor no signs of leak at all. no coolant loss, no drips on the floor. i dont drive this truck. motor oil always looks nice and clean, smells like gas though.

first test
150 [8][4] 170
150 [7][3] 150
145 [6][2] 150
150 [5][1] 180


second test
150 [8][4]
140 [7][3]
152 [6][2]
180 [5][1] 180

third test
[8][4]
[7][3]
150 [6][2]
~167 [5][1] ~167

 

I'd do it again to check, but the big variation suggests you at least need a new set of rings and possibly a lot more.

How is the oil consumption and engine blowby when you pull the PCV?

 

havent checked that dont know how. how do you check it?
is the pcv valve the one on the right valve cover or the left valve cover

...but like i said i dont drive the truck much so i couldnt really tell if its burning oil or how much oil loss happens. i bought it 3 months ago and have drove like 5 or 7 times just to let it run

 

What color is the spark plug tips?

The insulator should be a light brown. If black you might have a work engine that is burning oil.

 

All test results are GARBAGE. It's not a "test", it's just "practice". (kinda like what lawyers do, except they do it at your expense) Period, paragraph, end of story.

Throw out all that stuff you posted and start over, and do it RIGHT this time.

Block the throttle wide open. Remove all the spark plugs. Disconnect the plug at the base of the dist before starting the test, so that fuel and spark aren't fed to the remaining parts. FULLY charge the battery before EVERY cyl, FULLY, not "I charged it a little bit", so that the engine always spins as fast as possible.

Then use the REAL order. Do it RIGHT. Use the correct numbering so everybody that looks at it can make sense of it. Otherwise, it's GARBAGE.

Cyls are: odd on the driver's side, even on the pass. 1 & 2 are in front.

 

That pretty much sums it up.
I just went through this and technique is everything.
A warm engine is best.
And be sure the engine is cranking over at a decent rate. As was posted, a fully charged battery is a must.
Which reminds me, I'll have to do my again.

 

oh the spark plug tips looked great. they are light brown, all of them smell fine too.

 

honestly with a warmed of engine and fully charged batt i think im going to get the same results. in fact the battery was prob fully charged today and as for the doing it with the throttle body wide open, it didnt even make a difference (if you didnt read my post) most of the compression readings were the same as the first test i just left a few out on the third.

although i was already going to do it again .....im not convinced doing it again will make a difference. also since theres a loss of 30 psi how much can i really gain by warming up the motor. also are you asking me to charge the battery after each cyl??


why would it matter what order i do them in? can yo give some reasoning behind this. i mean is that hard for you to under stand what im talking about when i do this:

[8][4]
[7][3]
[6][2]
[5][1]
front of the engine

the cyl numbering was just to show what cyl im talking about. why is it "garbage" since its not in the right order your mind suddenly just cant comprehend what im talking about...??

 

ill do it again with a warm engine i just forgot. hopefully it helps id prefer to get consistent 180 psi's lol, although i already planned to rebuild the motor before the test.

i was cranking 5-7 times each time till i saw the gauge stopped reading air.

 

Make a note of what you get on the 1st hit, what you get after 5 and then as you've done, till the gauge doesn't advance any more.
Remember that slower cranking speeds will yield lower results. If your battery is fully charged and it doesn't appear to be losing too much during the tests, that's about all you can do. And a warm engine and throttle held open will generally give higher results too. (Your results may vary). Keeping the cylinders in order allows for easier diagnosing (for those of us that are watching).
180 PSI across the board would be good wouldn't it?
Good luck.

 

you mean on the first "crank"? i remember exactly what it psi cranked up to on the first, i remember it being pretty strong and going pass 100 psi on the first

 

Doesn't too much matter what order you do them in; only, the names you give to the cyls.

Using the correct numbering is like using the right words when you post. You wouldn't post the word "green" if you were talking about what everybody else calls "red", would you? No difference between that, and using the right number. Your results won't be any different (just like the thing will be whatever color it actually is no matter what name you give it) but it'll be AHELLUVALOT eeeeezier to discuss it coherently if you use the right numbers.

Warm engine helps make the test more realistic, since it more nearly duplicates operating conditions, but as long as the temp is stable for all, you'll get the consistency you need. In fact it could be argued that a large difference between hot and cold readings is a diagnostic, as well as all the other analyses you could do on whatever results you get.

You will get VASTLY different results with the throttle open vs closed. Not only the absolute numbers, but also, consistency. With it closed, variations in cranking speed are magnified further: as cranking speed increases, the engine will actually start to develop considerable manifold vacuum, and air that's rarefied to begin with (i.e. under partial vacuum) will compress to a lesser ultimate value regardless of how many times you turn it over.

Yes we are telling you to charge the battery after each cyl. You're going to be moving the fitting over and whatnot; that takes time; might as well just hook the charger up and let it do its thing while all that is going on.

Technique is EVERYTHING in getting accurate, reliable, meaningful results. You won't get useful actionable information if you're sloppy. Instead of your numbers telling you what condition the engine is in, they'll only tell you how much variation there was in your technique.

 

Yes. Exactly that. It's just another part of the test that can yield significant results. 100 PSI is a good thing.

 

what do you mean by "good thing"?

i mean the results were showing over 15% difference in the 150 psi cylinders so i should be assuming somethings wrong internally. Although this other guy doesn't think i did the compression test perfectly when i do it again i feel that im going to get the same results. if they dont im still looking at these first tests as valuable info.

 

still looking at these first tests as valuable info.

whether or not its going to make a difference to do it perfect, which of course im not against doing things the right way, its still going to give me some valuable info about the motor or doing compression tests. i def wouldnt immediately consider everything as "garbage".

 

Only thing those test results you posted are good for, is showing you how bad they can be messed up by doing the test wrong, when you compare them to a valid test. So I guess as a path to education they have at least that little bit of value.

 

right it is good information it is good "why not to do something" not just that "you shouldnt something"... idk why youre trying to insult these test results so much... lol, but ill be laughing my *** off if i get the same results.

but honestly i hope youre right and i get good 180s for all cylinders. but if its the same results ..well i was going to rebuild this motor anyways, so everything works out good in the end. hopefully