My 92 has developed a little bit of a knock, at idle and hot. The oil pressure is low, about 3psi hot at idle, above 1000 rpms the oil pressure is good, and the knock goes away. I did a compression test and had 125-130psi on all cylinders. I also have alot of smoke on startup and am going to rebuild the head. I do have to replace the oil pan gasket, so I will have access to the rod and main bearing. I am debating just throwing new rod and maybe main bearing in it while its open. Obviously if the rod or crank journals are trashed then there is no point in this. My thought is I drive the thing a few hundred miles per month, I really just want to stop the cloud of smoke on startup and stop the oil leaks that are ruining my garage floor. I am hoping that when I open up the pan the pickup is cloged up and that is my oil pressure problem, but thats doubtful. I am thinking that replacing the rod, and maybe main bearings would up the oil pressure if they are worn. Oh, btw, 175k, and not sure the previous owner new they were supposed to change the oil....Any thoughts on just doing bearings? The head is a given, the valve seals I believe are shot.
92 3FE rebuid question
- Thread starter bwallen149
- Start date
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My two cents:
Send out some used oil for analysis to see if there are signs of bearing or other trouble, let that guide whether or not you plan to do the bearings.
Do the head, there is lots of info here and there on slightly off-stock rebuilds (I'm doing a highly modded one, but for basics, there is replacement of the valves with stainless SBC valves that work with a boring of the stock guides and grind of the stock seats, shaving head to bump compression).
When you do your oil pan gasket, give the oil pump some attention (replace, or flip the pump gears or whatever), and have a peak at the bearings if you are still concerned.
Send out some used oil for analysis to see if there are signs of bearing or other trouble, let that guide whether or not you plan to do the bearings.
Do the head, there is lots of info here and there on slightly off-stock rebuilds (I'm doing a highly modded one, but for basics, there is replacement of the valves with stainless SBC valves that work with a boring of the stock guides and grind of the stock seats, shaving head to bump compression).
When you do your oil pan gasket, give the oil pump some attention (replace, or flip the pump gears or whatever), and have a peak at the bearings if you are still concerned.
Docs right on, the bottom end of these engines is usually very strong. An oil sample will reveal if you have bearing problems, before you mess around with them. Get the valves done, seats etc., and I'll bet you be very happy. BTW, I redid the head on my 62 by myself years ago; just go slow, carefully clean out the head bolt holes, etc, and it should work fine. Even reused the bolts. I used an engine lift to pick the head- that sucker is heavy! Good luck, 
Ned.
Ned.3FE Head
Doc and any others
I am rebuilding my 3fe I lost a rod It ran fine before that. I am wondering what I should look for on the head It looks fine I was not using oil before. Just wondering about your valve advise.
Doc and any others
I am rebuilding my 3fe I lost a rod It ran fine before that. I am wondering what I should look for on the head It looks fine I was not using oil before. Just wondering about your valve advise.
Docs right on, the bottom end of these engines is usually very strong. An oil sample will reveal if you have bearing problems, before you mess around with them. Get the valves done, seats etc., and I'll bet you be very happy. BTW, I redid the head on my 62 by myself years ago; just go slow, carefully clean out the head bolt holes, etc, and it should work fine. Even reused the bolts. I used an engine lift to pick the head- that sucker is heavy! Good luck,
If you have it off, I think it would make sense to have it checked out, shaved for a little bump in compression and power, and have the valve seals replaced (new ones should come with the gasket kit anyway). I *believe* I've seen people quote prices as low as $150 for having this done. Seats ground and valve replacement as per machinist advice (my exhaust valves are pooched, intake could have gone back in). Take this with a bit of salt, I'm doing my first rebuild, so I'm by no means an expert on it. If you see anything posted by FJ40Jim or MarkW, I would take that as gospel truth.
It would be good to know why the rod failed, and if it would have any bearing on the top end of the engine (starved for oil?), but I don't think the head needs much to hold out anyway.
- Thread starter
- #6
Thanks for the responses. I will get the oil analysis done before doing anything in the bottom end. May go ahead and replace the the pump gears while I am in there for the oil pan gasket. I was looking at the FSM, looks like there is an oil pressure relief valve in the oil pump and in the filter housing. Could these relief valves stick open and cause low pressure at idle. The knock goes away completely above 1500-2000 rpms. Actually, it idles at exactly 600rpms on the tach, I did an oil pressure measurement with my wife holding it at 800 rpms and I have about 12 psi. When I do the head I am going to clean the intake up as well, it looks disgusting in there. And replace all the vacuum lines. Hopefully this will smooth the thing out and get the idle back to 650, which I bet would get my oil pressure above the minimum 4. something psi.
If the oil pressure climbs with a slight bump in engine speed, I say that rules out a sticking relief valve. You never mentioned what viscosity of oil you have in it. If you are running something #w30, it might be worth putting in something thicker (15w40, or thicker if you are somewhere warm) when you change the oil and rechecking the pressure.
- Thread starter
- #8
I have been running 10-40 valvoline max life the last couple of oil changes, this is the oil I made the pressure measurements on. I think I may go ahead and do the head rebuild within the next couple of weeks, and wait to do the pan gasket and whatever else in the bottom end at a later time.
bwallen149- Just out of curiosity, when you have that super low oil pressure what does the reading show on the stock oil pressure guage? Just wondering. Thank you sir.
- Thread starter
- #10
Well, I would agree it is super low, but 4.2psi is minimum @ idle according to the fsm. But, the stock gauge reads basically nothing, it does move when you turn the ignition off. It is on the bottom mark, maybe half the needle above the bottom mark.
Huh. Thats a bit lower than mine at idle on a really hot day after a long highway run. Usually its right in the middle at idle, then at the top hash on throttle.
