The Stovebolt Site Forums The Shop Area Engine Shop 261 full flow questions

Hello everybody I am working on a 261 engine for a friend of mine how do I know if this engine needs to have the full flow oil system or not I am not too familiar with this motor right now it does not have anything and supposedly he was having a problem getting oil up to the rocker arms I will be headed to his place on Saturday morning to see if I could prime the oil pump and get oil to the top.
The engine has been rebuilt about four or five years ago and he just recently said it in his car and is trying to get it going but the guy who worked on it before told him no oil was reaching to the top it looks like the plugs on the side of the block under the intake manifold are plugged any help is really appreciated thank you

There are two different oil circuits on a 261, depending on the year of manufacture. Can you post the casting number, located on the lower passenger's side of the block near the fuel pump, and/or the stamped ID number, located on a machined pad to the rear of the distributor? If there are two large 1/2" pipe threaded ports on the driver's side of the engine near the oil pan rail, you have a late model (1959-63) engine that can be set up for full-flow oil filtering. If that one is not configured properly, the entire lubricating system can be starved for oil, not just the cylinder head. Don't try to run it until you give us some more information!
Jerry

Lots of good info here:

http://devestechnet.com/home/thevenerable261

Ok thank you I will try later on this evening here is the cast number 3769717

3769717 was used on 1959-1962 Chevrolet 261 truck engines.

Find and post the head & block date casting codes shown on this page.

I see a F030ILB
On the deck near starter

I think that LC in the engine serial number indicates an engine on a C60 truck (with RPO 225 )

I will look up that RPO - my browser keeps crashing when I try to read it online.

Can you post the block and the head date casting codes?

I have the motor put together and in the car hard to see and read it.
But the two plugs seem to be 1/2 inch

Can you just run a hose from the one fitting to the other on the driver side of the block if I get a hose made or does anyone make them already.

I actually relocated my oil filter to the inner fender, therefore hoses were obviously short. I figured my length and took my old hose ends to my hydraulic hose maker guy that makes hoses for my towtruck. Worked out great and they make em while you wait.

Should I just buy one of those aftermarket oil filter relocate setups

Don't do anything (including starting the engine) until you can figure out whether it's set up for full flow or bypass filtering. Read and understand the tech tip on how to tell the difference. Near the forward large oil port on the driver's side there is a round dowel pin pressed into the block. If it's flush with the outside of the block, you have a "bypass" oil system that routes most of the oil pump output to the engine without going through a filter. If the dowel is driven inward about 1/2" or a little more, the oil has to exit the block at the forward port, go through a filter, and re-enter the engine at the upper large port. This is the "full flow" option that was used with a large filter canister with 1/2" inside diameter flex lines. Don't do ANYTHING else until you determine which way the oil system is set up to work.
Jerry

I have full flow so I bought a pricey Moroso adapter and used U-bolts to attach it to the manifold in the original location. It uses a NAPA 1072 spin-on filter which has a bypass valve (I think). The picture shows an extra line to a 2nd pressure gauge because I wanted info about pressure before and after the filter when starting up. (That didn't work because the 2 gauges had different response times.)

Okay I'll try and take a look at the pin thanks again
That's a clean setup Wally

Here it is

OK- - - -it looks like the dowel is either pushed in to the "full flow" position, or it's missing altogether. The oil passage behind the plug immediately beneath that dowel is drilled into the output gallery from the oil pump. If the dowel was in the "out" position, the oil could flow upwards to the raised area that contains the front to rear oil gallery that feeds the main bearings. In its current position, the oil must flow out of the block, through some type of full flow oil filter, and enter the main oil gallery through the other large opening further back on the block. If you choose not to run an oil filter, the two large ports must be connected with either hard pipe or a 1/2" diameter flex line.

The original full flow canister was about 5 inches in diameter and close to a foot long. Those canisters are a little hard to find, and so are the filter elements. You can substitute an aftermarket filter adapter and a spin-on filter, as long as the lines to and from the block are large enough to carry enough oil to lubricate the engine. If the filter is attached to the intake manifold you can use 1/2" OD tubing and brass fittings. If the filter is mounted on the fender well, you'll need flex hoses to accommodate engine torque. Be sure to route flex hoses as far away from the exhaust pipe as possible. A heat damaged flex line will empty the oil in a few seconds.
Jerry

Looks like the dowel is pressed in, which means the block is set for full flow filtration. With the oil ports plugged, the bearings and upper end are not getting oil properly. It is imperative to connect the two ports - minimum of 1/2" ID hose or tubing - for a block in that configuration, whether or not a full-flow filter is used.

Somewhere I have the factory drawing of the 261 full-flow filter setup... need to do some digging to find it.

Doug

Thank you guys very much
Have a great evening
I will keep ya posted when I get to it

The pic is from my Motors Truck Repair manual. Is this the full flow version? I'm far removed from the book and don't know the publication date.

