The Stovebolt Site Forums The Shop Area Engine Shop Important notes about 261 oiling system

Moderator / Editor NOTE : this thread about the oiling system on a 261 engine was extracted from another thread that went in another direction.

The information and discussion was considered worthwhile enough that I moved/merged the information into this thread here.

If it looks a little off in some places, that is why...

Enjoy.

Your friendly neighborhood stovebolt engine shop moderator,

-Woogeroo

---- original post starts below ----

Did you have the remote filter hooked up, or at least have a hose going between the the two threaded ports in the block designed for the remote filter?

Carl

Carl,

You are describing a serious/fatal necessity for only 58-63 261 blocks. They can be identified as having 1/2" NPT oil filter line holes (that were used with the "remote" full-flow oil filter).

The 54-57 261 blocks used optional by-pass (also "remote") oil filters (and smaller diameter diameter lines).

I think that 1958-63 blocks were also available without a full-flow (or, any) oil filter. Those blocks had/have a movable plug to allow no filter, or, move the plug and then require the full-flow filter line.

DFauberWoodsmith,

What year 261? What is the engine serial number in the ledge to the rear of the distributor?

What year model 261 did you get? Sounds like you did have an oil circulation problem. Best I remember the rod clamps around the wrist pin so it moves inside the piston. If it was seized in the piston then it did not receive lubrication.

First up most builders assume an engine will be installed and started right away. Assembly lube only goes so far in protecting bare steel surfaces from rust. Cylinder walls can flash rust overnight. If it was stored for months without the spark plugs in place it would be worse.

I understand feeling wronged after spending a lot of money on a rebuild. If you feel you have a good case we (Kansas) do have an Attorney General with an active Consumer Protection Division. I would be in contact with them & file a complaint.

Edit: I emailed this thread to United Engine. They should have the opportunity to respond and try to work things out with the OP if they desire. I hope it's worked out to a mutually agreeable conclusion.

3769717 Casting no identifies it as a 59-62 261 block. 3836848 head no. The rod does clamp around the wrist pin so it moves inside the piston. When we removed pistons, 2 rods would not pivot, 1 would pivot with some force, 1 had the right tolerance, and 2 sounded like baby rattles when you shook them.
Was not an ongoing lubrication problem because after it was rebuilt, it ran fine and has been running for 1000 miles. The oil lines are plugged in intake side of engine and obviously the movable pin is in the right position.

This may be irrelevant but the 261 is unique of all of these engines in that you have TWO 1/2" ports on the left intake/exhaust manifold side of the engine. The uniqueness is, if you do not connect those two together, your engine will last about 1000 miles of you are real lucky. They must be connected together! All of the rest of the engines, it doesnt matter because the oil flow is but a sample of the full flow. Also, the 848 head is NOT a native 261 head, but is a GREAT head for the 261 IF the engine shop drills two steam holes in the appropriate place. Maybe you know all of this, but the 261 engine is different in those ways.

Deve,

The importance of the 1/2" ports was pointed out near the beginning of this thread.

Also, DFauberWoodsmith posted (just before your post): "The oil lines are plugged in intake side of engine and obviously the movable pin is in the right position."

"Also, the 848 head is NOT a native 261 head, but is a GREAT head for the 261 IF the engine shop drills two steam holes in the appropriate place"

The additional coolant passages (oddly called "steamed holes" due to a Jim Carter description) that are needed when using a 235 head is not just "two steam holes in the appropriate place" in the head. Two coolant passages must be drilled in the head above each of three "siamesed" pairs of 261 cylinders (6 additional coolant passages should be drilled in the head).

Just to add to the disscussion.
...and those holes that is drilled in the "848" head should be drilled at an angle so that the holes are "SURE" to be fully into the water jacket to be fully effective. I had mine drilled at my local machine shop and if I remember correctly it was at a 12 degree angle.
.....as for the 1/2" oil ports I will be running a filter between those ports.

This one is here on the Stovebolt, but I added a few paragraphs to it:

http://forums.devestechnet.com/foru...ration-for-your-1954-1962-235-261-engine

This one was very helpful for me and many others:

http://devestechnet.com/Home/Forgotten261

I am in the middle of writing a How-To on MothBalling Engines that will be informative as well. The GO-TO people for that is the US Military. I have the Army Manual on it, and am awaiting the Navy one.

Hey, someone educate me here. What is the....... "and obviously the movable pin is in the right position."

