VCCA Home Forums TECHNICAL - 1945 AND NEWER 1965-1970 Strange problem with 1966 250 engine C30 one-ton

Hi everyone. It is nice to be back. I was registered previously as "Lee Prairie" or "Lee_of_the_Prairie". I tried to get this website to send me my forgotten password perhaps a hundred times. Something is wrong with this site. In all the attempts, I never received a reset password or anything from this site. So I had to re-register with a new name.

I am restoring my dad's 1966 Chevy C30 one ton truck. I was 14 when he bought it and I am the second owner. I have done a lot of work on it - it runs great now. Two things under the hood that are NOT new are the engine block and the alternator. I have gone through it and everything works fine. Except........

Please don't tell me the head is cracked because it isn't. I have had the head off 3 times and had it magnafluxed all three times by three different machine shops. There is nothing wrong with the head. Please don't propose that. I have replace the head gasket 3 times as well. Felpro. The Felpro instructions are to NOT use a gasket sealant so I didn't. There is NOTHING wrong with the head and there is nothing wrong with the head gasket. So the knee-jerk response (that the head is cracked or the gasket is bad) is dead on arrival.

I have oil in the water. The truck runs fine, but I get oil in the water. The engine cooling system is pressurized so it is even doubly curious how oil gets in there. The oil that goes to the head is NOT pressurized. The rockers oil via hollow push rods. That oil is not under pressure from the oil pump. The oil that oils the rockers comes through the push rods from the cam followers and the oil gets there just from the force of the system moving. It isn't part of the oil pressure system.

A machine shop proposed that when the water pump was replaced, the dolt that did it (not me - before my time) screwed the long bolt into the short hole and ruptured the cylinder wall below the piston rings. Well, I don't believe that either. I took all the bolts out and they were all pristine. None of them had damage to them that would have occurred if the bolt had been screwed in against the cylinder wall (water jacket side) until it broke the water jacket / cylinder wall. I don't buy it.

The oil pressure guage always registers 30 psi. The pressure in the cooling system is always 5 to 10 psi.

So, where can the oil be getting into the cooling system?

Any intelligent suggestions will be greatly appreciated, although suggestions that the head or gasket is faulty will be ignored.

Many thanks,

Lee Prairie

Are you losing water level in the radiator?The car run fine.? Spark plugs are equally clean? Drive it til it drops. If the block is cracked between the cylinders you could see oil. blue38

Consider this: Okay, the water is under pressure, but at what pressure? The oil is under pressure at 30 lbs, your figure, so the oil will easily overcome the water pressure and you have oil in the water, and not water in the oil.

So the solution is to discover where the oil and water are near each other where one could enter the other. And I didn't say cracked head or leaking head gasket.

Thanks, guys - chevradioman, I bought a radio from you for my '49 Chevy 4400 (ton and a half) grain bed truck.

I have tried to find an oiling diagram for that engine (1966 Chevy 250 long block inline 6) in order to know where the pressurized oil is close to the water. It's making me nuts. Any suggestions?

This problem first occurred back last fall. I believed I had a head gasket failure when suddenly I had water in the oil and oil in the water. It was too cold to work on it then so I drained all the fluids and waited until spring to start the overhaul. Head has been refurbished and the gasket replaced 3 times now. At present, there is no water in the oil, but there is oil in the water. Thre main and rod bearings receive pressurized oil, but I believe those are the only places where pressurized oil is delivered.

What is the "oil pressure" in the oil pan and below the cylinders when the truck is going down the highway at 50 mph? In the old-style splash systems (this one is not a splasher) most if not all the oil is flying around inside the engine rather than sitting in the sump ready to be pumped. In the pressurized oil engines like this 250, the oil flying around below the cylinders as the truck is running should generate some mechanical, non-oil pump oil pressure below the cylinders.

I agree that somewhere the oil pressure is overpowering the water pressure. But where? I would rather fix it in-situ rather than pull the engine and take it completely apart in an effort to find a possible crack in the block.

Thanks - does anyone have a good idea where the oiling system has pressure? As I mentioned, the oil that gets to the head is not pressurized. At least not by the oil pump.

Thanks,

Lee Prairie

P.S. Why not fill the cooling system with oil and just forget about it? The early tractors used oil as an engine coolant fluid. Oil is lighter than water and so the engine would probably run hotter. But is that bad?

Lee

At any time when you had the head off,did you check the block deck to see if it was flat?If you had the head re-done they probably decked the gasket surface to ensure it was flat.I had one big block chevy that had a difference of .065 across the deck surface.You could check it with a straight edge and feeler gauges,but the head must be removed again to do that.If the truck has an automatic transmission,the trans fluid line that runs through the radiator could be cracked or eroded which will mix the two fluids,not oil but trans fluid and water.