Wally,

That is an illustration of a by-pass filter assembly (235/261 engine/block).

That diagram also shows the late model oil circuit used on engines with hydraulic valve lifters.
Jerry

Thanks, Jerry

What year USA or Canadian 261s (cars and/or trucks) had hydraulic lifters (from the factory)?

"The 1955—1962 Canadian full-size Pontiac car had a standard 261-cubic-inch engine that had hydraulic lifters. This engine was not sold in the US, but was very similar to the US truck 261."

That might be the answer to my question to Jerry? (found here)

I believe the only 261's equipped with hydraulic lifters were "Pontiac" automobile engines in Canada. Maybe one of our friends north of the border can confirm that? I'm working on a deep hole drilling guide similar to the fixture used to bore a gun barrel blank to put a lifter oil gallery in any stovebolt engine, 216, 235, or 261.
jerry

Wasn't able to get to it this past weekend
I'm hoping for this Saturday
Going to get a hose made during the week
Stay tuned

With a little creative plumbing, you can join the two ports with plain old 1/2" black water pipe (Don't use galvanized!) or brass pipe nipples. Another option would be 1/2" hard copper pipe, which has a 5/8" outside diameter, and is available at any hardware store, along with a variety of fittings for both ends.
Jerry

I'm currently at this plumbing stage with my 1967 crate 261 build. I have bypass oiling (plug out).

On my 235 I had a .062" restrictor in the oiling system.

Can someone confirm I need to use a restrictor in my 261 bypass oiling system as well to retain pressure.

Yes, any bypass filter needs a restrictor. It's built into the standpipe of the original canister filter like a Fram or AC. If I'm using a spin-on adapter for that vastly inferior type of filter for some reason, I adapt a Holley carburetor main jet to one of the fittings upstream of the filter. If a customer insists on the spin-on over my objections, that's how it needs to be done. I absolutely will not run that type of filter on an engine I build for myself, unless I'm using a much finer-mesh filter media than is usually used for engine oil. Some spin on ilters for hydraulic fluid have a 1-micron rating instead of the 10-20 micron size that's generally used on a full flow filter. A Diesel fuel filter for an 18 wheeler engine also works well in a bypass configuration for engine oil on a stovebolt.
Jerry

thanks. I plan to plumb the lines per my photo above using a spin-on. I stopped using a canister filter due to space limitations caused by my master cylinder.

The canister filter fits OK on the front of the intake manifold, or on the inner fender. I modify the canisters to run the Frantz-style toilet paper roll as a bypass filter, and run a spin-on full flow filter as well on some engines to catch the "rocks, marbles, and bowling balls" that could damage bearings.
Jerry

Where do you connect and place/mount the spin-on full-flow oil filter, Jerry?

On the 261, the dowel pin has to be pushed in for full flow filtering, and the bypass filter is tapped off anywhere with full oil pressure. On a 235, the oil gallery has to be modified for full flow by plugging the oil pump output passageway below the main oil gallery and drilling and tapping a couple of large diameter ports, either 3/8" NPT or 1/2" NPT. A 3/8" fitting will carry enough oil volume to support a full flow filter and supply the engine with enough oil to keep it lubed. !/2" was a bit of overkill on the part of Chevy when they built the late model 261.

A spin on adapter fits nicely on the driver's side inner fender with single braid flex lines in and out.
Jerry

Just to add to this great thread. I picked up a 261 a couple years back and had it machined and I assembled it to put in my 53. The engine was originally in a 1962 cab forward truck, it was delivered in the bypass mode. So the point Im trying to make is Hot Rod is right make sure you know first how it was configured, dont assume one or the other without making sure. In my case, I could of just plugged the oil ports but I decided to use a bypass filter setup, but could of easily ran it without a filter and plugged the exterior oil port with pipe plugs
and changed oil on a tighter interval.

Just a bit of clarification. If the 261 dowel pin is pushed in, the 1/2" pipe ports MUST be connected in some way- - - -either by running through a full flow fliter, or with a pipe or a flex line. Plugging the ports without pulling the dowel back out in some way will result in an engine life measured in minutes, since none of the bearings will get any oil!
Jerry

Happy Saturday
Well got the hose in and I primed the engine and what do ya know oil to the rocker arms are flowing.
Thanks guys for all the information and help
Now to do I bit of everything else now
Fluids gas coolant etc and see if I can set the timing and so on..

One of the 261's I've got stockpiled is the late model with the dowel pin. I'm planning to drill and tap the dowel so i can pull it out with a slide hammer, a jack screw, or something similar, and thread the hole so the passageway can be opened or closed with a screw-in plug instead of a pressed-in dowel. I'll feel a lot more comfortable with a threaded plug and a lock nut controlling the oil flow!
Jerry