There is a steel dowel pin in the oil gallery of some (maybe all) 261's that can be used to select either bypass or full flow filtering. If it's "out" (flush with the surface of the block) the system is set up for bypass. If it's driven in a certain distance(not sure how far) the oil gallery is blocked and the pipe-threaded ports are in series for full flow filtration. I've never tried to move the pin on my 261, but right now it's in the "bypass" position. I've heard they're VERY hard to move, with a possibility of cracking the block in the process.
Jerry

Photo from a 2009 post by hoyt about the 58-63 261 pin/plug.

http://www.inliners.org/tech/images/engine3_web.jpg

Oil Filters: If you have a late 261 with the ½" pipe thread holes on the left side, great! These engines have a full pressure full flow oil filter system. What that means is that 100% of the oil from the pump goes through the filter before it enters the engine. Maybe! Over the lower hole, you will see a boss with a dowel in the middle. If the dowel is out flush with the block, there will be a passage opened between the oil pump outlet and the main oil galley. If the dowel has been pushed in, all the oil has to go through the filter first. I don’t think I would try to move the dowel either in, or out. I would be afraid of breaking the block.

Hmm where have I heard this before? LOL! So mine is pretty darn flush with the outside of the block, yet it looks exactly like the one in the picture. Does that mean my nice spin-on external filter will only get a sampling? I have already tested and it gets nice oil flow to the rockers.

I added that to the How-To so it's there now. Sort of important don't you think? Yet it's nowhere in the shop manual for that engine!

Jim Carter provides some partially correct (and incomplete) information about the 58-63 261 (USA Chevrolet truck) oil system in the information of his that you posted on your website (near the end of his "Forgotten 261" page).

Yes, I added some more material now. There is a pretty decent write-up at inliners which I referenced as well. I called two engine shops today that specialize in these old engines and neither of them knew anything about the pin. Its so low on the radar I guess, yet seems kind of important to me. Does it strike anyone else as kind of a hokey thing? I mean if its pushed in, and you want to pull it out, no way to do that from outside. Then seems leakage would be a problem with a higher psi oil pressure since I assume there is no seal around the pin.

Interesting stuff. This is what I added. Please tell me if it needs more because a COMPLETE how-to is great, but an incomplete one can send someone down the wrong path and really cause problems. In this case it already did because had I known about this pin, I would have made sure it was pushed in before I rebuilt it.

http://devestechnet.com/Home/Forgotten261

This is the placement of that pin on my engine now:

http://forums.devestechnet.com/filedata/fetch?photoid=1197&type=large

If you have the oil pan and off you can look in the oil hole and see if the passage is open or not. for full flow oil filtering you must block the vertical passage between the two large oil ports.

If you need to remove the dowel pin I would drill and tap it 1/4-20, apply some heat around the area and use a slide hammer to coax it out. Instead of driving an old pin in to block the flow it is probably safer to remove and use a new pin (if necessary) and some sealer.

Grigg

So my question now is, if the magic, unmovable pin is in the bypass position, then can you plug the two filter lines without starving the engine of oil and roasting its innards?
Carl

Yes

If the 261 came from the factory with the "pin/plug" moved and the full-flow oil filter installed, woe will be unto you if you disconnect/plug the oil filter ports/holes on the block.

The other question is: obviously the block was available from the factory with that pin/plug in place - but how/why (as a replacement block/engine)? Standard original-equipment 58-63 engines are shown in Shop Manuals as have the full-flow filter from the factory.

1958 261, for example

1960 261 filter description

Mine is a 59 and the 59 shop manual doesn't mention a word about this. The engine rebuilders that didnt know either have good reputations around these here parts.

So if you were me, would you take about a 3/8" oak dowel and a hammer and whack that sucker a bit to see what resistance you run into, or go with Griggs advice, which means finding a new pin or fabricating one. Before I do that, I sure would like to see what one looks like? I dont even know how far it goes in, or out.

We have more information tonight than we had last night for sure. Wish I had just a LITTLE bit more before messing with Precious!

Deve,

What is the Engine Serial Number on your 261?

Did your 261 come with a full-flow oil filter installed?

Also, what is the block date casting code (and the head date casting code, if you have the 261 head).

Some of us have seen or heard-of factory replacement 261s that had some odd characteristics (Greg Hill, if your read this, please comment on what WD found, if you remember). Maybe a replacement engine came with the plug out in case the engine got installed with no filter?

I am not surprised that an engine rebuild shop would not know about an oddity regarding a relatively uncommon engine made for 4 years. I'd bet they never saw a full-flow filter.

3769925. Captains bars above the starter, with two other numbers CON3 L174 above the starter too. I thought there was always a number stamped on the Distributor flat, but this one doesn't have any numbers there. The head is an 848 so not originally a 261 head. When I took my original 261 to my engine shop, they found cracks in the block and got me a new one, so I have zero information on its history.

I had them clean, magnaflux, bore to .040 over, do the normal prep, turn the crank, etc and then sell me the new pistons, cam, rings, etc, etc. and I did everything myself. So, really wish I had known! Now that its on the frame, tuned and adjusted, bad time to find it.

