Main and Rod Bearings

I recently acquired a 65 BJ8 with 65K miles on it. It has relatively low oil pressure. Start up around 50 #, engine hot idle 15 #, 2500 + rpms about 25#. Relief spring and valve are new and the guage is correct. The rocker arm assembly is in good shape. I suspect that the rod and main bearings are worn. My Haynes manual suggests for long engine life to change the big end bearings at 30K intervals and mains at 50K. It goes on to say that this should insure a long crankshaft life.
Anyway, my newbie question. Can the mains and rod bearings be changed without pulling the engine?
Obviously, I would mic the crank to insure its specs. I suspect that the rod bearings can be changed, but am unsure about the mains and the thrust washers. Actually I have never look inside a Healey engine. By the way compression tested around 150 on all cylinders.
Thanks.

Hi & welcome to the forum,
Not sure what to say about the low oil pressure. You should be using a SAE 20W-50 oil. It could be worn bearings. It could also be a worn oil pump. I think 150 is a little low for compression on this engine. Maybe everything is worn a bit. Do a little internal checking before replacing the bearings. Remove the rod & main bearing caps ONE AT A TIME & check clearances with Plastigage. Wipe as much oil as possible from the bearing shell & the crankshaft before measuring. Re-oil after checking. The clearances should be no more than 0.002". Check the oil pump clearances against book specs. I believe 0.002" again.

Are you "sure" that the rocker arm bushings are not loose. With the engine hot & idling, there should be no more than about a drop every second from each rocker arm.

If bearing clearances are excessive they can be replaced as a last resort. The bearing faces will show wear marks, color changes, copper exposed, if they are seriously worn.

Bearing inserts usually have a size etched on the back side. Standard will have no size. Ten thousandths undersize would be marked .010 & so on. Replace with the same size. It is fairly easy to change the rod bearing inserts. All surfaces must be spotlessly clean. One piece of grit in a bearing will result in disaster.

The main bearing inserts can be pretty much changed in place but it is kind of tricky. Basically you remove a main bearing cap, turn the crankshaft to where the oil hole is exposed, insert a small tool, T shaped, into the oil hole so that it catches the edge of the bearing insert, & turn the crankshaft to roll the insert out. Some folks use an appropriate size cotter pin with the round top flattened to make a tool. The top of the T must be thinner than the bearing insert. There is a locating tab on the back side of the insert so the bearing will only roll out when the crank is turned in one direction. It shouldn't take very much force to roll the inserts out. This whole process is kind of risky if you haven't done it before.

Check each of the newly installed bearings with Plastigage again as you install them to make sure that they have 0.001" to 0.002" clearance. Then remove them & apply a good assembly lube & install again. Above all, don't take any shortcuts on this procedure.
D

I would rather remove the engine and have it on an engine stand. This would enable you to have the crank checked,polished or turned if needed. also there are measurements fore and aft that need to be taken.
This also would be a good time to install a rear main seal kit if your engine doesn't have one already.I would have the oil pump checked or replaced also. Also cam bearings can cause a loss of oil pressure as well as the rocker assembly. When I removed my rockers I was surprised how much wear was on the shaft. Bob

I would not waste my time changing main and rod inserts in place without going farther and measuring the crank carefully and regrinding if necessary. I doubt if you will find much improvement in the oil pressure from just changing the inserts and leaving worn journals in there.

Better yet, drive and enjoy your car. Your oil pressure sounds fairly normal to me, my 100 has had low oil pressure when hot (about 25 psi, give or take a few) for years. We have driven this car many enjoyable cross country miles this way. I use 20W-50 oil, but it isn't much worse on 30 wt.

My rear "seal" leaks a lot (hey, it's a Healey). This might be improved with new crank grind and inserts, but for now it does not seem to be worth the trouble to me.

I would wait until you start to hear a few rod knocks or she starts smoking or won't hold compression before you go after the bearings. Then you can do the entire job right, remachine the bores, crank, valves, rockers, everything....

Your car sounds like a good runner with lots of life left on that engine.

Enjoy!

Bill.

