The Stovebolt Site Forums The Shop Area Engine Shop 261 Questions

Just installed my 261 engine in my 52 3600 and have come up with a couple of questions.
1. Where on the engine is the connection port for an oil pressure gauge line or sending unit? (This is a full flow oiling system engine) The old engine was a 234 which had the port on the left hand side of the block. I would be interestd in hearing how other Stovebolters running 261's have solved the problem.

2. Timing marks, there are several stamped on the flywheel, three vertical lines a circle and a triangle. I heard of references to a pressed in steel ball but my flywheel has only the three types of marks I've listed. What is the significance of these three different types of marks.?
Later
BUBBAB52

Hi Jim,
I'm taking a guess at this. On my 235 the back left side of the block is were my oil pressure switch goes. It is "tee'd" (3 way fitting)in with the bottom oil return line, from the oil canister.
And the timing mark on mine is a triangle for TDC I believe. Each of those lines is 5 degrees.I forget what the circle is. I hope this helps.

Chevyboy62

Best get an old Manual for yrs that had 261's or bigger trucks that had them or both! Try the www.inliners.org site with question. I have no idea what the "full-flow" part is about, has bigger lines I understand. Isn't there a pipe plug in oil line "bump" on side of block you can remove and put in fitting?

Chevyboy62,
Not sure, but it sounds like you got the oil canister lines connected in reverse flow.
The bottom of your oil canister is the output and should go into the crankcase input, which is at the bottom center of the block, driver side.
The hose from the T-fitting should go into the side of the canister.
If you look closely, the letters IN are stamped right next to the opening.

Jim,

Does your 261 have an oil filter? If so, what does it look like and what size are the lines?

What year is your engine? You state it is full-flow. Have you confirmed the casting numbers are for '58-'62 or are you basing this on features of the engine (like the size of the oil filter inlet/outlet holes in the block)?

Answers to the above question are necessary before advice can be given on where to attach the oil pressure line to the block.
If you have an oil filter on a full-flow engine, the oil pressure line can be attached to any of the fittings at the ends of the inlet/outlet lines. Mine was originally on the inlet side but I have converted to a spin-on filter and have placed the oil-pressure line on the outlet side of the filter base.

If you have a '58-'62 261 that has no oil filter, attaching the oil pressure line to the outlet hole (by relacing the plug in the block) must be done with care. You might want to consider attaching a filter unit and you must make an adjustment to a bypass "valve" in the block - this is important. Maybe someone else has better information on this.

Finally, the 1960 Shop Manual has minimal information on oil pressure sender/gauge but there are references to an electrical sender and a mechanical sender. My engine had a mechanical sender and an accessory oil filter (attached as I described above).

Tim

Isn't it true you need to be very careful with the 261 and the oil filter? Doesn't blocking off the oil filter lines ruin the engine?

Yes, it is my understanding that once an oil filter has been properly installed on a '58-'62 261, blocking of the oil filter line would stop the oil flow.

Tim

So Jim ought to be aware of that fact and check things out before starting up the engine.

Tim's right. On a "full flow" filter, all of the oil from the pump goes through the filter. Plug it and you get no oil flow, so you better have a lot of that slick 50 oil treatment like they have in the commercials.

Tim was right?

Hi Siegmund52,
Now that you mention it..... I looked at how the lines are hooked up. The oil line that comes out from the middle of block goes to the bottom of the oil canister. The other oil line comes from the back of the block, were the oil pressure switch is + goes to the top of the side of the oil canister. I didn't see were the in, or out is. too dirty to tell.
I could post a few close up pics of how the oil lines are ran. I'm not for sure if this how they are supposed to be ran. PO did alot of wierd things to this truck. Also does anyone know were I can get replacement oil lines?

Chevyboy62

This is a photo of a stock full flow 261 with the factory filter.This engine was originally pulled out of 62 big truck.The feed port to the filter on a full flow engine is the lower front oil port.The return line goes to the rear oil port.This engine had no place for an oil guage, notice where I tapped the filter elbow for the guage tube. My other full flow 261 uses an after market spin on filter set up.Theres a small dowel near an oil port, that supposedly must be in the "out" position to open a internal bypass if the engine is going to be run filterless. 261 filter

Bolters:
Thanks for all the information.
Front port out to filter.
Back port return from filter to block.
Gotcha!
BUBBAB52

Chevyboy62,
So your connection is right after all.... :p

Your lines are connected properly for the bypass cannister.
You can buy a brand new set of oil filter lines at www.chevyduty.com for $24. They will fit the cannister with the input on the right side.

There is another cannister (same style, but with the input on the left side), which was bolted to the right side of the manifold (for other vehicles without the gearbox right next to the manifold).
For this one the input oil line from ChevyDuty will be too short by a few inches and you have to make a 1/4 brass extension pipe with fittings.

www.stovebolt.com/techtips/full_pressure.htm shows the conversion of a 235 to full-pressure-filter.
But I believe it will lower the oil pressure somewhat.
If you change your oil regularly (2-3 times a year for a daily driver, using the same brand oil) and don't run the engine on high rpm all the time, the bypass filter is just fine.
Plus with a full-pressure-filter you can blow up your engine if it ever fails to work properly...

The thing I like about the 235 is that is so simple with little that can go wrong.
Introducing more features also increases the chances of something going wrong with them.
Just look at all the modern high tech vehicles with their 'improvements' :rolleyes:
One day everything is fine - next day you are on the side of the freeway with a tiny problem that disables the entire system...