I think shop manuals remain silent on subjects like the dowels because it was not in the realm of Chevrolet dealers to do total rebuilds. 50 years ago there were hundreds of engine rebuilders around the country and GM considered them competition because they not only did the labor, but they installed aftermarket parts. GM wanted to sell now short blocks. And then there was another competitor of GM... the junk yards. Being a licensed salvage dealer for many years put me in that category. The Hollander states that casting No. 3759365 has the dowel. It clearly states that the doweled block fits all, but "Do not drive in the plug above the oil filter inlet hole. When driven in it is to be used with a full flow oil filter." The 261 was designed to be a truck engine, but the full flow setup just didn't work in trucks that were worked hard because of the rubber hoses under the exhaust became brittle from heat. 261 engines were very popular in their day with the guys that pulled cable dumps, but a lot of them bit the dust when they lost their oil.

Gosh, I'm glad I asked. Now I feel educated and thanks to you guys for taking the time to do so. I appreciate all of you!

However, I have one other question so educate me some more....
From what I'm reading and learning here most of the thread seems to be centered around the 1958-1962 engine. What about the early 261 engine like my 1956.

(my engine is not in my shop right now so I can't look at it for any obvious answer). Does this question fit here or should I delete my post here and start another thread??

The 1954-1957 261 engines were plumbed for use of an optional by-pass oil filter (as used on 235s and 216s).

In case someone asks, the 261 Canadian Pontiac engine used a by-pass oil filter (it never used the full-flow oil filter) and it had hydraulic lifters (I do not know the years this was available).

The 1954 optional 261 Canadian Chevrolet/GMC truck engine was like the 1954 261 USA Chevrolet truck engine. Does anyone know the years in which this engine was available in Canadian trucks?

A 1956 should be casting No. 3836340 and what I read out of it, it doesn't have the dowels. I think your question fits very much into the discussion because you have a 261 and we are discussing serious business, but I'm not a moderator. If yours had a bypass filter or no filter you should be ok. But on any engine rebuild, and probably more so a 261, its a good idea to check for oil circulation before firing them up. Lots of people stick a screw driver blade in the oil pump and turn it. I don't like that because I have seen people reinstall the distributor and not get the distributor in the slot and still starve the thing for oil. I like to pull all the plugs and crank the engine for about 10 second intervals and watch for oil at the rockers. I keep a battery charger on the low position during this cranking. Starters can stand a little too much voltage better than too little.

That block casting code is, as you indicated, a 1958-63 code.

If it is a 1958 or later 261, with a L174 date casting code, it looks like the block was cast in December 1964. If that is correct, it would be a replacement block. That would explain no Engine Serial Number.

Did your engine shop tell you from whom they obtained the block?

Do you have an oil filter on that engine? If so, is it a by-pass or a full-flow; and, into which holes in the block is it plumbed (a photo of the plumbing/line-attachments would be interesting to see)?

Have you attached an oil pressure gauge to the engine while it is running (or, have you not run/broken-in the engine)? If you have run the engine and attached a gauge, where did you attach the sender line and what was the pressure reading?

From 2 different Chevrolet catalogs.

Important:
By-pass plug over front lower case connection
must be in 5/8" when full flow oil flter is used.
Must be flush when by-pass type or no filter is used.

Note:
When Full Flow Oil Filter is used,
the plug located in the cylinder block
just above the oil filter inlet hose hole,
(lower front) must be driven in
5/8" (.63) below the surface of the boss.

It was an empty block when I first saw it Tim with nothing attached. Here are the pics of the side of it..

http://devestechnet.com/Images/Restorations/1950B/D50b00411lg.jpg

http://devestechnet.com/Images/Restorations/1950B/D50b00038lg.jpg

http://forums.devestechnet.com/filedata/fetch?photoid=1197&type=large

The pipe with the T connector came with it, so I just used it the way I got it. Oil pressure is off the T. The engine shop didn't tell me where they got it, and I am sure if I called and asked he wouldn't know because its been over 10 years. If I find anything out I'll let you know.

Oil pressure is great. Good flow to the rockers, no complaints about how it runs at all. I wanted hydraulic lifters in this build, so got the proper cam, rods, lifters, etc to do that. Very happy with how it turned out. 5/8"? Really? Thats a long ways!!

Sure looks like the oil plug is out, and therefore not forcing the oil to go through the filter.

Grigg

Where do you have the oil pressure sender attached, Deve?

Maybe you have a by-pass flow to your oil filter. That would still all oil to reach other parts of the engine. It is OK to have by-pass lubrication. Normally, the by-pass hose would be connected to the smaller diameter port to the left of the port you are using.

Here is an additional fact to add to the confusion: the full-flow filter/plumbing oil-flow direction is from left-port on block to right-port on block.

If you have not seen the "flow photo" from a Shop Manual, I'll post a link later today.

