I completed total rebuild on my '25 171 four. Rod bearing failed after 20-25 miles while climbing a steep hill. Please share any insight into engine lube system and clearance between rod bearings and crank pins. This system seems problematic. Pump showed 3 lbs. cold 0 lbs. warm. Rods are being rebabbitted now. Thanks....Paul Chapot
indicate either a worn pump or problem with the piping or gauge. That does not indicate enough flow to the main bearings or dipper troughs.
Did you use oil or assembly lube on the bearings when they were assembled? Did you add oil to the lines prior to starting the engine to get the oil pump primed? Did you crank the engine over to indicate oil pressure and fill the main bearing reservoirs and rod troughs prior to starting?
If you use rods with old babbitt they could have had cracks that were not noticed.
The rod and main bearings should have an initial clearance of ~ 0.001". Greater than 0.0025" particularly on initial startup of a new engine is too much. Babbitt is relatively soft and will "relax" a bit on initial running. I have found the procedure in the Repair Manual to be the best in setting clearances. Plastiqauge does not work for me other than getting a general idea of the approx. clearance.
All answers are yes. Plastigauge showed 0.002 -0.003 clearance. one other item I did not mention. At nipple to the center main bearing there was a 1/8" tube soldered to the nipple extending 2" into block. Since it was soldered to a nipple that was not original, and since all bearings were new, I did not reinstall. does this constriction at center main supply boost pressure. Thanks.....Paul Chapot
My experience has been that Plastigauge gives incorrect clearance measurements with babbitt bearings. It tends to indicate a tighter clearance than actual. The best way to set up clearances is use the method in the Repair Manual. Basically it involves taking out shims until the bearing locks on the journal, then add back a known thickness of shim(s) to give 0.001" clearance. On rods the final tightening should give enough resistance to not be able to move the rod side to side on the journal by hand. Light taps with a small hammer should move the rod side to side. Any clearance over ~0.0025" will result in a oil leak from the rear main.
Chipper, I just rebuilt my 25 engine and am having oil pressure problems also. The engine had great oil pressure before the rebuild. I primed the oil system by squirting oil in the oil pressure gauge fitting. I still had no oil pressure so I removed the oil pan and started checking things out. I removed the oil pump and put the pick up tube into a cup of oil and turned the oil pump with a drill. A good flow of oil came out but I was not sure it was enough. I went back to the engine and squirted oil into the fitting again to see where the oil came out. There was no oil coming out of the oil pump line or any of the four oil trough lines. All the oil was running out the bottom of the what I call a manifold into the the center main bearing reservoirs. I couldn't see the bottom of the "manifold" to see where the oil was coming out of so I too the manifold and four lines out of the engine. Upon seeing how it was made I saw that directly below the oil pressure line fitting that manifold has an open circle with a bar across the center of it. So now I see that all my oil is coming out there and not making it to the 5 oil lines. Should there be something to impede the amount of oil coming out of the bottom of the manifold or should there be enough oil pressure to the manifold to come out all the lines and the reservoir filler? If so then I guess I"ll have to purchase a rebuilt oil pump which after the amount of money I spent on this rebuild won't be easy at this time. Any help would be great. Rick Alter
l just went thru school is in session again. It is the oil distributor valve that is giving me problems. My engine is a 25 so a little different than the one discussed. I have no oil filter. I got the engine block back from the rebuilder with the oil pressure fitting separate and nothing down inside the valve to direct the oil where to go. Is there a possibility my valve is missing an important part>
Just a suggestion: Even though your truck is a '25, the engine block is a '26, so when asking technical questions, it is important to clearly identify this. The oil pump and distribution assemblies are very different between the '25 and '26.
As you've observed, oil squirts out the side of the oil distributor. This stream of oil is meant to drench the middle main bearing with oil because this bearing acts as the thrust bearing. Here is a thread that discusses oil pumps that you might enjoy: Oil restrictor and oil pump tests
Thanks for the great info. The cast number on the block is L 13 5. So I just assumed it was built 12/13/25 but since it's so close to the end of the year it must be as you say a 26. I also just got off the phone with the guy that rebuilt the block. He found a 5/16" x 1/2" spring/diaphragm in the screen of his parts washer and is mailing it to me. Hopefully it is what I need for the distribution assembly.
