compression test after rebuild

[97redgsx]

ok well i finished my build about a month ago, i used topline "oem" rings and i just wanted to put out my numbers:

150, 151, 150, 152 (i also only cranked for about 2 sec. on each cyl, so they might have been higher if id kept on it longer)

its been about 4000 miles, and i thought they seemed to be pretty good.

the main reason that i am posting this is because when i was doing my build i did ALOT of research on the subject of honing vs not honing, i did NOT hone my cylinders, my car had 130k at the rebuild and still had ALL the factory cross hatch. so i hope that somebody in a similar situation that i was in can make a decision on whether to hone or not.

 

[luvmygst]

Was the car at operating temp when you did the comp test? I re-ringed my motor and did not hone and im close to 180 across the board.

 

[IceMinion]

150 is bad, especially for a rebuild.

Although since you did not hone your engine it makes sense.

You said you did ALOT of research and I am extremely interested, can you cite your sources?

As it turns out, you really should have honed your engine

http://www.mototuneusa.com/break_in_secrets.htm

read it all

 

[97redgsx]

it was not at op temp, but it was not cold....

 

[fwdeclipse]

Thats silly to do a half ass compression test. Go drive the car till its at full operating temp. Make sure you hold the throttle wide open and crank it for more than 2 seconds. You need to have somebody watch the guage and when it stops going up stop.

 

[97redgsx]

so i read more about it and i did a few things wrong,

1 i was not at op temp
2 i didn't hold WOT
3 i did not crank it long enough

so ill post back soon with the updated numbers.....

 

[Littlebeeper]

That is pretty low for a 2G. mine was 150 but it was a cold test with a low battery. I replaced the battery for the last 2 cylinders and got 160 on those 2. not bad for showing 155K miles on the clock. oh, and i'm a 1G also

2G standard compressression is 178
service limit is 133

1G is 164 and 121 service limit

your at the middle with your readings. try it a full temp and hold the throttle open. seems like a waste of hard work to get you to 1/2 service compression

 

[luvmygst]

150 is bad, especially for a rebuild.

Although since you did not hone your engine it makes sense.

You said you did ALOT of research and I am extremely interested, can you cite your sources?

As it turns out, you really should have honed your engine

http://www.mototuneusa.com/break_in_secrets.htm

read it all

i didn't hone my motor and my compression is fine.

 

[IceMinion]

i didn't hone my motor and my compression is fine.

What you made makes no sense, the post above you just finished telling you that your compression is NOT FINE.

yes, it is EVEN, but NOT FINE

if you read the whole article in the link (it is a good read) you will understand that the honing creates a rough surface that "custom grinds" all of the rings to perfection.

you may still see honing marks from the factory, but overall it has been smoothed out, there is no grinding of the rings going on anymore.

please please read the article, and you will understand.

 

[No_Skillz]

How is close to 180 across the board not fine? Ring seating doesn't soley depend on honing. Maybe he could have gotten away with it with a proper break in. Let's wait on the correctly done compression test before we jump to any conclusions.

 

[97redgsx]

ok i re-did the compression test properly, i got 180 on all four cylinders....thats with a Snap-on compression gauge too so its accurate

 

[Locke]

What you made makes no sense, the post above you just finished telling you that your compression is NOT FINE.

yes, it is EVEN, but NOT FINE

180 is good compression.

Ring seating doesn't soley depend on honing.

Cylinder pressures, vacuum, and the rings own tension, flexing it against the cylinder's hone, is about all that seats a ring.

 

[repoman9622]

Sorry to open an old thread, but as I was reading though it I was wandering.......
Why does the motor need to be at full operating temp......and how different would the cold numbers be?
I have my turbo off(a lot of oil n exhaust, car smokin) assumed needed rebuilt. Turns out after pulling the turbo off I see oil in the manifold. I pulled the manifold and found oil by the valves. My valve stem seals/valves are only and year old(actually the whole head is that fresh). After pulling the valve cover, everything I can see looks fine. My next option would be rings right(even though they only have 15,000 on them). So again how accurate would the test be without putting the motor back together, to start and get to op. temp and any suggestions to the original oil problem would be appreciated.
Oh BTW....got a catch can and no oil at the upper IC pipe/TB.

 

[Burnett03]

Was the car at operating temp when you did the comp test? I re-ringed my motor and did not hone and im close to 180 across the board.

Why would you re-ring a motor and not hone it?

 

[jamisonj24]

Repoman. Your best bet is to do a leakdown test, instead of putting it back together. If you put it back together and do a compression test and it turns out bad then you still should do a leakdown test to isolate the problem. As far as operating temp goes, when the engine gets hot your rings expand to seal up like they should, when they are cold they usually don't seal and you get low compression numbers.

 

[repoman9622]

Thanks jamisonj24......I didnt have a decent air compressor available where I took the turbo off(assumed turbo.....diagnosed the problem without checking anything else ), but I'm gonna go ahead and tow the thing to my shop where I do have a good compressor. Also checked the head gasket over the weekend and looked fine.