Interpreting compression test results (1 Viewer)

[WCBlueSky]

Did a compression test today (out of curiosity sake). Engine was warm, throttle wide open, cranked for 5 turns. FSM says 171 psi or more, with 128 psi minimum and no more than 14 psi difference, so I'm within these specs, but seems to be on the low end? Wet vs dry appears to be worn rings? I do live at 5000 ft above sea level, so that makes some difference. I also did a block test and there were no combustion gases in the coolant.

DRY:
#1: 137 psi
#2: 138 psi
#3: 140 psi
#4: 140 psi
#5: 133 psi
#6: 140 psi

WET:
#1: 173 psi
#2: 190 psi
#3: 178 psi
#4: 210 psi
#5: 165 psi
#6: 180 psi

 

[TurboDennis]

Those are good results, i wouldnt worry about it.
Yes, the numbers are a bit low, but that could be attributed to the particular tester you were using. Or a weak battery/starter. Or elevation like you said. Or any other number of things.
As long as the numbers are close to each other (which they are in your case), you're G2G.

I've seen 1FZ's that tested bellow min FSM spec and ran absolutely wonderful, burning no oil and not having any other symptoms of low compression.

 

[OffGridOverland]

#5 is low, And the rings are worn.
Otherwise I'd just keep an eye on #5

 

[ppc]

Did a compression test today (out of curiosity sake). Engine was warm, throttle wide open, cranked for 5 turns. FSM says 171 psi or more, with 128 psi minimum and no more than 14 psi difference, so I'm within these specs, but seems to be on the low end? Wet vs dry appears to be worn rings? I do live at 5000 ft above sea level, so that makes some difference. I also did a block test and there were no combustion gases in the coolant.

DRY:
#1: 137 psi
#2: 138 psi
#3: 140 psi
#4: 140 psi
#5: 133 psi
#6: 140 psi

WET:
#1: 173 psi
#2: 190 psi
#3: 178 psi
#4: 210 psi
#5: 165 psi
#6: 180 psi

What quantity of oil did you add to each cylinder? The dry results seem consistent from cylinder to cylinder but the wet results are completely inconsistent.

 

[WCBlueSky]

What quantity of oil did you add to each cylinder?

I wasn't very careful and used a funnel to pour in some amount of oil without measuring, so that is probably why the results aren't consistent...

 

[ppc]

The volume of the 1FZ combustion chambers is 69cc or approximately 4.66 tablespoons so if you even added 1 tablespoon of oil the compression is going to rise by over 20%.

Post #3 stated the rings are worn in cylinder #5 yet there is no evidence to support that statement. Almost all of these motors opened up find the rings and cylinder walls are still in good condition. If you have a high consumption of oil then it might make sense to have the head machined, valve grind and valve seals replaced. Otherwise I think based upon elevation where you tested there is no inherent problems that are being displayed.

 

[WCBlueSky]

Here are the spark plugs. Replacing them as part of an engine tune up. #1 is at the bottom.

 

[ppc]

Those plugs look to be in excellent condition with the electrodes almost looking new. Little sign of burning of oil but there is a small amount of oil on the threads which indicates leakage past the spark plug tube seals.

 

[b16]

As long as the numbers are close to each other (which they are in your case), you're G2G.

This