I thought I would upload some pictures so we are all on the same page. This is my first upload and it looks like it worked! Included a picture of the engine about ready to run.
I bought an old used oil pump off Ebay to see if it would put out more volume that the pump I have. Using my drill to spin it nothing comes out. I haven't got the part my engine rebuilder found in his cleaning tank that I suspect goes in the oil distribution assembly yet but would like to get a step ahead and make sure I have a pump that puts out enough volume. Can someone tell me how much oil should be coming out using the drill to spin it? I'm getting anxious to see how this engine is going to run. Thank you in advance.
The vane type oil pumps need to be primed, they won't suck the oil up into the vanes on their own. Every now and then, I'd start one of my trucks and show no oil pressure, so I'd prime the pump. To prime them, I loosened the oil tube that goes into the top of the oil distributor (this tube goes to the oil pressure gauge) and squirted some oil into the distributor. I figured from there, the squirted oil would drain down to the pump and prime it. This seems to work because when I started the engine again, I had oil pressure.
BTW, nobody makes replacement vanes. GM started offering the gear-type pumps as replacement parts for the vane pumps.
Although I was getting 10 psi out of the old oil pump in Lurch's engine, when I did the rebuild I decided to go with a new gear-type pump because I was not willing to risk the $2K I put into rebuilding the engine on the old pump.
If you want Lurch's old oil pump, you can have it for the cost of postage.
Lemme know.
Dean
Dean 'Rustoholic' Meltz old and ugly is beautiful!
I see in the engine rebuild class document there is an oil distributor valve assembly which I don't have. Hopefully what the engine rebuilder found in his tank is what I need. Should be here tomorrow.
Someone please help. Attached are pictures of what the engine rebuilder sent me. It is too small to be the oil distributor valve assembly I need. Is it possible this is part of it and something is missing? I attached the pump to the oil distributor and put my finger over the hole in the bottom that allows oil to drain into the reservoir for the middle main. When I run the pump with my drill an ample amount of oil comes out the four trough tubes. When I unblock the hole, all the oil comes out there and none to the tubes. I am almost positive I am missing part or all of the oil distributor valve assembly. If anyone could shed some light on this problem I would greatly appreciate it RIck
That doesn't look right to me, this link should take you to the owners manual page that describes the way it all works. Klick 'next page' at the bottom of the rest.
I have Gary Wallace looking into it for me now that he is back from vacation.. My valve is different than Deans and the one Bernard shows in the owners manual has and oil filter and I do not. Hopefully someone can shed light on my "different" valve assembly.
It looks like Gary Wallace came through for me again. He sent me this picture of the valve I am missing. I remember seeing it months ago so the search is on. For those of you who would like to see the valve that is used without an oil pump here it is.
The '28 engine came with an oil filter and the spring valve in the oil distributor was in place to counteract the possibility of a clogged filter, thus making sure that oil is still pumped to the four trough filling tubes even if oil flow stopped going through the filter.
I believe the 1926 engine did not have an oil filter, This might explain why your oil distributor is different than the one I worked on.
I suggest the following:
1. Send an email to the Technical Advisors that are listed in the G&D. Make sure you tell them that you have a '26 engine in a '25 truck.
2. Search the membership database for other folks who have a 1926 Chevy. I recently discovered that the database search function looks at the list of vehicles, in addition to name, address, VCCA number, etc.
Hope this helps. Dean
Dean 'Rustoholic' Meltz old and ugly is beautiful!
Dean, I sent out several emails using the database. I did get one answer but he had a different engine. My X series engine used the type of oil distribution valve that was used only in early 1926. Gary Wallace has mailed out a new valve, but did not have the spring. I guess will just have to experiment to find out which spring tension will work for me. As soon as I get oil moving it will be time to crank this engine up! Thanks to everyone for their help. Rick
If you wanted to,you could always try an install the 1927 oil trough distributor(the pressure relief valves are the same from 1927 to the mid to late '30's?,as one of the problems the plunger type of valve in the '26 engines was that the plunger would stick in its bore if the plunger was jammed up by any rubbish in the oil,and give either a "0" to extremely low oil pressure reading.You may have to block off the oil filter return pipe fitting hole if you decide to use the '27 trough feeder.
