Performed compression test: pass or fail???

[dkrugg24]

I performed a compression test on my fully rebuilt 2g gsx and at first of the build it tested 170 across the board and now 300 miles later I notice smoke from the exhaust so I performed the compression test and this is what I got.

From left to right
Cyl.1- 137
Cyl.2- 146
Cyl.3- 140
Cyl.4- 140

Are these results normal after only 300 miles? I also noticed that Cylinder 1 had smoke coming out of it after I pulled the plug but none of the others did. Could this mean bad rings? Or just the rings haven't fully seated on the break in yet and I'm getting blow by?? This is also not a stock rebuild it is a fully built head and block. PLEASE HELP!!

 

[boost97gst]

Well, thats low but atleast theyre all in same ballpark... Smoke wafting out of one cylinder doesnt mean alot. It couldve stopped on the exhaust stroke and not all of it exited the chamber.

after my break in with stock CR 2g mahle's i had almost exactly 180 across the board. maybe 185, i cant remember but it was maybe off 1 psi on any given cylinder, aka, margin of error

 

[vingasoline]

I had 165 when I built my engine, 4000kms later still 165.

Maybe you need a leak down test to see what's going on.

What break in method did you use?

 

[dkrugg24]

Well I haven't really got a chance to break it in yet I've only gone around town a little bit and one highway trip for about 180 miles which I know wasn't probably the smartest idea but I did change speed and rpms through out the trip but that's probably what got me.

 

[Dsmkauai]

You need to go thru a few heat cycles, then retorque the head bolts. The actual procedure has you loosen and retorque. And break in should be 6/800 miles. You want to get the break in done and out of he way, and done properly of you miss the window your screwed. This could be your smoking issue and why the numbers seem low, the head has lifted slightly.

 

[spyderdrifter]

Did you do the wet portion of the compression test? That'll tell you if your rings are the issue or the head gasket. Those numbers, although good for being close to each other, are nearing the service limit for a 7 bolt (if you have a 7 bolt still). Your 'break-in' time, is basically the first 20 miles it's driven, so you've surpassed that. How did you break it in? That info would help use diagnose this for you more. Like Dsmkauai said, if you missed the break-in window, you're screwed on power and your engine will not perform to its potential.

 

[dkrugg24]

I have not yet retorqued the head studs but that is next on the agenda. It was broke in with non synthetic oil and easy driving. What is the "wet" portion of the compression test? Is that when you put about a teaspoon or so of oil into the spark plug hole and test?

 

[spyderdrifter]

Yes, the wet portion is putting a little oil in each cylinder while doing the compression test (1 at a time of course). If compression goes up, your rings are bad, if it stays relatively the same, your head gasket is bad.

 

[dkrugg24]

And yes it is 7-bolt

The wet portion is putting a little oil in each cylinder while doing the compression test (1 at a time of course). If compression goes up, your rings are bad, if it stays relatively the same, your head gasket is bad.

Thanks spyder that's what I thought but wasn't sure

 

[spyderdrifter]

No worries Just glad to help.

 

[dkrugg24]

And with retorquing of the ARP head studs should I loosen them first then tighten them down or torque, lose, torque again? I was told torque spec is 85-90ft lbs, anyone know if this is true or not? Thanks for all the help I really appreciate it!

 

[spyderdrifter]

I can't comment on that. I've never used them, yet. Will be on my next engine though, so would be nice to know.

 

[Dsmkauai]

re torque using the steps to 90ft/lb. I think I even did mine to 110 last time .

 

[donniekak]

If anything compression numbers should go up after a few hundred miles. Was your tune lean, or getting detonation?

 

[901gtsi]

And with retorquing of the ARP head studs should I loosen them first then tighten them down or torque, lose, torque again? I was told torque spec is 85-90ft lbs, anyone know if this is true or not? Thanks for all the help I really appreciate it!

7-bolt arp head studs (11mm) are to be torqued to 80ft lbs in 3 steps 25/50/80 ft lbs. 6 bolt arp head studs (12mm) are to be tourqued to 90ft lbs in 3 steps 30/60/90. hope I could help.

 

[dkrugg24]

If anything compression numbers should go up after a few hundred miles. Was your tune lean, or getting detonation?

Well it's running rich I can tell that by the Wideband, and also when I pulled the plugs they were black on the ends and cylinder 4 plug wasn't as black and had a white spot on the electrode.

7-bolt arp head studs (11mm) are to be torqued to 80ft lbs in 3 steps 25/50/80 ft lbs. 6 bolt arp head studs (12mm) are to be tourqued to 90ft lbs in 3 steps 30/60/90. hope I could help.

