Mike96z

iTrader: (78)

Alright, here are the numbers, Im thinking I have a burnt valve or bent push rod or something maybe bent valve, it pops and backfires, alot of valvetrane noise on the passenger side. Not sure what compression should be but here it is.

#1 210
#3 220
#5 200
#7 210

#2 210
#4 180
#6 180
#8 (didnt do it, too hard, tried for an hour) guessing its around 200)

Let me know what anyone thinks of this. Help is appreciated.

lt4malibu

iTrader: (39)

The minimum compression in any one cylinder should not be less than 70 percent of the highest cylinder. No cylinder should read less than 690 kPa (100 psi). For example, if the highest pressure in any one cylinder is 1035 kPa (150 psi), the lowest allowable pressure for any other cylinder would be 725 kPa (105 psi). (1035 x 70% = 725) (150 x 70% = 105).

Normal -- Compression builds up quickly and evenly to the specified compression for each cylinder.

Piston Rings Leaking -- Compression is low on the first stroke. Compression then builds up with the following strokes but does not reach normal. Compression improves considerably when you add oil.

Valves Leaking -- Compression is low on the first stroke. Compression usually does not build up on the following strokes. Compression does not improve much when you add oil.

If two adjacent cylinders have lower than normal compression and injecting oil into the cylinders does not increase the compression, the cause may be a head gasket leaking between the cylinders

and "guessing" at number 8 is not going to help you, try going from under the car.

Mike96z

iTrader: (78)

Either way im pulling the heads, went from under the car, theres no way im getting it in there without pulling the headers. Is 180 too low if the max one is 220. I didnt get a chance to see how they built up on the strokes because I was the one turning it over. I used the tester for 1 day and cant get it back unless I buy one. Im gonna check for a bent pushrod next, then a fuel pressure test on it and if that doesnt help me with anything, heads are coming off, my 856's or whatever are going to be replaced with some freshened up 241's or 243's with some new pushrods and springs, also lifters, i think replacing it all wont hurt, just wanna know what the numbers mean.

Mike96z

iTrader: (78)

If I calculated it correct then my lowest could be 154 psi.

beedo

iTrader: (28)

Depending on what gauge you used the diff. is pretty good. Anything over 100 psi will HIT, and it looks like your good and the diff. is within reason.

Mike96z

iTrader: (78)

Thanks, not sure what it could be. Its missing really bad at idle and at running. Lots of valvetrane noise.

99blancoSS

iTrader: (115)

Ok first of all dont guess on #8, you have no idea.

I had all of them at 180 and one at 60... and the car ran fine

Second they are ok, 180 is more common than 220 from what I've seen of people posting them.

180 to 220 is a bit of a variance, but again 180 seems to be the norm. Maybe you got that variance from technique?

You did pull the fuel pump fuse right?

Mike96z

iTrader: (78)

pulled the fuel fuse for injectors in all, there is no way that compression tester is going into number 8, when I pull the headers and im about to pull the heads, ill slip it in there, im pretty sure its gonna give a normal reading. Maybe theres more room in an LSx car but in a swapped car, well atleast mine, there is no room, I have the hooker super comp LT's and makes it nearly impossible to get that hose on there with the headers installed. Im going to pull the heads no matter what, wanna go to a better casting. Thanks for letting me know that 180+ is norm, thats one thing I needed to know. The plug in #8 looked good too. Technique was, pull the plug, insert the hose, had someone watching the guage and seeing how it came up on the guage, then I turned it over until it met max pressure.

stevied916

iTrader: (30)

I fit my compression tester in #8. If you dont do it there was no point in doing the other ones

studderin

iTrader: (28)

pull all the plugs
unplug the coils
push the gas WOT, crank it, do 4 compression revs (WOT cranking= no IPW, no need to do anything with the fuel pump)

do it on a cold motor, or a warm motor fast. RnR the plugs on a car with airtubes and AC your going to take to long if its still warm.

Mike96z

iTrader: (78)

thanks for the info. so only turn the car over about 4 times? that's about how many times I did it but a couple were more.

studderin

iTrader: (28)

without the plugs you can hear the singal compresion stroke easly. 4 is just a good number. if you have weird numbers or doing a leak down, adding oil ect. you can do more, just dont over heat the starter.


un-pluging the coils:, I forgot to say just the 1 large white conectors to the hanress along the fuel rails, works great.

pureluck1

I had to register just to call you a fookin idiot.

jamiesls1

iTrader: (4)

Now delete your account and leave thanks. People like you are worthless. This forum is about learning and helping nothing to do with insulting. Want to do that hit youtube.

JRENIGAR

iTrader: (37)

So what does that make you? A fookin dumbarse?

prokilllsx

sometimes you can just tell who voted for Obama.

badazz81z28

iTrader: (6)

Classic....Did you realize the post is from 2009?? The guy hasn't even browsed or posted the site since 2009