Normal 2F Compression

[vtcruiser60]

I think I located a good replacement candidate for my dead 2F. I was quoted the following compression figures. Do they seem right? They seem high to me.

1985 FJ60 117K
185 180 175 175 180 185
6 5 4 3 2 1

 

[Doc]

No, not high, they seem reasonable for a used motor, how may miles?

 

[vtcruiser60]

The motor has 117K on it.

 

[HZJ60 Guy]

All mine were at or above 600 PSI!

Oops, that's because it is a DIESEL!



Sorry.

TB :whoops:

 

[swank60]

I thought the 2F's factory compressions was only 150psi?

 

[Doc]

hmmmm I guess I don't know the factory specs for compression. I was comparing to my Honda- but they generally have pretty high compression- so it might not be a good comparison afterall.

Ignore the noob.

 

[60wag]

Has the head been shaved? Any mods to the motor or stock? I'd be a bit suspicious of the numbers being that high. Its possible the pressure gauge wasn't accurate or maybe they had a really high cranking speed to do the test. Would a double battery setup crank it faster than a single?

 

[vtcruiser60]

I don't believe that the head was shaved or recently rebuilt. The motor is coming out of a grandpa's land cruiser....low miles, low wear and tear.

My understanding is that variance about the cylinders is more of a problem than high or low compression. I understand you want them to be within 10 percent of eachother. But, I thought that normal compression was between 160-180. With some readings at 185, I got a little concerned. Maybe this is just normal carbon deposits.....

 

[swank60]

Was the test done with the engine warm? Did you do a wet and dry test?

 

[jwest]

For reference, here are the OEM specs at 250 rpm:
149 standard
115 low limit
< 14 psi difference between cylinders.

If the figures are correct, I'd say the motor pings.

 

[hj60]

Low miles on an old rig? I'd suspect carbon buildup on the pistons.
Check the plugs.

 

[vtcruiser60]

Jwest....what do you mean the "motor pings"?

Hj60.....I was somewhat leery about a low mileage motor....but at 117k, it looks like an average of 4-7k per year. What would cause a carbon build up? I know some carbon is normal. The reason I ask is to see if carbon is indicative of any other problems.

 

[jwest]

[quote author=vtcruiser60 link=board=29;threadid=17273;start=msg167738#msg167738 date=1086185716]
Jwest....what do you mean the "motor pings"?

Hj60.....I was somewhat leery about a low mileage motor....but at 117k, it looks like an average of 4-7k per year. What would cause a carbon build up? I know some carbon is normal. The reason I ask is to see if carbon is indicative of any other problems.

[/quote]

Detonation, meaning that the motor will "ping" or detonate, usually at higher speeds. This is caused by premature combustion in the cylinder chamber due to over-advanced timing, low egr, bad fuel, excess heat, increased compression from carbon build-up or a rebuild, etc.

The carbon is a normal by product of combustion. Problem with low mileage or overly babied engines is that they usually aren't driven long, hot, or hard enough to partially self clean, causing a buildup.

If carbon build-up is creating high compression, there are off the shelf products you can try. I've used "Sea Foam".
There's no harm in using this, but we haven't even established if your motor detonates.

 

[vtcruiser60]

Thanks for the replies. I believe the compression test was dry and cold.

Would premature detonation or pinging cause any motor damage?

I know generally that premature detonation is problematic....in my marriage especially, but in the 2F I am less clear.

 

[jwest]

[quote author=vtcruiser60 link=board=29;threadid=17273;start=msg168485#msg168485 date=1086282603]
Thanks for the replies. I believe the compression test was dry and cold.

Would premature detonation or pinging cause any motor damage?

I know generally that premature detonation is problematic....in my marriage especially, but in the 2F I am less clear.


[/quote]

Lol... In both cases, it doesn't hurt every now and then but it's something that's gotta be taken care of if it's chronic. (BTW, there are some things you can do for that. )

For the motor, long term knocking will damage your pistons and rings.
...something you'd want to "stay up" on.