How much oil did you put in? I have found that more than a couple of ccs will raise the apparent compression because it reduces the volume of the compressed cylinder significantly.
Compression Test Help?
- Thread starter NocalFJ60
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- #22
I got a brand new guage yesterday and did a compression test this morning. I am not very happy with the numbers. It looks like my rings are kinda worn but my head gasket is leaking too. Anybody have ideas on these numbers? I put about 1/4 oz. oil in each cylinder for the wet test with the turkey baster from Safeway.Looks like my cylinder number 6 is good. My vacuum at the intake manifold is 19 inches.
These numbers seem low since my cruiser has 130K miles. I guess when I bought it 9 years ago it had been abused.
Dry/Wet:
1-113/125
2-93/98
3-118/133
4-130/134
5-115/125
6-143/150
These numbers seem low since my cruiser has 130K miles. I guess when I bought it 9 years ago it had been abused.
Dry/Wet:
1-113/125
2-93/98
3-118/133
4-130/134
5-115/125
6-143/150
IDave said:
That is the only conclusion I can come to.
I don't think it is something that I should worry about. My thinking is that the dry compression readings indicate good rings and good valves so the increase in compression had to do with the reduced cylinder volume.
Nocal:
What kind of gauge are you using? Press in and hold type or screw in.
Those are some low readings, I read somewhere that readings under 120psi need to be looked into. But overall I think that consistency between the cylinders is most important.
I have never changed the head gasket on a 2F, I have changed it on my fuel injected 22R. It looks to me like the 2F could be easier. Alot less stuff in the way. I would start the head gasket and see what that does to your compression.
My vacuum pulls the same 19 in. my gauge is tied into the break booster hose which goes into the intake manifold closet to the number 6 cyl.
Where do you take your vacuum reading from?
Last edited:
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- #24
Civil1 said:
I am using the screw in type with a nice o-ring to seal. I am reading the vaccum from the same spot at the small line coming out of the intake manifold that hooks into the big line going to the brake booster.
I need to pass smog to get the DMV off my back so if I can pass even with these bad numbers I neeed to fix the smog problem first.
THanks for the help.
Compression isn't great, but if you're getting 19" of steady vacuum, you should be able to tune a good carb to pass smog. I think you've got a decent shot at it without putting work into the motor for now. You'll want to make sure the VTV on the thermostat are working. Otherwise, timing will lag, and the hi speed test will show high CO from retarded timing. Good luck
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- #26
65swb45 said:
I am getting 19" of steady vacuum and my carb was rebuilt a couple of years ago. I will test the VTV with my factory smog manual, set timing, check valve adjustments, and adjust the carb to factory manul.
What else should I concentrate on first?
THanks for the help.
It seems incongruous to me that you can have that low of compression and still get 19 inches of vacuum.
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- #29
IDave said:
True. I don't know. Both of the guages are brand new.
I am confused about why cyl. 6 is so much higher than all the others. Maybe my head gasket is bad on all the others except 6.
I rather think that you have worn and/or carboned up valves (and worn rings, probably) in all but #6, rather than a headgasket issue. If you had 2 or more adjacent cylinders that were equal and very low I would be thinking more about that. If you have oil in the coolant and/or coolant in the oil, start thinking about the head gasket.
Can the vacuum be different in different areas of a connected closed system like a manifold? Intuition tells me that it is physically unlikely.
Can the vacuum be different in different areas of a connected closed system like a manifold? Intuition tells me that it is physically unlikely.
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- #32
IDave said:
Why do you think it is my rings? It seems like the cylinders would have came up higher on the wet test if it was my rings? I am getting a lot of white smoke but no oil seen in top of radiator and oil looks fine.
Maybe the rings are all ok but the valves are bad on 1-5.
Thanks for the help.
Just gut instinct. If your valves are worn I'll bet your rings are, too. You do, after all, get some improvement with the addition of oil in several of the cylinders. I would start with having the head done, and replace the headgasket when you do it, of course. Then see what I had. Might be livable.
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- #34
IDave said:
Cool. I will do that after I see if I can pass smog.
Thanks again