Hello All,

I have a 1964 98 oldsmobile with a 394CI engine. The engine runs smooth without any noises. The engine has many oil leaks, so I have taken the motor out and i have it in an engine stand. My plan was to simply replace all gaskets, except for the head gaskets.

My neighbor stopped by and suggested that given the car has 94k miles, I should probably do the heads, and change the valves to valves that can handle unleaded fuel. He also suggested to change all freeze plugs and at the minimum replace the main bearings.

I have never rebuilt an engine myself, and I am wondering it it is worth messing with it and realistically how much money it would cost to do:

Heads with new valves (parts and the labor)
Replace main bearings (parts and the labor)

Any advice would be great, as i said just trying to decide if I want to spend the money fixing something that aint broke but potentially might break in the future (this is just a weekend car)

Thanks

 

Earlier this year I bought a 77 olds 350 for my cutlass off of craigslist that had been sitting un-used for over 20 years. I replaced the oil pan gasket, the intake gasket and the exhaust manifold gaskets. I didn't replace anything else, besides spark plugs and wires etc.. I took a chance on it based on how very clean it looked when I took the valve covers the intake and the oil pan off. It started right up and I used it all summer with no problems or leaks. However I knew this engine was going to just be a band-aid until I rebuilt my original or I would have had it rebuilt. So I think most guys on here are going to tell you to rebuild it as long as you have it out of the car, and are planning on keeping the engine for regular use in the vehicle. I hope none of you regular guys take offense to me giving my 2 cents, just sharing my small experience.

 

Me, I would rebuild because I know with my luck the engine would eat a valve or throw a rod within 100 miles after reinstalling. I don't know the cost on your engine. It seems to me the labor involved is the biggest expence.

Larry

 

I think it all comes down to your pocketbook.

I was planning on just doing the minimums on my latest engine, but the more I thought about it, I was penny pinching for no real good reason other than keeping the wife happy. What I DONT like doing is something twice. So, I reasoned with the wife that we would be wasting money since I would likely need to rebuid the motor down the road if I did a budget ring/bearing job versus full rebuild. Wife agreed so I am going down the full rebuild route now because we dont want to do this twice.

regarding head work to handle unleaded fuel, it depends on how you drive. IF you are a moderate driver and never really hammer on the engine, your valves will be fine. If you run the engine under load (like a boat motor) and/or race it occasionally, then you should probably upgrade. Its prolonged exposure to high heat that wears down your exhaust valves.

 

Eh. If it works, don't fix it.

Clean it up, change the gaskets, get a good look inside, so you know if you've got any problems brewing, then drive it 'till you're good and ready to rebuild it.
You could have another 50,000 trouble-free miles left in that thing.

- Eric

 

Oh, and a full STOCK rebuild, no frills with standard stock parts, is around 2200 for an assembled long block.. just got the quote yesterday for my 455. Add a few MAW's in there, and realistically a rebuild will run you between 3000 and 5000.

 

You sort of skipped very important tests to determine engine wear: 1) compression test, 2) leakdown test.

Compression test is the most critical and will provide an indication of wear in the top end. Leakdown tests will give more specific information as to cause of any low compression. Read up on these tests if you are not familiar with them. What you're looking for is even compression across all cylinders even if it is below new engine specs.

You need to be able to turn the engine over to do these and it will be a two person job with the engine on the stand. Hook a battery to it, short across starter terminals to engage starter. Pull the plugs first and do the compression test following recommended procedures.

If you have even compression readings (within 15 psi or so) on all cylinders I would replace leaking gaskets, button it up and drive it until it actually failed.

I'm not so sure your neighbor is giving good advice on two points. First on the valves it is usually the valve seats that are replaced to accommodate unleaded fuels, not necessarily the valves. Second, I wouldn't assume the bottom end ( crank, cam and associated bearings are necessarily bad. Particularly if you weren't getting knocking in the lower end.

If you decide to redo the engine and you have no training or tools for that I would try to source an already rebuilt long block from a reputable shop. you would re use the manifolds, starter, carb, generator etc. from your old engine. Others may have different opinions. I am certainly not the guru of engine machining, assembly etc.

 

Hello All,

I really appreciate your honest advice. I will do a compression test by putting bakc the starter and removing the plugs and see what readings i get.

Any risks on the ehngine trying to fall off or anything like that by doing the compression test while the engine is mounted on the engine stand?

 

Probably not much risk if you have a quality engine stand. But since you obviously have a cherry picker that you pulled the engine with, I'd hook it back up to the engine and put just enough tension on it so it would act as a back-up if the stand failed. I've spun engines over on my shop floor that were only braced with wood 4x4s without damage or mishaps. Just take care to position yourself safely at all times.

 

If the engine is leaking at the rear main seal it would be a good time to replace it while the engine is out of the car and the oil pan is off. While doing that you could easily check the bearing clearance on the rear main bearing to make sure that it isn't ready to fail.

 

I agree - Pull some bearing caps and check while you're there. You can also get a good look at the bores from underneath.

Regarding the compression test, I've done compression tests on the stand - engine wobbles a little, but should be fine. If the hoist is available for extra support, I agree it's a good idea to hook it up, just as a precaution.

But, ask yourself: If it's got iffy compression in one cylinder, but it runs fine, are you gonna rebuild it or are you gonna put it back in and run it 'till it breaks?

- Eric

 

To replace the main seal you have to pull the #5 cap.

The Voice of Experience says
"Inspect every one of the main and rod bearings while you have it apart"

Not some of them.

Yes, do ALL the freeze plugs while it's out.

If bearings look OK, and compression is fine, button her back up.

If the bearings look a teensy bit iffy replace the bearings and call it good.

If they look really bad, THEN start to delve deeper.

 

No argument here.

I guess I was trying to soft-pedal it. When I've done it, I've pulled them all - it's no big deal to do.

And I agree with your advice, too - if they look good, just back away and put it all back together.

- Eric

 

If it was me I would pull the heads also. The factory head gaskets are steel shim and being that old, I'm sure they are rusting and ready to go.
Be sure to price what all you need to do. It will be a little more difficult to find parts for the 394 engine. Be sure to spec 63/64 394 for there are differences from the 59 to 62 394's
Also be sure to keep all the lifters in there respective cam locations, do not mix them up. Also a new oil pump is a good thing..

Gene