If you wait until you hear rod knocks, you are close to disaster & the crank will for sure need regrinding. A whole lot of work & expense. Correct use of Plastigage can tell you a whole lot about crank journal condition without disassembling the whole engine. For example, if with a new insert installed, it shows more than .0005" taper (end to end/side to side variation) or more than .002" clearance the crank is worn & should be reground. The checking is relatively cheap & easy to do. If you go further, there is really no stopping point until the engine is totally rebuilt. The choice is yours to make.
D

The PO had the rocker arm rebuilt not long ago. With the valve cover off and a hot engine, the drop per second of oil from each rocker seems to be what I am able to see. Certainly no sqirting up of the oil.
Now if I can talk my friend into using his lift, I will pull the oil pan and examine the bearings and check with plastiguage. I assume the major suppliers all offer bearings. Is one brand better than another? If I am unable to use the lift, I might have a shop do this for me. I don't think there is enough room with the car up on blocks. Well, there probably is, but this old geezer doesn't like crawling around under cars that much anymore. Incidently, the car runs very well except for the low oil pressure. Engine noise is quiet as well as the water pump. Of course, the exhaust has the Healey sound. The only unusual noise seems to be from the original generator, which probably has some bearing issues of its own.

Healeynutt:

If you plastigage like Dave suggests, I agree it is not too big a deal. But I think if you took your car to a professional mechanic for this work, it would probably be a $500 to $1000 job. It is simple, but there is a lot of time and effort to get access to those bearings. If you learn that new bearings are needed (your bearings will probably not be in spec, the car has 65K miles, and the oil pressure is lower than it would be for a freshly rebuilt engine) then removing the crank and getting it ground will set you back another K or more.

To go through that for an engine that is quiet, runs well, and the only problem is 25psi oil pressure on a hot engine seems like paying a lot for little. Why not enjoy the car and wait for either the oil pressure to get lower or other issues such as oil consumption, noises, etc warrant opening up this engine? Based on my experience, this is not taking a big risk with your Healey. They are known to have relatively low oil pressure with age yet they don't tend to self destruct suddendly from bearing failure.

ps there have been other posts describing a vane oil pump as a way to deliver more oil to the bearings. Just changing out the oil pump is a bit simpler and may make you more confortable with the car.


Bill

[ QUOTE ]
The PO had the rocker arm rebuilt not long ago. With the valve cover off and a hot engine, the drop per second of oil from each rocker seems to be what I am able to see. Certainly no sqirting up of the oil.
, the car runs very well except for the low oil pressure. Engine noise is quiet as well as the water pump. Of course, the exhaust has the Healey sound. The only unusual noise seems to be from the original generator, which probably has some bearing issues of its own.

[/ QUOTE ]

Keoke says ,being an old BJ8 owner-let it alone its just fine when it needs additional attention it will tell you so.---Keoke-- /ubbthreads/images/graemlins/yesnod.gif

One other thing to check first. Reduced pressure can be caused by a sticky or leaking pressure relief valve, and or it's spring may be weak. This problem will usually show up as low pressure at idle & moderate rpm. Remove the relief valve cap, spring, & plunger. Polish the plunger sides with Crocus cloth. You can often tap the plunger into it's seat with a wood dowel & hammer. Rotating the plunger a bit as you tap. Replace the spring with a new one, stretch the old spring a bit, or put a 3/16" long spacer between spring & cap. If the spacer is longer, it won't let the plunger travel far enough to release excess pressure. If these easy remedies don't work you likely have a worn oil pump or bearings. My BN2 went from 20 psi hot idle to 40, & from 50 psi to 60 psi at 3,000 rpm & above.
D

[ QUOTE ]
One other thing to check first. Reduced pressure can be caused by a sticky or leaking pressure relief valve, and or it's spring may be weak. This problem will usually show up as low pressure at idle & moderate rpm. My BN2 went from 20 psi hot idle to 40, & from 50 psi to 60 psi at 3,000 rpm & above.
D

[/ QUOTE ]

I wonder how many thousands of bucks have been spent because of this condition? I shimmed mine with a nut approx. .30 thick that fit into the plunger shimming the spring. The effects were about the same as Dave experienced.

Dave and Michael, "the relief spring and valve are new" However, I would try cleaning the seat up or shimming the spring to raise the hot idle pressure to a more respectable value. It may even be that the valve is not correct for the BJ8 which usually causes a lower pressure reading without shimming.---Fwiw---Keoke ?