Thank you, Mike - I did not check the flatness of the block deck. I've been thinking of that as well. I have a nice metal straight edge. I've been thinking about doing that this weekend....

Lee

As an update ... I am watching the oil very closely - first so that if any water gets in the oil I can catch it quickly and secondly, so that the oil level doesn't get low.

So far I have no water in the oil. There is still some oil in the water, but I'm not losing much oil and what I do lose could be leaking from the rear crankshaft seal, which I know is leaking. I'm having fun driving it and have taken it on relatively long trips with success. I'm running Blue Devil in the water system JIC.

The truck runs like a dream and it is hugely fun to drive. It was my dad's truck. Of course he never let ME drive it while he was alive. I almost have it up to 40,000 miles now. When I bought it from my step-mom it had 33,000 miles on it.

When I had the head off (three times), I should have ringed it, but I didn't because it doesn't smoke and the inside of the tail pipe is white. But the oil gets dark quickly.....

Lee Prairie

For some reason I missed this post prior to today.
The 7 main bearing engines did not have anthing oil pressure lubricated above the crankshaft and cam shaft. The oil to the rocker arms was pumped through the lifters and up through the hollow push rods to lubricate the valve train. The oil then flowed back to the oil pan and was not under pressure. This means that it would not be possible for the head/block surfaces to interchange oil and water.
If oil is being pushed into the cooling system it is possible that the block is porus due to rust as these blocks had thin wall casting.
The oil is thrown off of the crankshaft on a full pressure oiling engine. Oil is constantly passing by the connecting rod bearings which are under high pressure. With this type of oiling system oil consumption will (may) increase as the rod bearins wear and the clearence increase and more oil it thrown onto the cylinder walls.

Thank you, ChevNut. I've run the engine without the valve cover on it and it is obvious that the oil that lubricates the rockers is not pressurized and it simply runs back down to the crankcase.

If there is a porous place, due to rust, in a wall between the water jacket and the crankcase, and since the water is pressurized and the oil flying around inside the crankcase isn't, why wouldn't the flow be in the other direction (water going into the oil)?

Thanks again!

Lee Prairie

Have you tried a Stant or other brand of cooling system pressure tester. Pump it up to 15 to 20 PSI and take the oil filler cap and listen for air or bubbling water. Remove the spark plugs and listen to individual cylinders. Try this cold first and if you don't find it bring it up to temperature and try it again. I have had very good success with this. Good Luck, and Merry Christmas!!!!

You're answering to a comment that was posted 3 months ago. I'm betting the problem was either fixed or forgotten about, by now.

Yes, I am aware that this was 3 months ago, but thanks for pointing that out, it gained you another post. I seen no follow up or good solution for this gentlemans question, so for him or others that have the problem in the future I thought I might give a little insight. But thanks again for pointing that out as I might have overlooked the post date.





P.S. I was under the impression that this forum was for imparting knowledge to create a knowledge base that could be searched for similiar problems that one might be incurring in the present. I have seen numerous references over the past 4 years to the fact that "this has been discussed in depth and search for an answer from a past post". Does that not apply to the 1965-1970 index? I hope no-one was overly put out from reading my worthless rambling for a problem that no longer matters !!

Slow yourself down ... I thought Chev Nut presented a good reply. For me, I was simply pointing out something I thought you may have overlooked.

I only get on the chat site every 2 or 3 weeks. I hardly ever look at anything other than the 29 to 32 catagory and then when I do post there often seems to be someone on this site to point out something very obvious that is seemingly to discourage me and others from posting. This is evident from the start of this post where over and over the gentleman had to state he had ran the cracked head and head gasket in ground and did not want to be told this again. The warped head or deck surface is a good possibility as is the rusted casting, but what I was offering was a way to find it. Did it matter that this post was 3 months old? You may not, but I often have 3 to 4 month periods between times I work on my old vehicles sometimes longer. From what I read, he was ready to fill the cooling system with oil in order not to have to take it apart again.
This comment was likely just out of frustration, but he obviously cares about the old Chevy and wants it fixed.

If all you were trying to do is protect me from wasting my time thanks and I am sorry, but it was Christmas Eve and I just sat down to read a few posts and decided to make a comment that I thought might help someone. Merry Christmas to you and your family Bob!!

No underhanded motives here ..... Was just trying to point out something you may not have seen.

Will not ever "do it again" in reply to your posts.

End of story on this, OK?

Merry Christmas to you and yours.