I need help with my 2f compression Test. (1 Viewer)

[Slow85]

Ok so I started out just doing some maintenance on my 85 fj60 because I snapped my throttle cable on the Webber 38. So I fixed that with factory cable and Edelbrock universal termination kit, and tuned the carb.

Then moved on the swapping out my factory distributor and NGK plugs and wires that are about 6 years old to the fire cracker distributor from TPI and Toyota plugs and wires I have had sitting around for a year or so.

Now keep in mind the truck runs perfect I’m on 37s with 4.11 and have no problems it doesn’t smoke, oil stays constant between every oil change (12k) adding a 1/2 quart total maybe, It does leak oil front timing cover, rear oil pan, and small amounts in the inspection cover. Stays right at the first 1/4 tick on temp even when off-road doesn’t Move much here in Florida at 95-100 outside stays consistent.

So for some reason I wanted to check the compression!

So The truck had been sitting in the drive when I got home from work, I cranked it up. Let it idle for 10 min. Then pulled all the plugs they look old, big gaps, dirty, hot, but not wet and didn’t smell like oil or fuel. Just used So all and all ok. I disconnected all the distributor wires except the two vacuum lines.

Proceeded to do a dry test and I didn’t know there was a difference between wet and dry At this time.

I hooked up the gauge hand tight and bumped the ignition for a second on each cylinder. The gauge read 90 everytime. Well that’s bad I’m looking at my FSM and it says between (high 149) and (low 114). On Cylinder number 2 I had left the ignition on for about 5 seconds and the gauge read 135 so I’m not doing it right stoped read thru a ton of posts Q/A. And I have a firm grasp on how to now! But still have a few questions can you guys take a look and tell me what you think. Thank in advance. Austin.
Questions

1. How long do I keep the ignition on? I know from reading several posts. Anywhere for 6 to 10 rotations but how long is that. Because the longer I I keep the ignition on the pressure goes up from instant 90 to 134. In about 4 to 5 once that cylinder strokes? Would it keep going up or does the high number reflect my actual compression?

2. How much oil give or take mostly take do I need to inject into the cylinder for a wet test.

3. What is the best method to do a wet test. Do I need to put the correct amount of oil in all 6 cylinders. Then come back and start the test 1-6. Or start with (#1 inject oil, test) (#2 inject oil, test) (#3 injection oil test)? And so on?

 

[OSS]

My advice is don't test the compression. Everything was "fine" until that inaccurate gauge was hooked up. Questionable readings from a compression test have sent more people with a good running 2F chasing after ghosts than is civilized. I'm a firm believer (now) of never checking the compression on a 2F unless there's an obvious power or rough idle issue. It's only gunna bum you out or cause concern

 

[Slow85]

Ok because it’s good now I don’t have a idle problem or temp problem or oil. I just thought I would check It. Before I installed the new distributor and plugs and now has stressed me out.

 

[GLTHFJ60]

Throttle has to be all the way open when you do a compression test, or else you'll get a false low reading.

 

[Slow85]

I had the carb wide open.

 

[GLTHFJ60]

Good.

When I had my 2F, I'd crank until the compression gauge peaked. If the first crank is 90, then the next is 110, then the next is 135, then the compression is 135 per my understanding.

For a wet test, put maybe half an ounce of oil into the cylinder via the spark plug hole before you put the compression tester on. Crank until the compression gauge peaks, just as above. Will likely take more cranking for the pressure to peak than with the dry test.

FWIW, my 2F "ran real well" with compression between 90 and 110psi. It can run well with low-ish compression, you just won't make as much power.

There are lots of older threads that talk about this topic.

 

[2mbb]

From what I remember, I usually got through 5 or so compression strokes. As Johnny say's, you are looking for the maximum pressure achieved--however long that takes, but it should take about the same amount of rotations for each cylinder.

Besides the accuracy of the gauge, there are a lot of other factors that may influence your measurement--strength of the battery, resistance to air flow (carb throttle position), resistance to turning (all the spark plugs removed or just one), even the oil viscosity. On a good engine, the faster it is turning the higher the reading will be...in general.

with all these factors, each individual pressure reading is not as important as how they compare to one another. One or some cylinders that are lower may indicate there is something wrong with those cylinders. If they are all about the same, then assume everything is OK, unless you have some other symptoms (oil consumption, low power, etc.).

 

[Slow85]

Ok I just got home going to run they the motions again I will keep you posted.

 

[Slow85]

Ok cleaned and re gaped the old plugs put them it and drove around for 20 minutes. Ran that a scalded dog. Parked it pulled the plugs and did a dry test.
1. 135
2. 149
3. 149
4. 134
5. 150
6. 152

Now 7 rotations of the motor seemed to give me the highest number or 8 seconds.

 

[NeverGiveUpYota]

I always turned the key, stepped on the gas and did a count of 10 for each.

 

[klinetime574]

Those numbers look good. I agree with @OSS I tested mine once and said “what the heck.” Haven’t cared about it since and my 60 runs fine.

 

[Willard]

My advice is don't test the compression. Everything was "fine" until that inaccurate gauge was hooked up. Questionable readings from a compression test have sent more people with a good running 2F chasing after ghosts than is civilized. I'm a firm believer (now) of never checking the compression on a 2F unless there's an obvious power or rough idle issue. It's only gunna bum you out or cause concern

Well said.

 

[87CRUSR]

Those numbers look good. I agree with @OSS I tested mine once and said “what the heck.” Haven’t cared about it since and my 60 runs fine.

Same....many moons ago.

 

[OSS]

did a dry test.

Just for a reference point, when my 2F engine was 2 years old (in 1988) with 36,000 miles on it (pretty much still a new car) I did check my compression. If I recall correctly, my highest number was 152psi in one cylinder and the lowest was 135 psi in another - and that pretty much was a new engine

 

[Slow85]

Ok those numbers are very close to mine but my motor is far from new. It has 309,000 on it But I’m going to take the advice and stop worrying about the compression. Because it runs amazing the valves are loud at times. I never have checked them but that is also a can of worms.

 

[87CRUSR]

Ok those numbers are very close to mine but my motor is far from new. It has 309,000 on it But I’m going to take the advice and stop worrying about the compression. Because it runs amazing the valves are loud at times. I never have checked them but that is also a can of worms.

I am no technical expert but low compression and valve adjustment are two different issues.

 

[GLTHFJ60]

I am no technical expert but low compression and valve adjustment are two different issues.

Not necessarily. Improper valve adjustment can cause low compression numbers, among other run issues. If a valve is stuck open due to an eroded seat, or being adjusted way too tight, you will have no compression.

They can be different issues, but they're not completely unrelated.

 

[Dr. John]

""I never have checked them but that is also a can of worms. "" Don't understand why you wouldn't want to keep your valves adjusted?? Easy peasy. Too loose...lost power, excess wear on valve train. Too tight... risk a burnt valve. Then you'll really open the worm can.

 

[FJACS]

If you follow the FSM, I bet you can adjust the valves in less time than it takes to do a compression test.

 

[87CRUSR]

Not necessarily. Improper valve adjustment can cause low compression numbers, among other run issues. If a valve is stuck open due to an eroded seat, or being adjusted way too tight, you will have no compression.

They can be different issues, but they're not completely unrelated.

Thanks for the clarification!!