I just pulled out the 390 in my truck because the retarded rear main seal refused to go in. So after doing all this work I need to decide what to do. Should I get a new engine or replace the rear main and oil pump on this one? Here's the situation:

Monday I was driving down the road when my oil pump froze up and I lost all oil pressure. I did not notice the light or the tapping until I had driven probably a little less than a mile at 2,000 rpm. After that I started it three more times thinking the problem was just low oil. I don't THINK I hear knocking; just tapping lifters. The engine is all original (1969) and has about 130,000 miles on it. When I pulled the pan I was shocked at how clean it was. There was no sludge and everything was clean. Last I pulled the valve covers I noticed quite a bit of carbon buildup. It does burn a little oil but it is only visible on a morning startup or if I get it up to 4,000 rpm (I don't do that often). It does have some blowby. It gets horrid gas mileage even with a ignitor ignition box in the distributer and an original rebuilt carb (or a new holley rebuilt ). I have never checked the vaccum. Last I checked the compression (8,000miles ago) it had 120 psi on all cylendars except #8 which had 90psi. I am a little worried that there are some internal vaccum problems since it is a bear to start when cold no matter how well tuned the carb and distributer are. It has no vaccum leaks due to gaskets either. I hear piston slap (maybe it's sparkplug knock) if I stomp on it without down shifting to pass someone, but I never hear it any other time. As for the condition of the bearings, I have only looked at the rear main one which is somewhat worn; the piece in the cap has a copper colored area.

A year ago without a doubt I would buy a new engine, but I am going to go to a really expensive college in a few months and I don't really want to buy an engine. However, I use this truck for work and will use it during the weekends while I am still in college and during the summers. So, I can't afford to come home to a dead engine some weekend. (I mow lawns so I would be screwed if this were to happen). If I stick with this engine I am not going to replace anything but the rear main, pan gasket, valve cover gaskets, and oil pump. If I start doing stuff like head gaskets and bearings then I am just getting closer and closer to a rebuild, and I don't have time for that.

So, what should I do? Is this engine going to last for the next 5 years (probably less than 30,000 miles)? What are the chances that the engine is already ruined?
Please let me know what you think soon because if I go with a new engine I need to order it tomorrow morning.
thanks for any advice
brad

 

What made your oil pump freeze! Did you destroy the shaft that drives it? It dosen't sound like putting new gaskets on it is going to make it last any longer. You might consider a valve job!

 

I am not sure what made it freeze. It's probably just worn out after 130000 miles. I pulled it out and it won't spin, and the drive shaft was snapped off. Of course, I wouldn't just put new gaskets on it, I would also replace the oil pump.
I won't do a valve job, it'll take too long and I may as well just get a new engine at that point.

 

I'd slide new bearings in it, stick an oil pump in and run it. It'll go as long as the bearings and rings are in good shape and everything else holds together.

Since it's out, you may as well put new rings on the pistons as well. Always helps.

 

Like I said, it will take too long to do anything other than what i have listed. If I put new rings and bearings in, then I may as well do a full rebuild.

 

replace the oil pump shaft and be on your way.

 

I would pull the oil pump apart, and see if you can see what made it freeze up probably a piece of something in it, if it is , and you don't see any others then you probably are ok to replace it, and go, but a good guess would be a piece of a valve seal, so you might want to check those, and maybe replace them (this can be done with the heads on the engine

 

I would also recommend this route, as long as the bearing journals are all in good shape, with serious no scratches or grooves. New valve seals may fix the oil burning problem.