compression dry/wet test question.

[RHON]

I've got a little bit of burning oil, so when I did the compression check dry, on the first crank the gauge would read about 100 psi and after about three or four cranks would hit a solid 175 psi across the board.

Then when the test was repeated with oil in the cylinders , the gauge would hit about 125 on the first crank and end up around 250 psi after the fourth revolution.

Now the Hanes manual doesn't get real specific here and am having trouble understanding if the rings are worn or not- there is a big diferance with the wet test, or does the dry test sound OK ?

 

[fastjim11]

My 1976 2F FSM does not say to test wet, it says insert the gauge open the throttle fully and measure the pressure while cranking. The 2F engine s/b 149.3 to 113.8 psi.

 

[RHON]

Yes , the engine should be at operating temp with the choke and throttel fully open , The wet test is to make a seal between worn rings and the cylinder - that is supposed to confirm ring wear, the 22r should come in around 171 psi - were close to that, I'm trying to determine where the burning oil is comming from.

Yes my fj60 has low compression also all the way down to 116 in a few of the cylinders- this is due to the complete incompitance of the "persons" that rebuilt my 2F, but that's a whole nother story.

Any more thoughts on the 22r here?

 

[fastjim11]

According to my Chiltons manual 22R comperssion should be 171 psi, and not more than 12-14 variance between cylinders. Several cranking revolutions is correct , so it sounds to me like your cylinder rings and bores are ok. I'd look elsewhere for the cause mybe the valve guide. Does it smoke? If so does it doit all the time? Does it doit when you let up on the throttle? Or when the engine rpms are winding down?

 

[2ndGenToyotaFan]

Sounds like the rings/valves are all working great! I'd look to the valve seals.... they can be changed on the truck if you're really careful. You have to pull the headbolts to get to them though..... So it's a little a little touchy when everything is loose....

 

[KLF]

I don't put a lot of faith in compression test readings. A leak-down test will tell you a lot more.

 

[RHON]

Thanks for the feedback- while throtteling up there is a little smoke but is much more prevelant when throtteling down,what would this indicate ? it idles clean, the number one plug was oil fouled but the rest were all clean.

 

[2ndGenToyotaFan]

Letting of the throttle ups the vacuum a lot, I'd say valve seals. If there's a lot of miles on it, maybe to the headgasket while you're in there.....

 

[RHON]

sounds like good advice, so your guessing just valve seals and not the valve guides themselfs? - as this would be the best case scenario.

 

[tehcruiser]

I would agree with the valve seals too. Those things become brittle and start cracking after a while, and like 2ndGnToy said, you can change them without taking the head off. Just make sure the cylinder that you are working on is at TDC, so you don't loose a valve.
You could pressurize the cylinder with some compressed air to put the valve keepers back on. Good luck.

 

[2ndGenToyotaFan]

The valve guides are just a tube that the valve shaft rides in, so that it's not wobbling around, the seal goes right on top of the valve guide to keep oil from getting down into the combustion chamber.

 

[RHON]

Thanks guys, sounds like I can tackel this when time alows me to, so, at first thought I figured the engine was just worn and was assuming it was time for a long block and looks like if i can just slide by with a seal job things will really be looking up - especialy since i've already saved up for a longblock = a new set of tires and just maybe some wheels.

So is it really necessary to presurize the cylinder and if so how much psi would be recomended?

 

[tehcruiser]

Thanks guys, sounds like I can tackel this when time alows me to, so, at first thought I figured the engine was just worn and was assuming it was time for a long block and looks like if i can just slide by with a seal job things will really be looking up - especialy since i've already saved up for a longblock = a new set of tires and just maybe some wheels.

So is it really necessary to pressurize the cylinder and if so how much psi would be recomended?

You could pressurize the cylinder to whatever Psi keeps those valves closed, (10-30 PSI?), but of course you are not gonna blow the cylinder with 250psi, it's just a matter of safely managing whatever PSI you use, or use a clean thick wire through the spark plug hole to push the valve up and closed.

 

[2ndGenToyotaFan]

What you want to do is pull the valve cover, remove the head bolts, careful now.... You don't want to bump the head, or you'll need a new head gasket... Loosen all the valve adjusters, remove the rocker assembly. and find some spacers to re install some of the headbolts to hold it still while you work on it.

With the head secured, pull the plugs and get some rope. Yes rope Thread some rope into the spark plug hole and turn the engine over to hold the valves up. Remove valve springs, replace seals, replace valve springs. Repete for all 4 cylinders. Replace rocker assembly, and head bolts and valve cover and you're on your way.

Make sense? The pressurised cylinder is not that good of an idea, if it fails the valve will fall, and even if you have the piston all the way up, it'll be near impossible to get the valve spring back on if it dropped an extra 3/8 or 1/2 inch..... So use the rope trick (not that rope trick!)

 

[RHON]

Thanks again guys- sounds like goood advice, i'll give her a shot when i can get to it .

 

[RHON]

Bump.... seals are done, I just wanted to extend my thanks once again and to HIGHLY recomend the rope trick- it's the magic rope trick, and you can't go wrong ( even me ) , the old 22r stopped smoking and the truck is ready for the next phase.