Yes this helps a lot! Ill use this method and torque them this weekend and retest the compression and hopefully the numbers go up! Thanks again this all very good helpful info.!

 

[boost97gst]

There is a difference when torquing with moly lube and oil.... pretty significant from what i was told by a machinist. Moly might by 80lbs but oil might be 100lbs. Just rough figures, nothing scientific but thats what a very experienced machinist told me about my engine after he built it.

And break-in? Should be done after 50 miles . Moto-man bro! You need to run that thing hard and seat the rings and get through a few cycles. A highway cruise on a new engine is the worst thing you can do aside from idleing it for an hour straight

 

[4G63gst1990]

Not trying to intrude but what is the recommended way to break in a 4g63t 6 bolt thats fully built

 

[dkrugg24]

do I loosen all the bolts at once then torque or on at a time?

 

[BogusSVO]

Personally I would not loosen the head bolts, you run the risk of getting fluids on the HG.

If you want to check head bolt/stud torque, set the torque wrench to about 50 ft/lbs then step to your final torque. if your final is 80 ft/lbs you may go to about 85 ft/lbs

 

[901gtsi]

There is a difference when torquing with moly lube and oil.... pretty significant from what i was told by a machinist. Moly might by 80lbs but oil might be 100lbs. Just rough figures, nothing scientific but thats what a very experienced machinist told me about my engine after he built it.

And break-in? Should be done after 50 miles . Moto-man bro! You need to run that thing hard and seat the rings and get through a few cycles. A highway cruise on a new engine is the worst thing you can do aside from idleing it for an hour straight

Yes you are right there's a diffrence in torque when using moly or oil I forgot to mention that.Thanks for catching that. Im just so used to using moly when torqueing my studs .

 

[BogusSVO]

300 miles on the build, a couple oil changes by now I am sure.

The moly you used is still packed in the threads, and under the nut. The excess has been washed away, but what is backed in the threads is still there

Also did you use the same tester for both tests?.

 

[dsmcurse]

Personally I would not loosen the head bolts, you run the risk of getting fluids on the HG.

If you want to check head bolt/stud torque, set the torque wrench to about 50 ft/lbs then step to your final torque. if your final is 80 ft/lbs you may go to about 85 ft/lbs

Best advice in this thread

Why would you loosen any of them? never heard of that at all

I can see after a few hot-cold hot-cold cycles pulling the valve cover and doin a lil mini re-tourqe on the ARP's.

When I put my engine togeher, like a month later I pulled the valve cover and put a trust worthy tourqe wrench back on 'em to see.

Its my opinion to tourqe the head in a 3-stage process. personally i went like this, oil soaked ARPs (not molly-lube) tourqed in sequence to 33, then 66, then the finall at 99

Seems to be working good for me so far, I got 3 years and 20,000 hard miles on my build and she puts out over 600WHP every single day...

I didnt use molly lube because of excess and spill over. The freakin thing is a home-made just for fun kinda engine/car. Its not like its a all out competative race machine!

Use oil, its more trust worthy in my opinion. Personally, at the end of the day, I think it just boils down to preferance

 

[Dsmkauai]

^^ Just because you haven't heard of a method doesn't mean it doesn't exist! Ok about the loosening, I am searching for we're i read about this and I swear Brian from Terhune raceworks (17+ master Mitsu tech) was the one that told me about this. Anyway reading over a break in sheet he supplied me he only mentions a retorque after 3 heat cycles. If anything I would have said only slightly loosen one at a time in order then retorque. This is how I installed my arp's last, I did one at a time then after a few heat cycles I loosened and retorqued and everything worked out perfect. The reason im talking about loosening the head stud is. You dont want air trapped under the stud, this will affect torque. If you back the stud out you will hear when the Air pushes out then you tighten back down and your good to go. And the torque will hold mich better and be accurate. Anyway for now just ignore what I said about loosening and ill edit that out for now till I find the proof behind why, but I believe its valid.

 

[dkrugg24]

300 miles on the build, a couple oil changes by now I am sure.

The moly you used is still packed in the threads, and under the nut. The excess has been washed away, but what is backed in the threads is still there

Also did you use the same tester for both tests?.

I've only done one test so far. This weekend I'm goin to pull the valve cover and retorque the ARP head studs (used with moly) and retest with the same tester. If the numbers are still low I'm going to do the "wet" test with the same tester and go from there.


Thanks everyone once again! I appreciate all the input and advice you have been giving!