The way the photo shows it, there will be virtually no flow through those large-diameter lines with the dowel pin in the "out" position. There will be almost equal oil pressure to both sides of the filter. Filter elements will take a LONG time to get dirty, however!
Jerry

Coupla things.. Tom, can you take a picture, or scan or give us an idea of exactly where you got those .63 (5/8") numbers? That would make me feel a little better.

Also, if it was your engine everyone, would you try to push that pin in? Or try to take it out? Or leave it alone? I am on the fence here. The engine was thoroughly gone over and cleaned really well inside and out. Since its an oil galley part, maybe its lubricated enough to move? How hard do I hit it?

Below is todays photos of this engine. This is not its first rodeo because they had to bore it to 40 over. I will be writing about this fiasco, so added the number pics too.

Tim, where did you go to confirm the numbers on my 1964 261 motor? Ya know, leave it to me to have the one in a gazillion motor!

http://devestechnet.com/Images/Restorations/1950B/D50b00479lg.jpg
http://devestechnet.com/Images/Restorations/1950B/D50b00480lg.jpg
http://devestechnet.com/Images/Restorations/1950B/D50b00481lg.jpg
http://devestechnet.com/Images/Restorations/1950B/D50b00482lg.jpg
http://devestechnet.com/Images/Restorations/1950B/D50b00483lg.jpg
http://devestechnet.com/Images/Restorations/1950B/D50b00484lg.jpg
http://devestechnet.com/Images/Restorations/1950B/D50b00485lg.jpg
http://devestechnet.com/Images/Restorations/1950B/D50b00486lg.jpg

Thanks everyone!

Good news is, as it stands, the motor runs nice, good pressure (right at 30), good flow. The only problem is my full flow filter will last forever and the engine oil won't get the filtering benefit.

If the pin is in the bypass position in Deve's picture, and the filter is full flow, wouldn't his oil pressure suffer unless the filter housing is restricted.

Isn't that why the bypass filters have a restriction in the line to limit the amount of oil going through the filter?

The big ports don't bypass. If the big hole on the lower gallery was plugged and a small line was installed to the port beside it, the oil would bypass to the pan and a restrictor would be needed if the full flow canister was being used. Right now that big filter with the 1/2" ID lines is just eye candy- - -virtually no flow through it.
Jerry

So there is a small port just next to the large port. Thats the bypass port, but there should be two of them, so does that mean the other side just uses the 1/2" port?

Yes- - - -small port is a drain back into the oil pan, with no pressure on it. With the dowel in the "out" position, both of the large ports receive the output of the oil pump. Either one could be used as a supply point to the bypass filter, with the return line going to the small port to the left of the lower 1/2" port.

Once the dowel is pushed in, the lower big port becomes the oil filter supply point, with the filter output going to the upper large port and from there to the engine. That puts the filter in series with the entire flow of the pump and the drain back into the pan is not used. If the engine is run without a filter and the "full flow" dowel is pushed in, a jumper line between the 1/2" ports MUST be installed.

I have a late model 261 engine in my shop. I'll look at the plumbing ports and confirm that I've got the flow visualized properly.
Jerry

Thanks. Tim please do link the issue of flow direction.

I am adding a lot of info to the how-to article, and also would like to know how to drill those 6 water jacket holes in the head.

Place the head gasket for a 261 on the head and mark the holes for placement? Then drill a ?? size hole at a ?? angle in the head ?? deep. How about beveling the holes? Concerns when doing it? etc.

Also, the 848 head (not sure the full number) is a higher compression head I believe than the other numbered 235 heads, but is it the SAME as the native 261 850 head?

Just checked a 216, 235, and a 261 with the dowel pin. The return hole near the pan rail is in the same place on all of them- - -the same position as the small plugged port next to the 1/2" NPT lower hole on the 261. If you want to alter the flow on the engine in the picture to actually do some filtering, adapt the lower line down to fit the small port, plug the big lower hole, and add a Holley carburetor main jet drilled out to 1/16" diameter to the fitting that screws into the 1/8" NPT port. A 1/4-28 tap is close enough to the Holley jet thread to work- - - -I've installed bunches of them for people too lazy to clean out canister filter housings, who insisted on using a spin-on filter in a bypass application.

The 848 head on a 261 will give considerably higher compression than a stock 261 head, even higher than on a 235 because of the extra displacement. The 261's were designed as high-torque truck engines, and nobody wanted to use premium fuel in a working truck.
Jerry

1958-1963+ oil filter flow direction - from the 1959 Shop Manual - Supplement.

Deve,

As Jerry posted, the 261 head resulted in lower compression than found on 235s with the "848" head from 1956-1963. GM/Chevrolet did increase the 261 compression a little between 1954 and 1963, but the 848 head 235s always had higher compression.

If you want the various compression specs for 235s and 261s from 54 (or 56) to 63, let me know. I'll try to look this up next week ("spring"/winter break for me).