Engine Rebuild Headaches

[FJ40 that green thing]

So Check this out: 1975 FJ40 found it with WAY low miles in good shape other than it needed an engine. So, about 2 years ago I buy a cheap but complete 2F that I knew would probably need some rebuilding. Had the engine installed and reputable machinist completely rebuilt, resurfaced, etc. etc. the head and got her running.($1800) It ran very well but was burning tons of oil so thinking, "rings shot" took it into a different mechanic about a year later, told him I wanted this thing completely gone through rebuild the block everything but the head probably wouldn't need it cause it was just done. So, they pulled the block had it completely rebuilt ($3000) Put her back together got it to pass emissions everything seemed great. Well, 2500 miles into the new rebuild I am still losing a quart of oil every 2-3 tanks of gas. So the block rebuild has a warranty and I take it back into them they say the chromoly rings might need some time seating drive it a little more. Took it back into them and they ran a compression test. Numbers are like 120/86/122/90/108/124 what the heck? Mechanic suggests possibly cracked head or bad head gasket. It is in the shop right now and I am sure he will be fair with me on the expenses and everything but what the heck is going wrong here? It has never overheated since I have had it could the head have cracked since the block being rebuilt? Should I look into a new/rebuilt head? Looking for some advice before I sink any more money into this. Thanks guys

 

[IDave]

Woah. Poor compression. Rings or valves. Wet test each cylinder (5cc engine oil). If the compression improves, its your rings. If the compression does not, its your valves, basically. Bad head gasket? Maybe. Should be oil in your water or water in your oil for sure (believe me, I know! ).

You can also vacuum test it. There is a great guide under technical links on how to interpret. Tells you LOTS of stuff.

Certainly a mechanic should know these things and you should know a lot about what you are getting into before he starts unbolting stuff. Invest $40 in a compression tester and a vacuum gauge and check it yourself. You'll learn a lot and, even if you don't do the work yourself, you'll have an idea what you are asking for.

 

[Cruiserdrew]

Just a long shot, but have you adjusted the valves since the rebuild? If they are adjusted too tight, your compression could be off. That's at least simple and cheap. After that do a leak down test and see where the compression is going. As to the burning oil, do you know for sure the valve seals in the head are good? Your long block should be ok, so I agree with the approach of fully investigating the head before you look elsewhere. Good luck, that sort of thing is aggravating.

 

[FJ40 that green thing]

man you are not kidding... I'm guessing the block is out of the question as well. I do know that the valve seals are good for sure because I had my mechanic check those again just to make sure. He is going to probably take the head off mon to check things out. Hopefully we can figure out whats up. Thanks for the input

 

[Romer]

You might PM Treeroot, I think he has some 1F engine parts he did not post in his yard sale.

 

[TonkaC]

Are you running synthetic oil in it? If you are, you want to change to normal oil for the first couple oil changes. Synthetic oil will prevent the engine from seating everything correctly. That will cause excessive oil burning and compression errors. Just a thought.

Chris

 

[Landpimp]

do the leak down test when the motor is warm, cracked head might only show up then, but I wouldn't think that would cause oil to burn?

vavle seals would cuase it to smoke at start up.

are you seeing it burn oil?

 

[FJ40 that green thing]

This is a 1978 2F engine sorry, forgot to mention that in the first post. I had thought about running synthetic in it but had not done it yet. I wanted to be sure everything was running good before I did that. My mechanic has done all the work on this rig and I'm pretty sure he did a leak down test with it warm. He thinks the head could be cracked because there is a loss and big difference in compression numbers now with the compression test. I'm kind of hoping the head gasket just failed but I don't understand why that would happen. Adjusting the valves is a good suggestion, I'll have to ask him about that. Before the rebuild I could see blue smoke coming from the tail pipe it was pretty obvious it was burning the oil but now I just get a puff of black smoke upon start up and then it goes away. I think it also needs a carb rebuild eventually thats probably why I get that. Another thing, I've checked the whole PCV valve thing thinking possible blow by was happening but it all checks out just fine. This whole thing is a little frustrating though. I'm thinking of gettin it fixed up and just buying a newer FZJ80 instead. Anyone want to talk me out of that? Thanks again