I have removed my previously rebuilt, (early 80s) 71 455 in order to replace motor mounts, repaint, correct mismatch of water pump and pulleys etc., exhaust manifold change and to replace the rear rope seal which has started to drip.
As a background, the engine runs well, with good power and is quiet. I did a compression test and they range from 175 - 185 except for no 8 which is 190. Oil pressure has never been real high 45 or so even when cold on 5 w50. It never drops below 15 or so hot in gear. So, when I removed no. 5 bearing cap to start on the seal, the bearing was showing some copper, and I removed the rest of the main caps and all are showing copper with the exception of No. 1. So I am now into taking the crankshaft out and all the work that entails. I read in the CSM about removing the crank, and have removed the rod caps and installed hoses on the bolts to act as protectors. It shows using rubber bands and oil pan bolts to position the rods for installation of the crank. I have started to remove the crank, but it is fairly resistant with hoses being up against the crank. I need advice, first of all, in removing the crank. Can I push the rod and piston up into the cylinder to help alleviate pressue between the hoses and crank or just pull hard and all should come out ok? I will take the crank to the machine shop to have it measured. If the it checks out ok, I presume I would buy std. bearings and put it back together and clearances should be fine. With this method it's very difficult to check clearences and spin the crank as the rods are in the way. I would also replace rod bearings at the same time. If a crank needs just polishing, are there bearings available to compensate for some removal of material? Someone told me there are standard plus .001 available.
So I'm struggling with this partial teardown, vs. a total teardown which otherwise doesn't seem warranted. Am I setting myself up for potential problems or should I be OK? I really don't want to go further than I have to.
Opinions and suggestions will be most welcome. Thanks.

 

I would have plastigauged each of the bearing first before removing the crank. To make sure they are out of tolerance.

 

How many miles on the engine ? How much clearance do you have on the bearings ? If the crank is polished, it won't remove enough material to notice.

 

before you do anything pull the main bearings and look on the back of them to see if it has a size on it.it will either say std, 001 .010,.020 or i have seen .0005

 

IMO you're in it this far why cut corners? A light machine job on everything vs major machining on a failure is not the right way to go. This is a bad time to live in Economy, Nova Scotia ey?

Yes if the heads are off...tap the pistons up in the bore to gain clearance on the crank. Use a dead blow and a stick of wood. If the heads are on be careful to avoid harsh piston to valve contact. A gentle pry here and there on a crank weight it should pop out. Make sure you keep all caps and fasteners in their original positions...that goes for top end parts as well.
Platigauge is a quick check. If the plastigauge finds a problem then its time break out the proper metrology tools(which a good machine shop will have).

A machine shop competent with Oldsmobile (keyword) will inspect the parts which will need machine work and tell you(quote you) what needs to be machined. Do the cam bearings, cam, lifters, valve guides, port clean up, new timing set etc...usual cast of characters when machining an engine. She'll go another 35 years worry free.
Consider switching to the Ford one-piece rear main seal.

Let the MAWs commence! Trans, converter, engine bay detail, frame removal et al...

Get a copy of Bill Trovato's book on Olds engines. At minimum, he can guide you with solid tech answers and even help source high-quality parts.
http://www.btrperformance.com/contact_us.html

Steve

 

 

The crank is still in the engine, so can I use plastigauge between the top of the crank and the main cap to get a true idea of existing clearance or does it need to be under the crank to the block?
I don't know how many miles on the engine and I'm always skeptic of engine builders in N.S. with experience with Oldsmobiles. It's all a dilemma. I have Bill Travato's book which is certainly helpful, but it's hard sometimes distinguishing between what's acceptable on a stock rebuild vs. trying to build a 500 hp engine and keeping it altogether.
I understand the clearances on the mains should be .0025 - .003"? With these clearances, would a high volume pump compensate so you don't need 50 weight oil?
I just detailed the transmission and resealed it, along with rebuilding and installing a tilt wheel column, rebuilt the carburetor, and detailed the steering box and driveshaft, so this is the last mechanical job.
Hopefully a plastigauge check will provide more insight.

 

Look up how to use plastigauge, it should be between the top of the crank and the bearing on each of the main caps.